Classification - Machine Learning This is ‘Classification’ tutorial which is a part of the Machine Learning course offered by Simplilearn. We will learn Classification algorithms, types of classification algorithms, support vector machines(SVM), Naive Bayes, Decision Tree and Random Forest Classifier in this tutorial. Objectives Let us look at some of the objectives covered under this section of Machine Learning tutorial. Define Classification and list its algorithms Describe Logistic Regression and Sigmoid Probability Explain K-Nearest Neighbors and KNN classification Understand Support Vector Machines, Polynomial Kernel, and Kernel Trick Analyze Kernel Support Vector Machines with an example Implement the Naïve Bayes Classifier Demonstrate Decision Tree Classifier Describe Random Forest Classifier Classification: Meaning Classification is a type of supervised learning. It specifies the class to which data elements belong to and is best used when the output has finite and discrete values. It predicts a class for an input variable as well. There are 2 types of Classification: Binomial Multi-Class Classification: Use Cases Some of the key areas where classification cases are being used: To find whether an email received is a spam or ham To identify customer segments To find if a bank loan is granted To identify if a kid will pass or fail in an examination Classification: Example Social media sentiment analysis has two potential outcomes, positive or negative, as displayed by the chart given below. https://www.simplilearn.com/ice9/free_resources_article_thumb/classification-example-machine-learning.JPG This chart shows the classification of the Iris flower dataset into its three sub-species indicated by codes 0, 1, and 2. https://www.simplilearn.com/ice9/free_resources_article_thumb/iris-flower-dataset-graph.JPG The test set dots represent the assignment of new test data points to one class or the other based on the trained classifier model. Types of Classification Algorithms Let’s have a quick look into the types of Classification Algorithm below. Linear Models Logistic Regression Support Vector Machines Nonlinear models K-nearest Neighbors (KNN) Kernel Support Vector Machines (SVM) Naïve Bayes Decision Tree Classification Random Forest Classification Logistic Regression: Meaning Let us understand the Logistic Regression model below. This refers to a regression model that is used for classification. This method is widely used for binary classification problems. It can also be extended to multi-class classification problems. Here, the dependent variable is categorical: y ϵ {0, 1} A binary dependent variable can have only two values, like 0 or 1, win or lose, pass or fail, healthy or sick, etc In this case, you model the probability distribution of output y as 1 or 0. This is called the sigmoid probability (σ). If σ(θ Tx) > 0.5, set y = 1, else set y = 0 Unlike Linear Regression (and its Normal Equation solution), there is no closed form solution for finding optimal weights of Logistic Regression. Instead, you must solve this with maximum likelihood estimation (a probability model to detect the maximum likelihood of something happening). It can be used to calculate the probability of a given outcome in a binary model, like the probability of being classified as sick or passing an exam. https://www.simplilearn.com/ice9/free_resources_article_thumb/logistic-regression-example-graph.JPG Sigmoid Probability The probability in the logistic regression is often represented by the Sigmoid function (also called the logistic function or the S-curve): https://www.simplilearn.com/ice9/free_resources_article_thumb/sigmoid-function-machine-learning.JPG In this equation, t represents data values * the number of hours studied and S(t) represents the probability of passing the exam. Assume sigmoid function: https://www.simplilearn.com/ice9/free_resources_article_thumb/sigmoid-probability-machine-learning.JPG g(z) tends toward 1 as z -> infinity , and g(z) tends toward 0 as z -> infinity K-nearest Neighbors (KNN) K-nearest Neighbors algorithm is used to assign a data point to clusters based on similarity measurement. It uses a supervised method for classification. The steps to writing a k-means algorithm are as given below: https://www.simplilearn.com/ice9/free_resources_article_thumb/knn-distribution-graph-machine-learning.JPG Choose the number of k and a distance metric. (k = 5 is common) Find k-nearest neighbors of the sample that you want to classify Assign the class label by majority vote. KNN Classification A new input point is classified in the category such that it has the most number of neighbors from that category. For example: https://www.simplilearn.com/ice9/free_resources_article_thumb/knn-classification-machine-learning.JPG Classify a patient as high risk or low risk. Mark email as spam or ham. Keen on learning about Classification Algorithms in Machine Learning? Click here! Support Vector Machine (SVM) Let us understand Support Vector Machine (SVM) in detail below. SVMs are classification algorithms used to assign data to various classes. They involve detecting hyperplanes which segregate data into classes. SVMs are very versatile and are also capable of performing linear or nonlinear classification, regression, and outlier detection. Once ideal hyperplanes are discovered, new data points can be easily classified. https://www.simplilearn.com/ice9/free_resources_article_thumb/support-vector-machines-graph-machine-learning.JPG The optimization objective is to find “maximum margin hyperplane” that is farthest from the closest points in the two classes (these points are called support vectors). In the given figure, the middle line represents the hyperplane. SVM Example Let’s look at this image below and have an idea about SVM in general. Hyperplanes with larger margins have lower generalization error. The positive and negative hyperplanes are represented by: https://www.simplilearn.com/ice9/free_resources_article_thumb/positive-negative-hyperplanes-machine-learning.JPG Classification of any new input sample xtest : If w0 + wTxtest > 1, the sample xtest is said to be in the class toward the right of the positive hyperplane. If w0 + wTxtest < -1, the sample xtest is said to be in the class toward the left of the negative hyperplane. When you subtract the two equations, you get: https://www.simplilearn.com/ice9/free_resources_article_thumb/equation-subtraction-machine-learning.JPG Length of vector w is (L2 norm length): https://www.simplilearn.com/ice9/free_resources_article_thumb/length-of-vector-machine-learning.JPG You normalize with the length of w to arrive at: https://www.simplilearn.com/ice9/free_resources_article_thumb/normalize-equation-machine-learning.JPG SVM: Hard Margin Classification Given below are some points to understand Hard Margin Classification. The left side of equation SVM-1 given above can be interpreted as the distance between the positive (+ve) and negative (-ve) hyperplanes; in other words, it is the margin that can be maximized. Hence the objective of the function is to maximize with the constraint that the samples are classified correctly, which is represented as : https://www.simplilearn.com/ice9/free_resources_article_thumb/hard-margin-classification-machine-learning.JPG This means that you are minimizing ‖w‖. This also means that all positive samples are on one side of the positive hyperplane and all negative samples are on the other side of the negative hyperplane. This can be written concisely as : https://www.simplilearn.com/ice9/free_resources_article_thumb/hard-margin-classification-formula.JPG Minimizing ‖w‖ is the same as minimizing. This figure is better as it is differentiable even at w = 0. The approach listed above is called “hard margin linear SVM classifier.” SVM: Soft Margin Classification Given below are some points to understand Soft Margin Classification. To allow for linear constraints to be relaxed for nonlinearly separable data, a slack variable is introduced. (i) measures how much ith instance is allowed to violate the margin. The slack variable is simply added to the linear constraints. https://www.simplilearn.com/ice9/free_resources_article_thumb/soft-margin-calculation-machine-learning.JPG Subject to the above constraints, the new objective to be minimized becomes: https://www.simplilearn.com/ice9/free_resources_article_thumb/soft-margin-calculation-formula.JPG You have two conflicting objectives now—minimizing slack variable to reduce margin violations and minimizing to increase the margin. The hyperparameter C allows us to define this trade-off. Large values of C correspond to larger error penalties (so smaller margins), whereas smaller values of C allow for higher misclassification errors and larger margins. https://www.simplilearn.com/ice9/free_resources_article_thumb/machine-learning-certification-video-preview.jpg SVM: Regularization The concept of C is the reverse of regularization. Higher C means lower regularization, which increases bias and lowers the variance (causing overfitting). https://www.simplilearn.com/ice9/free_resources_article_thumb/concept-of-c-graph-machine-learning.JPG IRIS Data Set The Iris dataset contains measurements of 150 IRIS flowers from three different species: Setosa Versicolor Viriginica Each row represents one sample. Flower measurements in centimeters are stored as columns. These are called features. IRIS Data Set: SVM Let’s train an SVM model using sci-kit-learn for the Iris dataset: https://www.simplilearn.com/ice9/free_resources_article_thumb/svm-model-graph-machine-learning.JPG Nonlinear SVM Classification There are two ways to solve nonlinear SVMs: by adding polynomial features by adding similarity features Polynomial features can be added to datasets; in some cases, this can create a linearly separable dataset. https://www.simplilearn.com/ice9/free_resources_article_thumb/nonlinear-classification-svm-machine-learning.JPG In the figure on the left, there is only 1 feature x1. This dataset is not linearly separable. If you add x2 = (x1)2 (figure on the right), the data becomes linearly separable. Polynomial Kernel In sci-kit-learn, one can use a Pipeline class for creating polynomial features. Classification results for the Moons dataset are shown in the figure. https://www.simplilearn.com/ice9/free_resources_article_thumb/polynomial-kernel-machine-learning.JPG Polynomial Kernel with Kernel Trick Let us look at the image below and understand Kernel Trick in detail. https://www.simplilearn.com/ice9/free_resources_article_thumb/polynomial-kernel-with-kernel-trick.JPG For large dimensional datasets, adding too many polynomial features can slow down the model. You can apply a kernel trick with the effect of polynomial features without actually adding them. The code is shown (SVC class) below trains an SVM classifier using a 3rd-degree polynomial kernel but with a kernel trick. https://www.simplilearn.com/ice9/free_resources_article_thumb/polynomial-kernel-equation-machine-learning.JPG The hyperparameter coefθ controls the influence of high-degree polynomials. Kernel SVM Let us understand in detail about Kernel SVM. Kernel SVMs are used for classification of nonlinear data. In the chart, nonlinear data is projected into a higher dimensional space via a mapping function where it becomes linearly separable. https://www.simplilearn.com/ice9/free_resources_article_thumb/kernel-svm-machine-learning.JPG In the higher dimension, a linear separating hyperplane can be derived and used for classification. A reverse projection of the higher dimension back to original feature space takes it back to nonlinear shape. As mentioned previously, SVMs can be kernelized to solve nonlinear classification problems. You can create a sample dataset for XOR gate (nonlinear problem) from NumPy. 100 samples will be assigned the class sample 1, and 100 samples will be assigned the class label -1. https://www.simplilearn.com/ice9/free_resources_article_thumb/kernel-svm-graph-machine-learning.JPG As you can see, this data is not linearly separable. https://www.simplilearn.com/ice9/free_resources_article_thumb/kernel-svm-non-separable.JPG You now use the kernel trick to classify XOR dataset created earlier. https://www.simplilearn.com/ice9/free_resources_article_thumb/kernel-svm-xor-machine-learning.JPG Naïve Bayes Classifier What is Naive Bayes Classifier? Have you ever wondered how your mail provider implements spam filtering or how online news channels perform news text classification or even how companies perform sentiment analysis of their audience on social media? All of this and more are done through a machine learning algorithm called Naive Bayes Classifier. Naive Bayes Named after Thomas Bayes from the 1700s who first coined this in the Western literature. Naive Bayes classifier works on the principle of conditional probability as given by the Bayes theorem. Advantages of Naive Bayes Classifier Listed below are six benefits of Naive Bayes Classifier. Very simple and easy to implement Needs less training data Handles both continuous and discrete data Highly scalable with the number of predictors and data points As it is fast, it can be used in real-time predictions Not sensitive to irrelevant features Bayes Theorem We will understand Bayes Theorem in detail from the points mentioned below. According to the Bayes model, the conditional probability P(Y|X) can be calculated as: P(Y|X) = P(X|Y)P(Y) / P(X) This means you have to estimate a very large number of P(X|Y) probabilities for a relatively small vector space X. For example, for a Boolean Y and 30 possible Boolean attributes in the X vector, you will have to estimate 3 billion probabilities P(X|Y). To make it practical, a Naïve Bayes classifier is used, which assumes conditional independence of P(X) to each other, with a given value of Y. This reduces the number of probability estimates to 2*30=60 in the above example. Naïve Bayes Classifier for SMS Spam Detection Consider a labeled SMS database having 5574 messages. It has messages as given below: https://www.simplilearn.com/ice9/free_resources_article_thumb/naive-bayes-spam-machine-learning.JPG Each message is marked as spam or ham in the data set. Let’s train a model with Naïve Bayes algorithm to detect spam from ham. The message lengths and their frequency (in the training dataset) are as shown below: https://www.simplilearn.com/ice9/free_resources_article_thumb/naive-bayes-spam-spam-detection.JPG Analyze the logic you use to train an algorithm to detect spam: Split each message into individual words/tokens (bag of words). Lemmatize the data (each word takes its base form, like “walking” or “walked” is replaced with “walk”). Convert data to vectors using scikit-learn module CountVectorizer. Run TFIDF to remove common words like “is,” “are,” “and.” Now apply scikit-learn module for Naïve Bayes MultinomialNB to get the Spam Detector. This spam detector can then be used to classify a random new message as spam or ham. Next, the accuracy of the spam detector is checked using the Confusion Matrix. For the SMS spam example above, the confusion matrix is shown on the right. Accuracy Rate = Correct / Total = (4827 + 592)/5574 = 97.21% Error Rate = Wrong / Total = (155 + 0)/5574 = 2.78% https://www.simplilearn.com/ice9/free_resources_article_thumb/confusion-matrix-machine-learning.JPG Although confusion Matrix is useful, some more precise metrics are provided by Precision and Recall. https://www.simplilearn.com/ice9/free_resources_article_thumb/precision-recall-matrix-machine-learning.JPG Precision refers to the accuracy of positive predictions. https://www.simplilearn.com/ice9/free_resources_article_thumb/precision-formula-machine-learning.JPG Recall refers to the ratio of positive instances that are correctly detected by the classifier (also known as True positive rate or TPR). https://www.simplilearn.com/ice9/free_resources_article_thumb/recall-formula-machine-learning.JPG Precision/Recall Trade-off To detect age-appropriate videos for kids, you need high precision (low recall) to ensure that only safe videos make the cut (even though a few safe videos may be left out). The high recall is needed (low precision is acceptable) in-store surveillance to catch shoplifters; a few false alarms are acceptable, but all shoplifters must be caught. Learn about Naive Bayes in detail. Click here! Decision Tree Classifier Some aspects of the Decision Tree Classifier mentioned below are. Decision Trees (DT) can be used both for classification and regression. The advantage of decision trees is that they require very little data preparation. They do not require feature scaling or centering at all. They are also the fundamental components of Random Forests, one of the most powerful ML algorithms. Unlike Random Forests and Neural Networks (which do black-box modeling), Decision Trees are white box models, which means that inner workings of these models are clearly understood. In the case of classification, the data is segregated based on a series of questions. Any new data point is assigned to the selected leaf node. https://www.simplilearn.com/ice9/free_resources_article_thumb/decision-tree-classifier-machine-learning.JPG Start at the tree root and split the data on the feature using the decision algorithm, resulting in the largest information gain (IG). This splitting procedure is then repeated in an iterative process at each child node until the leaves are pure. This means that the samples at each node belonging to the same class. In practice, you can set a limit on the depth of the tree to prevent overfitting. The purity is compromised here as the final leaves may still have some impurity. The figure shows the classification of the Iris dataset. https://www.simplilearn.com/ice9/free_resources_article_thumb/decision-tree-classifier-graph.JPG IRIS Decision Tree Let’s build a Decision Tree using scikit-learn for the Iris flower dataset and also visualize it using export_graphviz API. https://www.simplilearn.com/ice9/free_resources_article_thumb/iris-decision-tree-machine-learning.JPG The output of export_graphviz can be converted into png format: https://www.simplilearn.com/ice9/free_resources_article_thumb/iris-decision-tree-output.JPG Sample attribute stands for the number of training instances the node applies to. Value attribute stands for the number of training instances of each class the node applies to. Gini impurity measures the node’s impurity. A node is “pure” (gini=0) if all training instances it applies to belong to the same class. https://www.simplilearn.com/ice9/free_resources_article_thumb/impurity-formula-machine-learning.JPG For example, for Versicolor (green color node), the Gini is 1-(0/54)2 -(49/54)2 -(5/54) 2 ≈ 0.168 https://www.simplilearn.com/ice9/free_resources_article_thumb/iris-decision-tree-sample.JPG Decision Boundaries Let us learn to create decision boundaries below. For the first node (depth 0), the solid line splits the data (Iris-Setosa on left). Gini is 0 for Setosa node, so no further split is possible. The second node (depth 1) splits the data into Versicolor and Virginica. If max_depth were set as 3, a third split would happen (vertical dotted line). https://www.simplilearn.com/ice9/free_resources_article_thumb/decision-tree-boundaries.JPG For a sample with petal length 5 cm and petal width 1.5 cm, the tree traverses to depth 2 left node, so the probability predictions for this sample are 0% for Iris-Setosa (0/54), 90.7% for Iris-Versicolor (49/54), and 9.3% for Iris-Virginica (5/54) CART Training Algorithm Scikit-learn uses Classification and Regression Trees (CART) algorithm to train Decision Trees. CART algorithm: Split the data into two subsets using a single feature k and threshold tk (example, petal length < “2.45 cm”). This is done recursively for each node. k and tk are chosen such that they produce the purest subsets (weighted by their size). The objective is to minimize the cost function as given below: https://www.simplilearn.com/ice9/free_resources_article_thumb/cart-training-algorithm-machine-learning.JPG The algorithm stops executing if one of the following situations occurs: max_depth is reached No further splits are found for each node Other hyperparameters may be used to stop the tree: min_samples_split min_samples_leaf min_weight_fraction_leaf max_leaf_nodes Gini Impurity or Entropy Entropy is one more measure of impurity and can be used in place of Gini. https://www.simplilearn.com/ice9/free_resources_article_thumb/gini-impurity-entrophy.JPG It is a degree of uncertainty, and Information Gain is the reduction that occurs in entropy as one traverses down the tree. Entropy is zero for a DT node when the node contains instances of only one class. Entropy for depth 2 left node in the example given above is: https://www.simplilearn.com/ice9/free_resources_article_thumb/entrophy-for-depth-2.JPG Gini and Entropy both lead to similar trees. DT: Regularization The following figure shows two decision trees on the moons dataset. https://www.simplilearn.com/ice9/free_resources_article_thumb/dt-regularization-machine-learning.JPG The decision tree on the right is restricted by min_samples_leaf = 4. The model on the left is overfitting, while the model on the right generalizes better. Random Forest Classifier Let us have an understanding of Random Forest Classifier below. A random forest can be considered an ensemble of decision trees (Ensemble learning). Random Forest algorithm: Draw a random bootstrap sample of size n (randomly choose n samples from the training set). Grow a decision tree from the bootstrap sample. At each node, randomly select d features. Split the node using the feature that provides the best split according to the objective function, for instance by maximizing the information gain. Repeat the steps 1 to 2 k times. (k is the number of trees you want to create, using a subset of samples) Aggregate the prediction by each tree for a new data point to assign the class label by majority vote (pick the group selected by the most number of trees and assign new data point to that group). Random Forests are opaque, which means it is difficult to visualize their inner workings. https://www.simplilearn.com/ice9/free_resources_article_thumb/random-forest-classifier-graph.JPG However, the advantages outweigh their limitations since you do not have to worry about hyperparameters except k, which stands for the number of decision trees to be created from a subset of samples. RF is quite robust to noise from the individual decision trees. Hence, you need not prune individual decision trees. The larger the number of decision trees, the more accurate the Random Forest prediction is. (This, however, comes with higher computation cost). Key Takeaways Let us quickly run through what we have learned so far in this Classification tutorial. Classification algorithms are supervised learning methods to split data into classes. They can work on Linear Data as well as Nonlinear Data. Logistic Regression can classify data based on weighted parameters and sigmoid conversion to calculate the probability of classes. K-nearest Neighbors (KNN) algorithm uses similar features to classify data. Support Vector Machines (SVMs) classify data by detecting the maximum margin hyperplane between data classes. Naïve Bayes, a simplified Bayes Model, can help classify data using conditional probability models. Decision Trees are powerful classifiers and use tree splitting logic until pure or somewhat pure leaf node classes are attained. Random Forests apply Ensemble Learning to Decision Trees for more accurate classification predictions. Conclusion This completes ‘Classification’ tutorial. In the next tutorial, we will learn 'Unsupervised Learning with Clustering.'

NOTICE This repository contains the public FTC SDK for the SKYSTONE (2019-2020) competition season. If you are looking for the current season's FTC SDK software, please visit the new and permanent home of the public FTC SDK: FtcRobotController repository Welcome! This GitHub repository contains the source code that is used to build an Android app to control a FIRST Tech Challenge competition robot. To use this SDK, download/clone the entire project to your local computer. Getting Started If you are new to robotics or new to the FIRST Tech Challenge, then you should consider reviewing the FTC Blocks Tutorial to get familiar with how to use the control system: FTC Blocks Online Tutorial Even if you are an advanced Java programmer, it is helpful to start with the FTC Blocks tutorial, and then migrate to the OnBot Java Tool or to Android Studio afterwards. Downloading the Project If you are an Android Studio programmer, there are several ways to download this repo. Note that if you use the Blocks or OnBot Java Tool to program your robot, then you do not need to download this repository. If you are a git user, you can clone the most current version of the repository: git clone https://github.com/FIRST-Tech-Challenge/SKYSTONE.git Or, if you prefer, you can use the "Download Zip" button available through the main repository page. Downloading the project as a .ZIP file will keep the size of the download manageable. You can also download the project folder (as a .zip or .tar.gz archive file) from the Downloads subsection of the Releases page for this repository. Once you have downloaded and uncompressed (if needed) your folder, you can use Android Studio to import the folder ("Import project (Eclipse ADT, Gradle, etc.)"). Getting Help User Documentation and Tutorials FIRST maintains online documentation with information and tutorials on how to use the FIRST Tech Challenge software and robot control system. You can access this documentation using the following link: SKYSTONE Online Documentation Note that the online documentation is an "evergreen" document that is constantly being updated and edited. It contains the most current information about the FIRST Tech Challenge software and control system. Javadoc Reference Material The Javadoc reference documentation for the FTC SDK is now available online. Click on the following link to view the FTC SDK Javadoc documentation as a live website: FTC Javadoc Documentation Documentation for the FTC SDK is also included with this repository. There is a subfolder called "doc" which contains several subfolders: The folder "apk" contains the .apk files for the FTC Driver Station and FTC Robot Controller apps. The folder "javadoc" contains the JavaDoc user documentation for the FTC SDK. Online User Forum For technical questions regarding the Control System or the FTC SDK, please visit the FTC Technology forum: FTC Technology Forum Release Information Version 5.5 (20200824-090813) Version 5.5 requires Android Studio 4.0 or later. New features Adds support for calling custom Java classes from Blocks OpModes (fixes SkyStone issue #161). Classes must be in the org.firstinspires.ftc.teamcode package. Methods must be public static and have no more than 21 parameters. Parameters declared as OpMode, LinearOpMode, Telemetry, and HardwareMap are supported and the argument is provided automatically, regardless of the order of the parameters. On the block, the sockets for those parameters are automatically filled in. Parameters declared as char or java.lang.Character will accept any block that returns text and will only use the first character in the text. Parameters declared as boolean or java.lang.Boolean will accept any block that returns boolean. Parameters declared as byte, java.lang.Byte, short, java.lang.Short, int, java.lang.Integer, long, or java.lang.Long, will accept any block that returns a number and will round that value to the nearest whole number. Parameters declared as float, java.lang.Float, double, java.lang.Double will accept any block that returns a number. Adds telemetry API method for setting display format Classic Monospace HTML (certain tags only) Adds blocks support for switching cameras. Adds Blocks support for TensorFlow Object Detection with a custom model. Adds support for uploading a custom TensorFlow Object Detection model in the Manage page, which is especially useful for Blocks and OnBotJava users. Shows new Control Hub blink codes when the WiFi band is switched using the Control Hub's button (only possible on Control Hub OS 1.1.2) Adds new warnings which can be disabled in the Advanced RC Settings Mismatched app versions warning Unnecessary 2.4 GHz WiFi usage warning REV Hub is running outdated firmware (older than version 1.8.2) Adds support for Sony PS4 gamepad, and reworks how gamepads work on the Driver Station Removes preference which sets gamepad type based on driver position. Replaced with menu which allows specifying type for gamepads with unknown VID and PID Attempts to auto-detect gamepad type based on USB VID and PID If gamepad VID and PID is not known, use type specified by user for that VID and PID If gamepad VID and PID is not known AND the user has not specified a type for that VID and PID, an educated guess is made about how to map the gamepad Driver Station will now attempt to automatically recover from a gamepad disconnecting, and re-assign it to the position it was assigned to when it dropped If only one gamepad is assigned and it drops: it can be recovered If two gamepads are assigned, and have different VID/PID signatures, and only one drops: it will be recovered If two gamepads are assigned, and have different VID/PID signatures, and BOTH drop: both will be recovered If two gamepads are assigned, and have the same VID/PID signatures, and only one drops: it will be recovered If two gamepads are assigned, and have the same VID/PID signatures, and BOTH drop: neither will be recovered, because of the ambiguity of the gamepads when they re-appear on the USB bus. There is currently one known edge case: if there are two gamepads with the same VID/PID signature plugged in, but only one is assigned, and they BOTH drop, it's a 50-50 chance of which one will be chosen for automatic recovery to the assigned position: it is determined by whichever one is re-enumerated first by the USB bus controller. Adds landscape user interface to Driver Station New feature: practice timer with audio cues New feature (Control Hub only): wireless network connection strength indicator (0-5 bars) New feature (Control Hub only): tapping on the ping/channel display will switch to an alternate display showing radio RX dBm and link speed (tap again to switch back) The layout will NOT autorotate. You can switch the layout from the Driver Station's settings menu. Breaking changes Removes support for Android versions 4.4 through 5.1 (KitKat and Lollipop). The minSdkVersion is now 23. Removes the deprecated LinearOpMode methods waitOneFullHardwareCycle() and waitForNextHardwareCycle() Enhancements Handles RS485 address of Control Hub automatically The Control Hub is automatically given a reserved address Existing configuration files will continue to work All addresses in the range of 1-10 are still available for Expansion Hubs The Control Hub light will now normally be solid green, without blinking to indicate the address The Control Hub will not be shown on the Expansion Hub Address Change settings page Improves REV Hub firmware updater The user can now choose between all available firmware update files Version 1.8.2 of the REV Hub firmware is bundled into the Robot Controller app. Text was added to clarify that Expansion Hubs can only be updated via USB. Firmware update speed was reduced to improve reliability Allows REV Hub firmware to be updated directly from the Manage webpage Improves log viewer on Robot Controller Horizontal scrolling support (no longer word wrapped) Supports pinch-to-zoom Uses a monospaced font Error messages are highlighted New color scheme Attempts to force-stop a runaway/stuck OpMode without restarting the entire app Not all types of runaway conditions are stoppable, but if the user code attempts to talk to hardware during the runaway, the system should be able to capture it. Makes various tweaks to the Self Inspect screen Renames "OS version" entry to "Android version" Renames "WiFi Direct Name" to "WiFi Name" Adds Control Hub OS version, when viewing the report of a Control Hub Hides the airplane mode entry, when viewing the report of a Control Hub Removes check for ZTE Speed Channel Changer Shows firmware version for all Expansion and Control Hubs Reworks network settings portion of Manage page All network settings are now applied with a single click The WiFi Direct channel of phone-based Robot Controllers can now be changed from the Manage page WiFi channels are filtered by band (2.4 vs 5 GHz) and whether they overlap with other channels The current WiFi channel is pre-selected on phone-based Robot Controllers, and Control Hubs running OS 1.1.2 or later. On Control Hubs running OS 1.1.2 or later, you can choose to have the system automatically select a channel on the 5 GHz band Improves OnBotJava New light and dark themes replace the old themes (chaos, github, chrome,...) the new default theme is light and will be used when you first update to this version OnBotJava now has a tabbed editor Read-only offline mode Improves function of "exit" menu item on Robot Controller and Driver Station Now guaranteed to be fully stopped and unloaded from memory Shows a warning message if a LinearOpMode exists prematurely due to failure to monitor for the start condition Improves error message shown when the Driver Station and Robot Controller are incompatible with each other Driver Station OpMode Control Panel now disabled while a Restart Robot is in progress Disables advanced settings related to WiFi direct when the Robot Controller is a Control Hub. Tint phone battery icons on Driver Station when low/critical. Uses names "Control Hub Portal" and "Control Hub" (when appropriate) in new configuration files Improve I2C read performance Very large improvement on Control Hub; up to ~2x faster with small (e.g. 6 byte) reads Not as apparent on Expansion Hubs connected to a phone Update/refresh build infrastructure Update to 'androidx' support library from 'com.android.support:appcompat', which is end-of-life Update targetSdkVersion and compileSdkVersion to 28 Update Android Studio's Android plugin to latest Fix reported build timestamp in 'About' screen Add sample illustrating manual webcam use: ConceptWebcam Bug fixes Fixes SkyStone issue #248 Fixes SkyStone issue #232 and modifies bulk caching semantics to allow for cache-preserving MANUAL/AUTO transitions. Improves performance when REV 2M distance sensor is unplugged Improves readability of Toast messages on certain devices Allows a Driver Station to connect to a Robot Controller after another has disconnected Improves generation of fake serial numbers for UVC cameras which do not provide a real serial number Previously some devices would assign such cameras a serial of 0:0 and fail to open and start streaming Fixes ftc_app issue #638. Fixes a slew of bugs with the Vuforia camera monitor including: Fixes bug where preview could be displayed with a wonky aspect ratio Fixes bug where preview could be cut off in landscape Fixes bug where preview got totally messed up when rotating phone Fixes bug where crosshair could drift off target when using webcams Fixes issue in UVC driver on some devices (ftc_app 681) if streaming was started/stopped multiple times in a row Issue manifested as kernel panic on devices which do not have this kernel patch. On affected devices which do have the patch, the issue was manifest as simply a failure to start streaming. The Tech Team believes that the root cause of the issue is a bug in the Linux kernel XHCI driver. A workaround was implemented in the SDK UVC driver. Fixes bug in UVC driver where often half the frames from the camera would be dropped (e.g. only 15FPS delivered during a streaming session configured for 30FPS). Fixes issue where TensorFlow Object Detection would show results whose confidence was lower than the minimum confidence parameter. Fixes a potential exploitation issue of CVE-2019-11358 in OnBotJava Fixes changing the address of an Expansion Hub with additional Expansion Hubs connected to it Preserves the Control Hub's network connection when "Restart Robot" is selected Fixes issue where device scans would fail while the Robot was restarting Fix RenderScript usage Use androidx.renderscript variant: increased compatibility Use RenderScript in Java mode, not native: simplifies build Fixes webcam-frame-to-bitmap conversion problem: alpha channel wasn't being initialized, only R, G, & B Fixes possible arithmetic overflow in Deadline Fixes deadlock in Vuforia webcam support which could cause 5-second delays when stopping OpMode Version 5.4 (20200108-101156) Fixes SkyStone issue #88 Adds an inspection item that notes when a robot controller (Control Hub) is using the factory default password. Fixes SkyStone issue #61 Fixes SkyStone issue #142 Fixes ftc_app issue #417 by adding more current and voltage monitoring capabilities for REV Hubs. Fixes a crash sometimes caused by OnBotJava activity Improves OnBotJava autosave functionality ftc_app #738 Fixes system responsiveness issue when an Expansion Hub is disconnected Fixes issue where IMU initialization could prevent Op Modes from stopping Fixes issue where AndroidTextToSpeech.speak() would fail if it was called too early Adds telemetry.speak() methods and blocks, which cause the Driver Station (if also updated) to speak text Adds and improves Expansion Hub-related warnings Improves Expansion Hub low battery warning Displays the warning immediately after the hub reports it Specifies whether the condition is current or occurred temporarily during an OpMode run Displays which hubs reported low battery Displays warning when hub loses and regains power during an OpMode run Fixes the hub's LED pattern after this condition Displays warning when Expansion Hub is not responding to commands Specifies whether the condition is current or occurred temporarily during an OpMode run Clarifies warning when Expansion Hub is not present at startup Specifies that this condition requires a Robot Restart before the hub can be used. The hub light will now accurately reflect this state Improves logging and reduces log spam during these conditions Syncs the Control Hub time and timezone to a connected web browser programming the robot, if a Driver Station is not available. Adds bulk read functionality for REV Hubs A bulk caching mode must be set at the Hub level with LynxModule#setBulkCachingMode(). This applies to all relevant SDK hardware classes that reference that Hub. The following following Hub bulk caching modes are available: BulkCachingMode.OFF (default): All hardware calls operate as usual. Bulk data can read through LynxModule#getBulkData() and processed manually. BulkCachingMode.AUTO: Applicable hardware calls are served from a bulk read cache that is cleared/refreshed automatically to ensure identical commands don't hit the same cache. The cache can also be cleared manually with LynxModule#clearBulkCache(), although this is not recommended. (advanced users) BulkCachingMode.MANUAL: Same as BulkCachingMode.AUTO except the cache is never cleared automatically. To avoid getting stale data, the cache must be manually cleared at the beginning of each loop body or as the user deems appropriate. Removes PIDF Annotation values added in Rev 5.3 (to AndyMark, goBILDA and TETRIX motor configurations). The new motor types will still be available but their Default control behavior will revert back to Rev 5.2 Adds new ConceptMotorBulkRead sample Opmode to demonstrate and compare Motor Bulk-Read modes for reducing I/O latencies. Version 5.3 (20191004-112306) Fixes external USB/UVC webcam support Makes various bugfixes and improvements to Blocks page, including but not limited to: Many visual tweaks Browser zoom and window resize behave better Resizing the Java preview pane works better and more consistently across browsers The Java preview pane consistently gets scrollbars when needed The Java preview pane is hidden by default on phones Internet Explorer 11 should work Large dropdown lists display properly on lower res screens Disabled buttons are now visually identifiable as disabled A warning is shown if a user selects a TFOD sample, but their device is not compatible Warning messages in a Blocks op mode are now visible by default. Adds goBILDA 5201 and 5202 motors to Robot Configurator Adds PIDF Annotation values to AndyMark, goBILDA and TETRIX motor configurations. This has the effect of causing the RUN_USING_ENCODERS and RUN_TO_POSITION modes to use PIDF vs PID closed loop control on these motors. This should provide more responsive, yet stable, speed control. PIDF adds Feedforward control to the basic PID control loop. Feedforward is useful when controlling a motor's speed because it "anticipates" how much the control voltage must change to achieve a new speed set-point, rather than requiring the integrated error to change sufficiently. The PIDF values were chosen to provide responsive, yet stable, speed control on a lightly loaded motor. The more heavily a motor is loaded (drag or friction), the more noticable the PIDF improvement will be. Fixes startup crash on Android 10 Fixes ftc_app issue #712 (thanks to FROGbots-4634) Fixes ftc_app issue #542 Allows "A" and lowercase letters when naming device through RC and DS apps. Version 5.2 (20190905-083277) Fixes extra-wide margins on settings activities, and placement of the new configuration button Adds Skystone Vuforia image target data. Includes sample Skystone Vuforia Navigation op modes (Java). Includes sample Skystone Vuforia Navigation op modes (Blocks). Adds TensorFlow inference model (.tflite) for Skystone game elements. Includes sample Skystone TensorFlow op modes (Java). Includes sample Skystone TensorFlow op modes (Blocks). Removes older (season-specific) sample op modes. Includes 64-bit support (to comply with Google Play requirements). Protects against Stuck OpModes when a Restart Robot is requested. (Thanks to FROGbots-4634) (ftc_app issue #709) Blocks related changes: Fixes bug with blocks generated code when hardware device name is a java or javascript reserved word. Shows generated java code for blocks, even when hardware items are missing from the active configuration. Displays warning icon when outdated Vuforia and TensorFlow blocks are used (SkyStone issue #27) Version 5.1 (20190820-222104) Defines default PIDF parameters for the following motors: REV Core Hex Motor REV 20:1 HD Hex Motor REV 40:1 HD Hex Motor Adds back button when running on a device without a system back button (such as a Control Hub) Allows a REV Control Hub to update the firmware on a REV Expansion Hub via USB Fixes SkyStone issue #9 Fixes ftc_app issue #715 Prevents extra DS User clicks by filtering based on current state. Prevents incorrect DS UI state changes when receiving new OpMode list from RC Adds support for REV Color Sensor V3 Adds a manual-refresh DS Camera Stream for remotely viewing RC camera frames. To show the stream on the DS, initialize but do not run a stream-enabled opmode, select the Camera Stream option in the DS menu, and tap the image to refresh. This feature is automatically enabled when using Vuforia or TFOD—no additional RC configuration is required for typical use cases. To hide the stream, select the same menu item again. Note that gamepads are disabled and the selected opmode cannot be started while the stream is open as a safety precaution. To use custom streams, consult the API docs for CameraStreamServer#setSource and CameraStreamSource. Adds many Star Wars sounds to RobotController resources. Added SKYSTONE Sounds Chooser Sample Program. Switches out startup, connect chimes, and error/warning sounds for Star Wars sounds Updates OnBot Java to use a WebSocket for communication with the robot The OnBot Java page no longer has to do a full refresh when a user switches from editing one file to another Known issues: Camera Stream The Vuforia camera stream inherits the issues present in the phone preview (namely ftc_app issue #574). This problem does not affect the TFOD camera stream even though it receives frames from Vuforia. The orientation of the stream frames may not always match the phone preview. For now, these frames may be rotated manually via a custom CameraStreamSource if desired. OnBotJava Browser back button may not always work correctly It's possible for a build to be queued, but not started. The OnBot Java build console will display a warning if this occurs. A user might not realize they are editing a different file if the user inadvertently switches from one file to another since this switch is now seamless. The name of the currently open file is displayed in the browser tab. Version 5.0 (built on 19.06.14) Support for the REV Robotics Control Hub. Adds a Java preview pane to the Blocks editor. Adds a new offline export feature to the Blocks editor. Display wifi channel in Network circle on Driver Station. Adds calibration for Logitech C270 Updates build tooling and target SDK. Compliance with Google's permissions infrastructure (Required after build tooling update). Keep Alives to mitigate the Motorola wifi scanning problem. Telemetry substitute no longer necessary. Improves Vuforia error reporting. Fixes ftctechnh/ftc_app issues 621, 713. Miscellaneous bug fixes and improvements. Version 4.3 (built on 18.10.31) Includes missing TensorFlow-related libraries and files. Version 4.2 (built on 18.10.30) Includes fix to avoid deadlock situation with WatchdogMonitor which could result in USB communication errors. Comm error appeared to require that user disconnect USB cable and restart the Robot Controller app to recover. robotControllerLog.txt would have error messages that included the words "E RobotCore: lynx xmit lock: #### abandoning lock:" Includes fix to correctly list the parent module address for a REV Robotics Expansion Hub in a configuration (.xml) file. Bug in versions 4.0 and 4.1 would incorrect list the address module for a parent REV Robotics device as "1". If the parent module had a higher address value than the daisy-chained module, then this bug would prevent the Robot Controller from communicating with the downstream Expansion Hub. Added requirement for ACCESS_COARSE_LOCATION to allow a Driver Station running Android Oreo to scan for Wi-Fi Direct devices. Added google() repo to build.gradle because aapt2 must be downloaded from the google() repository beginning with version 3.2 of the Android Gradle Plugin. Important Note: Android Studio users will need to be connected to the Internet the first time build the ftc_app project. Internet connectivity is required for the first build so the appropriate files can be downloaded from the Google repository. Users should not need to be connected to the Internet for subsequent builds. This should also fix buid issue where Android Studio would complain that it "Could not find com.android.tools.lint:lint-gradle:26.1.4" (or similar). Added support for REV Spark Mini motor controller as part of the configuration menu for a servo/PWM port on the REV Expansion Hub. Provide examples for playing audio files in an Op Mode. Block Development Tool Changes Includes a fix for a problem with the Velocity blocks that were reported in the FTC Technology forum (Blocks Programming subforum). Change the "Save completed successfully." message to a white color so it will contrast with a green background. Fixed the "Download image" feature so it will work if there are text blocks in the op mode. Introduce support for Google's TensorFlow Lite technology for object detetion for 2018-2019 game. TensorFlow lite can recognize Gold Mineral and Silver Mineral from 2018-2019 game. Example Java and Block op modes are included to show how to determine the relative position of the gold block (left, center, right). Version 4.1 (released on 18.09.24) Changes include: Fix to prevent crash when deprecated configuration annotations are used. Change to allow FTC Robot Controller APK to be auto-updated using FIRST Global Control Hub update scripts. Removed samples for non supported / non legal hardware. Improvements to Telemetry.addData block with "text" socket. Updated Blocks sample op mode list to include Rover Ruckus Vuforia example. Update SDK library version number. Version 4.0 (released on 18.09.12) Changes include: Initial support for UVC compatible cameras If UVC camera has a unique serial number, RC will detect and enumerate by serial number. If UVC camera lacks a unique serial number, RC will only support one camera of that type connected. Calibration settings for a few cameras are included (see TeamCode/src/main/res/xml/teamwebcamcalibrations.xml for details). User can upload calibration files from Program and Manage web interface. UVC cameras seem to draw a fair amount of electrical current from the USB bus. This does not appear to present any problems for the REV Robotics Control Hub. This does seem to create stability problems when using some cameras with an Android phone-based Robot Controller. FTC Tech Team is investigating options to mitigate this issue with the phone-based Robot Controllers. Updated sample Vuforia Navigation and VuMark Op Modes to demonstrate how to use an internal phone-based camera and an external UVC webcam. Support for improved motor control. REV Robotics Expansion Hub firmware 1.8 and greater will support a feed forward mechanism for closed loop motor control. FTC SDK has been modified to support PIDF coefficients (proportional, integral, derivative, and feed forward). FTC Blocks development tool modified to include PIDF programming blocks. Deprecated older PID-related methods and variables. REV's 1.8.x PIDF-related changes provide a more linear and accurate way to control a motor. Wireless Added 5GHz support for wireless channel changing for those devices that support it. Tested with Moto G5 and E4 phones. Also tested with other (currently non-approved) phones such as Samsung Galaxy S8. Improved Expansion Hub firmware update support in Robot Controller app Changes to make the system more robust during the firmware update process (when performed through Robot Controller app). User no longer has to disconnect a downstream daisy-chained Expansion Hub when updating an Expansion Hub's firmware. If user is updating an Expansion Hub's firmware through a USB connection, he/she does not have to disconnect RS485 connection to other Expansion Hubs. The user still must use a USB connection to update an Expansion Hub's firmware. The user cannot update the Expansion Hub firmware for a downstream device that is daisy chained through an RS485 connection. If an Expansion Hub accidentally gets "bricked" the Robot Controller app is now more likely to recognize the Hub when it scans the USB bus. Robot Controller app should be able to detect an Expansion Hub, even if it accidentally was bricked in a previous update attempt. Robot Controller app should be able to install the firmware onto the Hub, even if if accidentally was bricked in a previous update attempt. Resiliency FTC software can detect and enable an FTDI reset feature that is available with REV Robotics v1.8 Expansion Hub firmware and greater. When enabled, the Expansion Hub can detect if it hasn't communicated with the Robot Controller over the FTDI (USB) connection. If the Hub hasn't heard from the Robot Controller in a while, it will reset the FTDI connection. This action helps system recover from some ESD-induced disruptions. Various fixes to improve reliability of FTC software. Blocks Fixed errors with string and list indices in blocks export to java. Support for USB connected UVC webcams. Refactored optimized Blocks Vuforia code to support Rover Ruckus image targets. Added programming blocks to support PIDF (proportional, integral, derivative and feed forward) motor control. Added formatting options (under Telemetry and Miscellaneous categories) so user can set how many decimal places to display a numerical value. Support to play audio files (which are uploaded through Blocks web interface) on Driver Station in addition to the Robot Controller. Fixed bug with Download Image of Blocks feature. Support for REV Robotics Blinkin LED Controller. Support for REV Robotics 2m Distance Sensor. Added support for a REV Touch Sensor (no longer have to configure as a generic digital device). Added blocks for DcMotorEx methods. These are enhanced methods that you can use when supported by the motor controller hardware. The REV Robotics Expansion Hub supports these enhanced methods. Enhanced methods include methods to get/set motor velocity (in encoder pulses per second), get/set PIDF coefficients, etc.. Modest Improvements in Logging Decrease frequency of battery checker voltage statements. Removed non-FTC related log statements (wherever possible). Introduced a "Match Logging" feature. Under "Settings" a user can enable/disable this feature (it's disabled by default). If enabled, user provides a "Match Number" through the Driver Station user interface (top of the screen). The Match Number is used to create a log file specifically with log statements from that particular Op Mode run. Match log files are stored in /sdcard/FIRST/matlogs on the Robot Controller. Once an op mode run is complete, the Match Number is cleared. This is a convenient way to create a separate match log with statements only related to a specific op mode run. New Devices Support for REV Robotics Blinkin LED Controller. Support for REV Robotics 2m Distance Sensor. Added configuration option for REV 20:1 HD Hex Motor. Added support for a REV Touch Sensor (no longer have to configure as a generic digital device). Miscellaneous Fixed some errors in the definitions for acceleration and velocity in our javadoc documentation. Added ability to play audio files on Driver Station When user is configuring an Expansion Hub, the LED on the Expansion Hub will change blink pattern (purple-cyan) to indicate which Hub is currently being configured. Renamed I2cSensorType to I2cDeviceType. Added an external sample Op Mode that demonstrates localization using 2018-2019 (Rover Ruckus presented by QualComm) Vuforia targets. Added an external sample Op Mode that demonstrates how to use the REV Robotics 2m Laser Distance Sensor. Added an external sample Op Mode that demonstrates how to use the REV Robotics Blinkin LED Controller. Re-categorized external Java sample Op Modes to "TeleOp" instead of "Autonomous". Known issues: Initial support for UVC compatible cameras UVC cameras seem to draw significant amount of current from the USB bus. This does not appear to present any problems for the REV Robotics Control Hub. This does seem to create stability problems when using some cameras with an Android phone-based Robot Controller. FTC Tech Team is investigating options to mitigate this issue with the phone-based Robot Controllers. There might be a possible deadlock which causes the RC to become unresponsive when using a UVC webcam with a Nougat Android Robot Controller. Wireless When user selects a wireless channel, this channel does not necessarily persist if the phone is power cycled. Tech Team is hoping to eventually address this issue in a future release. Issue has been present since apps were introduced (i.e., it is not new with the v4.0 release). Wireless channel is not currently displayed for WiFi Direct connections. Miscellaneous The blink indication feature that shows which Expansion Hub is currently being configured does not work for a newly created configuration file. User has to first save a newly created configuration file and then close and re-edit the file in order for blink indicator to work. Version 3.6 (built on 17.12.18) Changes include: Blocks Changes Uses updated Google Blockly software to allow users to edit their op modes on Apple iOS devices (including iPad and iPhone). Improvement in Blocks tool to handle corrupt op mode files. Autonomous op modes should no longer get switched back to tele-op after re-opening them to be edited. The system can now detect type mismatches during runtime and alert the user with a message on the Driver Station. Updated javadoc documentation for setPower() method to reflect correct range of values (-1 to +1). Modified VuforiaLocalizerImpl to allow for user rendering of frames Added a user-overrideable onRenderFrame() method which gets called by the class's renderFrame() method. Version 3.5 (built on 17.10.30) Changes with version 3.5 include: Introduced a fix to prevent random op mode stops, which can occur after the Robot Controller app has been paused and then resumed (for example, when a user temporarily turns off the display of the Robot Controller phone, and then turns the screen back on). Introduced a fix to prevent random op mode stops, which were previously caused by random peer disconnect events on the Driver Station. Fixes issue where log files would be closed on pause of the RC or DS, but not re-opened upon resume. Fixes issue with battery handler (voltage) start/stop race. Fixes issue where Android Studio generated op modes would disappear from available list in certain situations. Fixes problem where OnBot Java would not build on REV Robotics Control Hub. Fixes problem where OnBot Java would not build if the date and time on the Robot Controller device was "rewound" (set to an earlier date/time). Improved error message on OnBot Java that occurs when renaming a file fails. Removed unneeded resources from android.jar binaries used by OnBot Java to reduce final size of Robot Controller app. Added MR_ANALOG_TOUCH_SENSOR block to Blocks Programming Tool. Version 3.4 (built on 17.09.06) Changes with version 3.4 include: Added telemetry.update() statement for BlankLinearOpMode template. Renamed sample Block op modes to be more consistent with Java samples. Added some additional sample Block op modes. Reworded OnBot Java readme slightly. Version 3.3 (built on 17.09.04) This version of the software includes improves for the FTC Blocks Programming Tool and the OnBot Java Programming Tool. Changes with verion 3.3 include: Android Studio ftc_app project has been updated to use Gradle Plugin 2.3.3. Android Studio ftc_app project is already using gradle 3.5 distribution. Robot Controller log has been renamed to /sdcard/RobotControllerLog.txt (note that this change was actually introduced w/ v3.2). Improvements in I2C reliability. Optimized I2C read for REV Expansion Hub, with v1.7 firmware or greater. Updated all external/samples (available through OnBot and in Android project folder). Vuforia Added support for VuMarks that will be used for the 2017-2018 season game. Blocks Update to latest Google Blockly release. Sample op modes can be selected as a template when creating new op mode. Fixed bug where the blocks would disappear temporarily when mouse button is held down. Added blocks for Range.clip and Range.scale. User can now disable/enable Block op modes. Fix to prevent occasional Blocks deadlock. OnBot Java Significant improvements with autocomplete function for OnBot Java editor. Sample op modes can be selected as a template when creating new op mode. Fixes and changes to complete hardware setup feature. Updated (and more useful) onBot welcome message. Known issues: Android Studio After updating to the new v3.3 Android Studio project folder, if you get error messages indicating "InvalidVirtualFileAccessException" then you might need to do a File->Invalidate Caches / Restart to clear the error. OnBot Java Sometimes when you push the build button to build all op modes, the RC returns an error message that the build failed. If you press the build button a second time, the build typically suceeds. Version 3.2 (built on 17.08.02) This version of the software introduces the "OnBot Java" Development Tool. Similar to the FTC Blocks Development Tool, the FTC OnBot Java Development Tool allows a user to create, edit and build op modes dynamically using only a Javascript-enabled web browser. The OnBot Java Development Tool is an integrated development environment (IDE) that is served up by the Robot Controller. Op modes are created and edited using a Javascript-enabled browser (Google Chromse is recommended). Op modes are saved on the Robot Controller Android device directly. The OnBot Java Development Tool provides a Java programming environment that does NOT need Android Studio. Changes with version 3.2 include: Enhanced web-based development tools Introduction of OnBot Java Development Tool. Web-based programming and management features are "always on" (user no longer needs to put Robot Controller into programming mode). Web-based management interface (where user can change Robot Controller name and also easily download Robot Controller log file). OnBot Java, Blocks and Management features available from web based interface. Blocks Programming Development Tool: Changed "LynxI2cColorRangeSensor" block to "REV Color/range sensor" block. Fixed tooltip for ColorSensor.isLightOn block. Added blocks for ColorSensor.getNormalizedColors and LynxI2cColorRangeSensor.getNormalizedColors. Added example op modes for digital touch sensor and REV Robotics Color Distance sensor. User selectable color themes. Includes many minor enhancements and fixes (too numerous to list). Known issues: Auto complete function is incomplete and does not support the following (for now): Access via this keyword Access via super keyword Members of the super cloass, not overridden by the class Any methods provided in the current class Inner classes Can't handle casted objects Any objects coming from an parenthetically enclosed expression Version 3.10 (built on 17.05.09) This version of the software provides support for the REV Robotics Expansion Hub. This version also includes improvements in the USB communication layer in an effort to enhance system resiliency. If you were using a 2.x version of the software previously, updating to version 3.1 requires that you also update your Driver Station software in addition to updating the Robot Controller software. Also note that in version 3.10 software, the setMaxSpeed and getMaxSpeed methods are no longer available (not deprecated, they have been removed from the SDK). Also note that the the new 3.x software incorporates motor profiles that a user can select as he/she configures the robot. Changes include: Blocks changes Added VuforiaTrackableDefaultListener.getPose and Vuforia.trackPose blocks. Added optimized blocks support for Vuforia extended tracking. Added atan2 block to the math category. Added useCompetitionFieldTargetLocations parameter to Vuforia.initialize block. If set to false, the target locations are placed at (0,0,0) with target orientation as specified in https://github.com/gearsincorg/FTCVuforiaDemo/blob/master/Robot_Navigation.java tutorial op mode. Incorporates additional improvements to USB comm layer to improve system resiliency (to recover from a greater number of communication disruptions). Additional Notes Regarding Version 3.00 (built on 17.04.13) In addition to the release changes listed below (see section labeled "Version 3.00 (built on 17.04.013)"), version 3.00 has the following important changes: Version 3.00 software uses a new version of the FTC Robocol (robot protocol). If you upgrade to v3.0 on the Robot Controller and/or Android Studio side, you must also upgrade the Driver Station software to match the new Robocol. Version 3.00 software removes the setMaxSpeed and getMaxSpeed methods from the DcMotor class. If you have an op mode that formerly used these methods, you will need to remove the references/calls to these methods. Instead, v3.0 provides the max speed information through the use of motor profiles that are selected by the user during robot configuration. Version 3.00 software currently does not have a mechanism to disable extra i2c sensors. We hope to re-introduce this function with a release in the near future. Version 3.00 (built on 17.04.13) *** Use this version of the software at YOUR OWN RISK!!! *** This software is being released as an "alpha" version. Use this version at your own risk! This pre-release software contains SIGNIFICANT changes, including changes to the Wi-Fi Direct pairing mechanism, rewrites of the I2C sensor classes, changes to the USB/FTDI layer, and the introduction of support for the REV Robotics Expansion Hub and the REV Robotics color-range-light sensor. These changes were implemented to improve the reliability and resiliency of the FTC control system. Please note, however, that version 3.00 is considered "alpha" code. This code is being released so that the FIRST community will have an opportunity to test the new REV Expansion Hub electronics module when it becomes available in May. The developers do not recommend using this code for critical applications (i.e., competition use). *** Use this version of the software at YOUR OWN RISK!!! *** Changes include: Major rework of sensor-related infrastructure. Includes rewriting sensor classes to implement synchronous I2C communication. Fix to reset Autonomous timer back to 30 seconds. Implementation of specific motor profiles for approved 12V motors (includes Tetrix, AndyMark, Matrix and REV models). Modest improvements to enhance Wi-Fi P2P pairing. Fixes telemetry log addition race. Publishes all the sources (not just a select few). Includes Block programming improvements Addition of optimized Vuforia blocks. Auto scrollbar to projects and sounds pages. Fixed blocks paste bug. Blocks execute after while-opModeIsActive loop (to allow for cleanup before exiting op mode). Added gyro integratedZValue block. Fixes bug with projects page for Firefox browser. Added IsSpeaking block to AndroidTextToSpeech. Implements support for the REV Robotics Expansion Hub Implements support for integral REV IMU (physically installed on I2C bus 0, uses same Bosch BNO055 9 axis absolute orientation sensor as Adafruit 9DOF abs orientation sensor). - Implements support for REV color/range/light sensor. Provides support to update Expansion Hub firmware through FTC SDK. Detects REV firmware version and records in log file. Includes support for REV Control Hub (note that the REV Control Hub is not yet approved for FTC use). Implements FTC Blocks programming support for REV Expansion Hub and sensor hardware. Detects and alerts when I2C device disconnect. Version 2.62 (built on 17.01.07) Added null pointer check before calling modeToByte() in finishModeSwitchIfNecessary method for ModernRoboticsUsbDcMotorController class. Changes to enhance Modern Robotics USB protocol robustness. Version 2.61 (released on 16.12.19) Blocks Programming mode changes: Fix to correct issue when an exception was thrown because an OpticalDistanceSensor object appears twice in the hardware map (the second time as a LightSensor). Version 2.6 (released on 16.12.16) Fixes for Gyro class: Improve (decrease) sensor refresh latency. fix isCalibrating issues. Blocks Programming mode changes: Blocks now ignores a device in the configuration xml if the name is empty. Other devices work in configuration work fine. Version 2.5 (internal release on released on 16.12.13) Blocks Programming mode changes: Added blocks support for AdafruitBNO055IMU. Added Download Op Mode button to FtcBocks.html. Added support for copying blocks in one OpMode and pasting them in an other OpMode. The clipboard content is stored on the phone, so the programming mode server must be running. Modified Utilities section of the toolbox. In Programming Mode, display information about the active connections. Fixed paste location when workspace has been scrolled. Added blocks support for the android Accelerometer. Fixed issue where Blocks Upload Op Mode truncated name at first dot. Added blocks support for Android SoundPool. Added type safety to blocks for Acceleration. Added type safety to blocks for AdafruitBNO055IMU.Parameters. Added type safety to blocks for AnalogInput. Added type safety to blocks for AngularVelocity. Added type safety to blocks for Color. Added type safety to blocks for ColorSensor. Added type safety to blocks for CompassSensor. Added type safety to blocks for CRServo. Added type safety to blocks for DigitalChannel. Added type safety to blocks for ElapsedTime. Added type safety to blocks for Gamepad. Added type safety to blocks for GyroSensor. Added type safety to blocks for IrSeekerSensor. Added type safety to blocks for LED. Added type safety to blocks for LightSensor. Added type safety to blocks for LinearOpMode. Added type safety to blocks for MagneticFlux. Added type safety to blocks for MatrixF. Added type safety to blocks for MrI2cCompassSensor. Added type safety to blocks for MrI2cRangeSensor. Added type safety to blocks for OpticalDistanceSensor. Added type safety to blocks for Orientation. Added type safety to blocks for Position. Added type safety to blocks for Quaternion. Added type safety to blocks for Servo. Added type safety to blocks for ServoController. Added type safety to blocks for Telemetry. Added type safety to blocks for Temperature. Added type safety to blocks for TouchSensor. Added type safety to blocks for UltrasonicSensor. Added type safety to blocks for VectorF. Added type safety to blocks for Velocity. Added type safety to blocks for VoltageSensor. Added type safety to blocks for VuforiaLocalizer.Parameters. Added type safety to blocks for VuforiaTrackable. Added type safety to blocks for VuforiaTrackables. Added type safety to blocks for enums in AdafruitBNO055IMU.Parameters. Added type safety to blocks for AndroidAccelerometer, AndroidGyroscope, AndroidOrientation, and AndroidTextToSpeech. Version 2.4 (released on 16.11.13) Fix to avoid crashing for nonexistent resources. Blocks Programming mode changes: Added blocks to support OpenGLMatrix, MatrixF, and VectorF. Added blocks to support AngleUnit, AxesOrder, AxesReference, CameraDirection, CameraMonitorFeedback, DistanceUnit, and TempUnit. Added blocks to support Acceleration. Added blocks to support LinearOpMode.getRuntime. Added blocks to support MagneticFlux and Position. Fixed typos. Made blocks for ElapsedTime more consistent with other objects. Added blocks to support Quaternion, Velocity, Orientation, AngularVelocity. Added blocks to support VuforiaTrackables, VuforiaTrackable, VuforiaLocalizer, VuforiaTrackableDefaultListener. Fixed a few blocks. Added type checking to new blocks. Updated to latest blockly. Added default variable blocks to navigation and matrix blocks. Fixed toolbox entry for openGLMatrix_rotation_withAxesArgs. When user downloads Blocks-generated op mode, only the .blk file is downloaded. When user uploads Blocks-generated op mode (.blk file), Javascript code is auto generated. Added DbgLog support. Added logging when a blocks file is read/written. Fixed bug to properly render blocks even if missing devices from configuration file. Added support for additional characters (not just alphanumeric) for the block file names (for download and upload). Added support for OpMode flavor (“Autonomous” or “TeleOp”) and group. Changes to Samples to prevent tutorial issues. Incorporated suggested changes from public pull 216 (“Replace .. paths”). Remove Servo Glitches when robot stopped. if user hits “Cancels” when editing a configuration file, clears the unsaved changes and reverts to original unmodified configuration. Added log info to help diagnose why the Robot Controller app was terminated (for example, by watch dog function). Added ability to transfer log from the controller. Fixed inconsistency for AngularVelocity Limit unbounded growth of data for telemetry. If user does not call telemetry.update() for LinearOpMode in a timely manner, data added for telemetry might get lost if size limit is exceeded. Version 2.35 (released on 16.10.06) Blockly programming mode - Removed unnecesary idle() call from blocks for new project. Version 2.30 (released on 16.10.05) Blockly programming mode: Mechanism added to save Blockly op modes from Programming Mode Server onto local device To avoid clutter, blocks are displayed in categorized folders Added support for DigitalChannel Added support for ModernRoboticsI2cCompassSensor Added support for ModernRoboticsI2cRangeSensor Added support for VoltageSensor Added support for AnalogInput Added support for AnalogOutput Fix for CompassSensor setMode block Vuforia Fix deadlock / make camera data available while Vuforia is running. Update to Vuforia 6.0.117 (recommended by Vuforia and Google to close security loophole). Fix for autonomous 30 second timer bug (where timer was in effect, even though it appeared to have timed out). opModeIsActive changes to allow cleanup after op mode is stopped (with enforced 2 second safety timeout). Fix to avoid reading i2c twice. Updated sample Op Modes. Improved logging and fixed intermittent freezing. Added digital I/O sample. Cleaned up device names in sample op modes to be consistent with Pushbot guide. Fix to allow use of IrSeekerSensorV3. Version 2.20 (released on 16.09.08) Support for Modern Robotics Compass Sensor. Support for Modern Robotics Range Sensor. Revise device names for Pushbot templates to match the names used in Pushbot guide. Fixed bug so that IrSeekerSensorV3 device is accessible as IrSeekerSensor in hardwareMap. Modified computer vision code to require an individual Vuforia license (per legal requirement from PTC). Minor fixes. Blockly enhancements: Support for Voltage Sensor. Support for Analog Input. Support for Analog Output. Support for Light Sensor. Support for Servo Controller. Version 2.10 (released on 16.09.03) Support for Adafruit IMU. Improvements to ModernRoboticsI2cGyro class Block on reset of z axis. isCalibrating() returns true while gyro is calibration. Updated sample gyro program. Blockly enhancements support for android.graphics.Color. added support for ElapsedTime. improved look and legibility of blocks. support for compass sensor. support for ultrasonic sensor. support for IrSeeker. support for LED. support for color sensor. support for CRServo prompt user to configure robot before using programming mode. Provides ability to disable audio cues. various bug fixes and improvements. Version 2.00 (released on 16.08.19) This is the new release for the upcoming 2016-2017 FIRST Tech Challenge Season. Channel change is enabled in the FTC Robot Controller app for Moto G 2nd and 3rd Gen phones. Users can now use annotations to register/disable their Op Modes. Changes in the Android SDK, JDK and build tool requirements (minsdk=19, java 1.7, build tools 23.0.3). Standardized units in analog input. Cleaned up code for existing analog sensor classes. setChannelMode and getChannelMode were REMOVED from the DcMotorController class. This is important - we no longer set the motor modes through the motor controller. setMode and getMode were added to the DcMotor class. ContinuousRotationServo class has been added to the FTC SDK. Range.clip() method has been overloaded so it can support this operation for int, short and byte integers. Some changes have been made (new methods added) on how a user can access items from the hardware map. Users can now set the zero power behavior for a DC motor so that the motor will brake or float when power is zero. Prototype Blockly Programming Mode has been added to FTC Robot Controller. Users can place the Robot Controller into this mode, and then use a device (such as a laptop) that has a Javascript enabled browser to write Blockly-based Op Modes directly onto the Robot Controller. Users can now configure the robot remotely through the FTC Driver Station app. Android Studio project supports Android Studio 2.1.x and compile SDK Version 23 (Marshmallow). Vuforia Computer Vision SDK integrated into FTC SDK. Users can use sample vision targets to get localization information on a standard FTC field. Project structure has been reorganized so that there is now a TeamCode package that users can use to place their local/custom Op Modes into this package. Inspection function has been integrated into the FTC Robot Controller and Driver Station Apps (Thanks Team HazMat… 9277 & 10650!). Audio cues have been incorporated into FTC SDK. Swap mechanism added to FTC Robot Controller configuration activity. For example, if you have two motor controllers on a robot, and you misidentified them in your configuration file, you can use the Swap button to swap the devices within the configuration file (so you do not have to manually re-enter in the configuration info for the two devices). Fix mechanism added to all user to replace an electronic module easily. For example, suppose a servo controller dies on your robot. You replace the broken module with a new module, which has a different serial number from the original servo controller. You can use the Fix button to automatically reconfigure your configuration file to use the serial number of the new module. Improvements made to fix resiliency and responsiveness of the system. For LinearOpMode the user now must for a telemetry.update() to update the telemetry data on the driver station. This update() mechanism ensures that the driver station gets the updated data properly and at the same time. The Auto Configure function of the Robot Controller is now template based. If there is a commonly used robot configuration, a template can be created so that the Auto Configure mechanism can be used to quickly configure a robot of this type. The logic to detect a runaway op mode (both in the LinearOpMode and OpMode types) and to abort the run, then auto recover has been improved/implemented. Fix has been incorporated so that Logitech F310 gamepad mappings will be correct for Marshmallow users. Release 16.07.08 For the ftc_app project, the gradle files have been modified to support Android Studio 2.1.x. Release 16.03.30 For the MIT App Inventor, the design blocks have new icons that better represent the function of each design component. Some changes were made to the shutdown logic to ensure the robust shutdown of some of our USB services. A change was made to LinearOpMode so as to allow a given instance to be executed more than once, which is required for the App Inventor. Javadoc improved/updated. Release 16.03.09 Changes made to make the FTC SDK synchronous (significant change!) waitOneFullHardwareCycle() and waitForNextHardwareCycle() are no longer needed and have been deprecated. runOpMode() (for a LinearOpMode) is now decoupled from the system's hardware read/write thread. loop() (for an OpMode) is now decoupled from the system's hardware read/write thread. Methods are synchronous. For example, if you call setMode(DcMotorController.RunMode.RESET_ENCODERS) for a motor, the encoder is guaranteed to be reset when the method call is complete. For legacy module (NXT compatible), user no longer has to toggle between read and write modes when reading from or writing to a legacy device. Changes made to enhance reliability/robustness during ESD event. Changes made to make code thread safe. Debug keystore added so that user-generated robot controller APKs will all use the same signed key (to avoid conflicts if a team has multiple developer laptops for example). Firmware version information for Modern Robotics modules are now logged. Changes made to improve USB comm reliability and robustness. Added support for voltage indicator for legacy (NXT-compatible) motor controllers. Changes made to provide auto stop capabilities for op modes. A LinearOpMode class will stop when the statements in runOpMode() are complete. User does not have to push the stop button on the driver station. If an op mode is stopped by the driver station, but there is a run away/uninterruptible thread persisting, the app will log an error message then force itself to crash to stop the runaway thread. Driver Station UI modified to display lowest measured voltage below current voltage (12V battery). Driver Station UI modified to have color background for current voltage (green=good, yellow=caution, red=danger, extremely low voltage). javadoc improved (edits and additional classes). Added app build time to About activity for driver station and robot controller apps. Display local IP addresses on Driver Station About activity. Added I2cDeviceSynchImpl. Added I2cDeviceSync interface. Added seconds() and milliseconds() to ElapsedTime for clarity. Added getCallbackCount() to I2cDevice. Added missing clearI2cPortActionFlag. Added code to create log messages while waiting for LinearOpMode shutdown. Fix so Wifi Direct Config activity will no longer launch multiple times. Added the ability to specify an alternate i2c address in software for the Modern Robotics gyro. Release 16.02.09 Improved battery checker feature so that voltage values get refreshed regularly (every 250 msec) on Driver Station (DS) user interface. Improved software so that Robot Controller (RC) is much more resilient and “self-healing” to USB disconnects: If user attempts to start/restart RC with one or more module missing, it will display a warning but still start up. When running an op mode, if one or more modules gets disconnected, the RC & DS will display warnings,and robot will keep on working in spite of the missing module(s). If a disconnected module gets physically reconnected the RC will auto detect the module and the user will regain control of the recently connected module. Warning messages are more helpful (identifies the type of module that’s missing plus its USB serial number). Code changes to fix the null gamepad reference when users try to reference the gamepads in the init() portion of their op mode. NXT light sensor output is now properly scaled. Note that teams might have to readjust their light threshold values in their op modes. On DS user interface, gamepad icon for a driver will disappear if the matching gamepad is disconnected or if that gamepad gets designated as a different driver. Robot Protocol (ROBOCOL) version number info is displayed in About screen on RC and DS apps. Incorporated a display filter on pairing screen to filter out devices that don’t use the “-“ format. This filter can be turned off to show all WiFi Direct devices. Updated text in License file. Fixed formatting error in OpticalDistanceSensor.toString(). Fixed issue on with a blank (“”) device name that would disrupt WiFi Direct Pairing. Made a change so that the WiFi info and battery info can be displayed more quickly on the DS upon connecting to RC. Improved javadoc generation. Modified code to make it easier to support language localization in the future. Release 16.01.04 Updated compileSdkVersion for apps Prevent Wifi from entering power saving mode removed unused import from driver station Corrrected "Dead zone" joystick code. LED.getDeviceName and .getConnectionInfo() return null apps check for ROBOCOL_VERSION mismatch Fix for Telemetry also has off-by-one errors in its data string sizing / short size limitations error User telemetry output is sorted. added formatting variants to DbgLog and RobotLog APIs code modified to allow for a long list of op mode names. changes to improve thread safety of RobocolDatagramSocket Fix for "missing hardware leaves robot controller disconnected from driver station" error fix for "fast tapping of Init/Start causes problems" (toast is now only instantiated on UI thread). added some log statements for thread life cycle. moved gamepad reset logic inside of initActiveOpMode() for robustness changes made to mitigate risk of race conditions on public methods. changes to try and flag when WiFi Direct name contains non-printable characters. fix to correct race condition between .run() and .close() in ReadWriteRunnableStandard. updated FTDI driver made ReadWriteRunnableStanard interface public. fixed off-by-one errors in Command constructor moved specific hardware implmentations into their own package. moved specific gamepad implemnatations to the hardware library. changed LICENSE file to new BSD version. fixed race condition when shutting down Modern Robotics USB devices. methods in the ColorSensor classes have been synchronized. corrected isBusy() status to reflect end of motion. corrected "back" button keycode. the notSupported() method of the GyroSensor class was changed to protected (it should not be public). Release 15.11.04.001 Added Support for Modern Robotics Gyro. The GyroSensor class now supports the MR Gyro Sensor. Users can access heading data (about Z axis) Users can also access raw gyro data (X, Y, & Z axes). Example MRGyroTest.java op mode included. Improved error messages More descriptive error messages for exceptions in user code. Updated DcMotor API Enable read mode on new address in setI2cAddress Fix so that driver station app resets the gamepads when switching op modes. USB-related code changes to make USB comm more responsive and to display more explicit error messages. Fix so that USB will recover properly if the USB bus returns garbage data. Fix USB initializtion race condition. Better error reporting during FTDI open. More explicit messages during USB failures. Fixed bug so that USB device is closed if event loop teardown method was not called. Fixed timer UI issue Fixed duplicate name UI bug (Legacy Module configuration). Fixed race condition in EventLoopManager. Fix to keep references stable when updating gamepad. For legacy Matrix motor/servo controllers removed necessity of appending "Motor" and "Servo" to controller names. Updated HT color sensor driver to use constants from ModernRoboticsUsbLegacyModule class. Updated MR color sensor driver to use constants from ModernRoboticsUsbDeviceInterfaceModule class. Correctly handle I2C Address change in all color sensors Updated/cleaned up op modes. Updated comments in LinearI2cAddressChange.java example op mode. Replaced the calls to "setChannelMode" with "setMode" (to match the new of the DcMotor method). Removed K9AutoTime.java op mode. Added MRGyroTest.java op mode (demonstrates how to use MR Gyro Sensor). Added MRRGBExample.java op mode (demonstrates how to use MR Color Sensor). Added HTRGBExample.java op mode (demonstrates how to use HT legacy color sensor). Added MatrixControllerDemo.java (demonstrates how to use legacy Matrix controller). Updated javadoc documentation. Updated release .apk files for Robot Controller and Driver Station apps. Release 15.10.06.002 Added support for Legacy Matrix 9.6V motor/servo controller. Cleaned up build.gradle file. Minor UI and bug fixes for driver station and robot controller apps. Throws error if Ultrasonic sensor (NXT) is not configured for legacy module port 4 or 5. Release 15.08.03.001 New user interfaces for FTC Driver Station and FTC Robot Controller apps. An init() method is added to the OpMode class. For this release, init() is triggered right before the start() method. Eventually, the init() method will be triggered when the user presses an "INIT" button on driver station. The init() and loop() methods are now required (i.e., need to be overridden in the user's op mode). The start() and stop() methods are optional. A new LinearOpMode class is introduced. Teams can use the LinearOpMode mode to create a linear (not event driven) program model. Teams can use blocking statements like Thread.sleep() within a linear op mode. The API for the Legacy Module and Core Device Interface Module have been updated. Support for encoders with the Legacy Module is now working. The hardware loop has been updated for better performance.

# big-o-performance A simple html app to demonstrate performance costs of data structures. - Clone the project - Navigate to the root of the project in a termina or command prompt - Run 'npm install' - Run 'npm start' - Go to the URL specified in the terminal or command prompt to try out the app. # This app was created from the Create React App NPM. Below are instructions from that project. Below you will find some information on how to perform common tasks. You can find the most recent version of this guide [here](https://github.com/facebookincubator/create-react-app/blob/master/template/README.md). ## Table of Contents - [Updating to New Releases](#updating-to-new-releases) - [Sending Feedback](#sending-feedback) - [Folder Structure](#folder-structure) - [Available Scripts](#available-scripts) - [npm start](#npm-start) - [npm run build](#npm-run-build) - [npm run eject](#npm-run-eject) - [Displaying Lint Output in the Editor](#displaying-lint-output-in-the-editor) - [Installing a Dependency](#installing-a-dependency) - [Importing a Component](#importing-a-component) - [Adding a Stylesheet](#adding-a-stylesheet) - [Post-Processing CSS](#post-processing-css) - [Adding Images and Fonts](#adding-images-and-fonts) - [Adding Bootstrap](#adding-bootstrap) - [Adding Flow](#adding-flow) - [Adding Custom Environment Variables](#adding-custom-environment-variables) - [Integrating with a Node Backend](#integrating-with-a-node-backend) - [Proxying API Requests in Development](#proxying-api-requests-in-development) - [Deployment](#deployment) - [Now](#now) - [Heroku](#heroku) - [Surge](#surge) - [GitHub Pages](#github-pages) - [Something Missing?](#something-missing) ## Updating to New Releases Create React App is divided into two packages: * `create-react-app` is a global command-line utility that you use to create new projects. * `react-scripts` is a development dependency in the generated projects (including this one). You almost never need to update `create-react-app` itself: it’s delegates all the setup to `react-scripts`. When you run `create-react-app`, it always creates the project with the latest version of `react-scripts` so you’ll get all the new features and improvements in newly created apps automatically. To update an existing project to a new version of `react-scripts`, [open the changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md), find the version you’re currently on (check `package.json` in this folder if you’re not sure), and apply the migration instructions for the newer versions. In most cases bumping the `react-scripts` version in `package.json` and running `npm install` in this folder should be enough, but it’s good to consult the [changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md) for potential breaking changes. We commit to keeping the breaking changes minimal so you can upgrade `react-scripts` painlessly. ## Sending Feedback We are always open to [your feedback](https://github.com/facebookincubator/create-react-app/issues). ## Folder Structure After creation, your project should look like this: ``` my-app/ README.md index.html favicon.ico node_modules/ package.json src/ App.css App.js index.css index.js logo.svg ``` For the project to build, **these files must exist with exact filenames**: * `index.html` is the page template; * `favicon.ico` is the icon you see in the browser tab; * `src/index.js` is the JavaScript entry point. You can delete or rename the other files. You may create subdirectories inside `src`. For faster rebuilds, only files inside `src` are processed by Webpack. You need to **put any JS and CSS files inside `src`**, or Webpack won’t see them. You can, however, create more top-level directories. They will not be included in the production build so you can use them for things like documentation. ## Available Scripts In the project directory, you can run: ### `npm start` Runs the app in the development mode.<br> Open [http://localhost:3000](http://localhost:3000) to view it in the browser. The page will reload if you make edits.<br> You will also see any lint errors in the console. ### `npm run build` Builds the app for production to the `build` folder.<br> It correctly bundles React in production mode and optimizes the build for the best performance. The build is minified and the filenames include the hashes.<br> Your app is ready to be deployed! ### `npm run eject` **Note: this is a one-way operation. Once you `eject`, you can’t go back!** If you aren’t satisfied with the build tool and configuration choices, you can `eject` at any time. This command will remove the single build dependency from your project. Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own. You don’t have to ever use `eject`. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it. ## Displaying Lint Output in the Editor >Note: this feature is available with `react-scripts@0.2.0` and higher. Some editors, including Sublime Text, Atom, and Visual Studio Code, provide plugins for ESLint. They are not required for linting. You should see the linter output right in your terminal as well as the browser console. However, if you prefer the lint results to appear right in your editor, there are some extra steps you can do. You would need to install an ESLint plugin for your editor first. >**A note for Atom `linter-eslint` users** >If you are using the Atom `linter-eslint` plugin, make sure that **Use global ESLint installation** option is checked: ><img src="http://i.imgur.com/yVNNHJM.png" width="300"> Then make sure `package.json` of your project ends with this block: ```js { // ... "eslintConfig": { "extends": "./node_modules/react-scripts/config/eslint.js" } } ``` Projects generated with `react-scripts@0.2.0` and higher should already have it. If you don’t need ESLint integration with your editor, you can safely delete those three lines from your `package.json`. Finally, you will need to install some packages *globally*: ```sh npm install -g eslint babel-eslint eslint-plugin-react eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-flowtype ``` We recognize that this is suboptimal, but it is currently required due to the way we hide the ESLint dependency. The ESLint team is already [working on a solution to this](https://github.com/eslint/eslint/issues/3458) so this may become unnecessary in a couple of months. ## Installing a Dependency The generated project includes React and ReactDOM as dependencies. It also includes a set of scripts used by Create React App as a development dependency. You may install other dependencies (for example, React Router) with `npm`: ``` npm install --save <library-name> ``` ## Importing a Component This project setup supports ES6 modules thanks to Babel. While you can still use `require()` and `module.exports`, we encourage you to use [`import` and `export`](http://exploringjs.com/es6/ch_modules.html) instead. For example: ### `Button.js` ```js import React, { Component } from 'react'; class Button extends Component { render() { // ... } } export default Button; // Don’t forget to use export default! ``` ### `DangerButton.js` ```js import React, { Component } from 'react'; import Button from './Button'; // Import a component from another file class DangerButton extends Component { render() { return <Button color="red" />; } } export default DangerButton; ``` Be aware of the [difference between default and named exports](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281). It is a common source of mistakes. We suggest that you stick to using default imports and exports when a module only exports a single thing (for example, a component). That’s what you get when you use `export default Button` and `import Button from './Button'`. Named exports are useful for utility modules that export several functions. A module may have at most one default export and as many named exports as you like. Learn more about ES6 modules: * [When to use the curly braces?](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281) * [Exploring ES6: Modules](http://exploringjs.com/es6/ch_modules.html) * [Understanding ES6: Modules](https://leanpub.com/understandinges6/read#leanpub-auto-encapsulating-code-with-modules) ## Adding a Stylesheet This project setup uses [Webpack](https://webpack.github.io/) for handling all assets. Webpack offers a custom way of “extending” the concept of `import` beyond JavaScript. To express that a JavaScript file depends on a CSS file, you need to **import the CSS from the JavaScript file**: ### `Button.css` ```css .Button { padding: 20px; } ``` ### `Button.js` ```js import React, { Component } from 'react'; import './Button.css'; // Tell Webpack that Button.js uses these styles class Button extends Component { render() { // You can use them as regular CSS styles return <div className="Button" />; } } ``` **This is not required for React** but many people find this feature convenient. You can read about the benefits of this approach [here](https://medium.com/seek-ui-engineering/block-element-modifying-your-javascript-components-d7f99fcab52b). However you should be aware that this makes your code less portable to other build tools and environments than Webpack. In development, expressing dependencies this way allows your styles to be reloaded on the fly as you edit them. In production, all CSS files will be concatenated into a single minified `.css` file in the build output. If you are concerned about using Webpack-specific semantics, you can put all your CSS right into `src/index.css`. It would still be imported from `src/index.js`, but you could always remove that import if you later migrate to a different build tool. ## Post-Processing CSS This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it. For example, this: ```css .App { display: flex; flex-direction: row; align-items: center; } ``` becomes this: ```css .App { display: -webkit-box; display: -ms-flexbox; display: flex; -webkit-box-orient: horizontal; -webkit-box-direction: normal; -ms-flex-direction: row; flex-direction: row; -webkit-box-align: center; -ms-flex-align: center; align-items: center; } ``` There is currently no support for preprocessors such as Less, or for sharing variables across CSS files. ## Adding Images and Fonts With Webpack, using static assets like images and fonts works similarly to CSS. You can **`import` an image right in a JavaScript module**. This tells Webpack to include that image in the bundle. Unlike CSS imports, importing an image or a font gives you a string value. This value is the final image path you can reference in your code. Here is an example: ```js import React from 'react'; import logo from './logo.png'; // Tell Webpack this JS file uses this image console.log(logo); // /logo.84287d09.png function Header() { // Import result is the URL of your image return <img src={logo} alt="Logo" />; } export default function Header; ``` This works in CSS too: ```css .Logo { background-image: url(./logo.png); } ``` Webpack finds all relative module references in CSS (they start with `./`) and replaces them with the final paths from the compiled bundle. If you make a typo or accidentally delete an important file, you will see a compilation error, just like when you import a non-existent JavaScript module. The final filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will give it a different name in production so you don’t need to worry about long-term caching of assets. Please be advised that this is also a custom feature of Webpack. **It is not required for React** but many people enjoy it (and React Native uses a similar mechanism for images). However it may not be portable to some other environments, such as Node.js and Browserify. If you prefer to reference static assets in a more traditional way outside the module system, please let us know [in this issue](https://github.com/facebookincubator/create-react-app/issues/28), and we will consider support for this. ## Adding Bootstrap You don’t have to use [React Bootstrap](https://react-bootstrap.github.io) together with React but it is a popular library for integrating Bootstrap with React apps. If you need it, you can integrate it with Create React App by following these steps: Install React Bootstrap and Bootstrap from NPM. React Bootstrap does not include Bootstrap CSS so this needs to be installed as well: ``` npm install react-bootstrap --save npm install bootstrap@3 --save ``` Import Bootstrap CSS and optionally Bootstrap theme CSS in the ```src/index.js``` file: ```js import 'bootstrap/dist/css/bootstrap.css'; import 'bootstrap/dist/css/bootstrap-theme.css'; ``` Import required React Bootstrap components within ```src/App.js``` file or your custom component files: ```js import { Navbar, Jumbotron, Button } from 'react-bootstrap'; ``` Now you are ready to use the imported React Bootstrap components within your component hierarchy defined in the render method. Here is an example [`App.js`](https://gist.githubusercontent.com/gaearon/85d8c067f6af1e56277c82d19fd4da7b/raw/6158dd991b67284e9fc8d70b9d973efe87659d72/App.js) redone using React Bootstrap. ## Adding Flow Flow typing is currently [not supported out of the box](https://github.com/facebookincubator/create-react-app/issues/72) with the default `.flowconfig` generated by Flow. If you run it, you might get errors like this: ```js node_modules/fbjs/lib/Deferred.js.flow:60 60: Promise.prototype.done.apply(this._promise, arguments); ^^^^ property `done`. Property not found in 495: declare class Promise<+R> { ^ Promise. See lib: /private/tmp/flow/flowlib_34952d31/core.js:495 node_modules/fbjs/lib/shallowEqual.js.flow:29 29: return x !== 0 || 1 / (x: $FlowIssue) === 1 / (y: $FlowIssue); ^^^^^^^^^^ identifier `$FlowIssue`. Could not resolve name src/App.js:3 3: import logo from './logo.svg'; ^^^^^^^^^^^^ ./logo.svg. Required module not found src/App.js:4 4: import './App.css'; ^^^^^^^^^^^ ./App.css. Required module not found src/index.js:5 5: import './index.css'; ^^^^^^^^^^^^^ ./index.css. Required module not found ``` To fix this, change your `.flowconfig` to look like this: ```ini [libs] ./node_modules/fbjs/flow/lib [options] esproposal.class_static_fields=enable esproposal.class_instance_fields=enable module.name_mapper='^\(.*\)\.css$' -> 'react-scripts/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> 'react-scripts/config/flow/file' suppress_type=$FlowIssue suppress_type=$FlowFixMe ``` Re-run flow, and you shouldn’t get any extra issues. If you later `eject`, you’ll need to replace `react-scripts` references with the `<PROJECT_ROOT>` placeholder, for example: ```ini module.name_mapper='^\(.*\)\.css$' -> '<PROJECT_ROOT>/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> '<PROJECT_ROOT>/config/flow/file' ``` We will consider integrating more tightly with Flow in the future so that you don’t have to do this. ## Adding Custom Environment Variables >Note: this feature is available with `react-scripts@0.2.3` and higher. Your project can consume variables declared in your environment as if they were declared locally in your JS files. By default you will have `NODE_ENV` defined for you, and any other environment variables starting with `REACT_APP_`. These environment variables will be defined for you on `process.env`. For example, having an environment variable named `REACT_APP_SECRET_CODE` will be exposed in your JS as `process.env.REACT_APP_SECRET_CODE`, in addition to `process.env.NODE_ENV`. These environment variables can be useful for displaying information conditionally based on where the project is deployed or consuming sensitive data that lives outside of version control. First, you need to have environment variables defined, which can vary between OSes. For example, let's say you wanted to consume a secret defined in the environment inside a `<form>`: ```jsx render() { return ( <div> <small>You are running this application in <b>{process.env.NODE_ENV}</b> mode.</small> <form> <input type="hidden" defaultValue={process.env.REACT_APP_SECRET_CODE} /> </form> </div> ); } ``` The above form is looking for a variable called `REACT_APP_SECRET_CODE` from the environment. In order to consume this value, we need to have it defined in the environment: ### Windows (cmd.exe) ```cmd set REACT_APP_SECRET_CODE=abcdef&&npm start ``` (Note: the lack of whitespace is intentional.) ### Linux, OS X (Bash) ```bash REACT_APP_SECRET_CODE=abcdef npm start ``` > Note: Defining environment variables in this manner is temporary for the life of the shell session. Setting permanent environment variables is outside the scope of these docs. With our environment variable defined, we start the app and consume the values. Remember that the `NODE_ENV` variable will be set for you automatically. When you load the app in the browser and inspect the `<input>`, you will see its value set to `abcdef`, and the bold text will show the environment provided when using `npm start`: ```html <div> <small>You are running this application in <b>development</b> mode.</small> <form> <input type="hidden" value="abcdef" /> </form> </div> ``` Having access to the `NODE_ENV` is also useful for performing actions conditionally: ```js if (process.env.NODE_ENV !== 'production') { analytics.disable(); } ``` ## Integrating with a Node Backend Check out [this tutorial](https://www.fullstackreact.com/articles/using-create-react-app-with-a-server/) for instructions on integrating an app with a Node backend running on another port, and using `fetch()` to access it. You can find the companion GitHub repository [here](https://github.com/fullstackreact/food-lookup-demo). ## Proxying API Requests in Development >Note: this feature is available with `react-scripts@0.2.3` and higher. People often serve the front-end React app from the same host and port as their backend implementation. For example, a production setup might look like this after the app is deployed: ``` / - static server returns index.html with React app /todos - static server returns index.html with React app /api/todos - server handles any /api/* requests using the backend implementation ``` Such setup is **not** required. However, if you **do** have a setup like this, it is convenient to write requests like `fetch('/api/todos')` without worrying about redirecting them to another host or port during development. To tell the development server to proxy any unknown requests to your API server in development, add a `proxy` field to your `package.json`, for example: ```js "proxy": "http://localhost:4000", ``` This way, when you `fetch('/api/todos')` in development, the development server will recognize that it’s not a static asset, and will proxy your request to `http://localhost:4000/api/todos` as a fallback. Conveniently, this avoids [CORS issues](http://stackoverflow.com/questions/21854516/understanding-ajax-cors-and-security-considerations) and error messages like this in development: ``` Fetch API cannot load http://localhost:4000/api/todos. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled. ``` Keep in mind that `proxy` only has effect in development (with `npm start`), and it is up to you to ensure that URLs like `/api/todos` point to the right thing in production. You don’t have to use the `/api` prefix. Any unrecognized request will be redirected to the specified `proxy`. Currently the `proxy` option only handles HTTP requests, and it won’t proxy WebSocket connections. If the `proxy` option is **not** flexible enough for you, alternatively you can: * Enable CORS on your server ([here’s how to do it for Express](http://enable-cors.org/server_expressjs.html)). * Use [environment variables](#adding-custom-environment-variables) to inject the right server host and port into your app. ## Deployment By default, Create React App produces a build assuming your app is hosted at the server root. To override this, specify the `homepage` in your `package.json`, for example: ```js "homepage": "http://mywebsite.com/relativepath", ``` This will let Create React App correctly infer the root path to use in the generated HTML file. ### Now See [this example](https://github.com/xkawi/create-react-app-now) for a zero-configuration single-command deployment with [now](https://zeit.co/now). ### Heroku Use the [Heroku Buildpack for Create React App](https://github.com/mars/create-react-app-buildpack). You can find instructions in [Deploying React with Zero Configuration](https://blog.heroku.com/deploying-react-with-zero-configuration). ### Surge Install the Surge CLI if you haven't already by running `npm install -g surge`. Run the `surge` command and log in you or create a new account. You just need to specify the *build* folder and your custom domain, and you are done. ```sh email: email@domain.com password: ******** project path: /path/to/project/build size: 7 files, 1.8 MB domain: create-react-app.surge.sh upload: [====================] 100%, eta: 0.0s propagate on CDN: [====================] 100% plan: Free users: email@domain.com IP Address: X.X.X.X Success! Project is published and running at create-react-app.surge.sh ``` Note that in order to support routers that use html5 `pushState` API, you may want to rename the `index.html` in your build folder to `200.html` before deploying to Surge. This [ensures that every URL falls back to that file](https://surge.sh/help/adding-a-200-page-for-client-side-routing). ### GitHub Pages >Note: this feature is available with `react-scripts@0.2.0` and higher. Open your `package.json` and add a `homepage` field: ```js "homepage": "http://myusername.github.io/my-app", ``` **The above step is important!** Create React App uses the `homepage` field to determine the root URL in the built HTML file. Now, whenever you run `npm run build`, you will see a cheat sheet with a sequence of commands to deploy to GitHub pages: ```sh git commit -am "Save local changes" git checkout -B gh-pages git add -f build git commit -am "Rebuild website" git filter-branch -f --prune-empty --subdirectory-filter build git push -f origin gh-pages git checkout - ``` You may copy and paste them, or put them into a custom shell script. You may also customize them for another hosting provider. Note that GitHub Pages doesn't support routers that use the HTML5 `pushState` history API under the hood (for example, React Router using `browserHistory`). This is because when there is a fresh page load for a url like `http://user.github.io/todomvc/todos/42`, where `/todos/42` is a frontend route, the GitHub Pages server returns 404 because it knows nothing of `/todos/42`. If you want to add a router to a project hosted on GitHub Pages, here are a couple of solutions: * You could switch from using HTML5 history API to routing with hashes. If you use React Router, you can switch to `hashHistory` for this effect, but the URL will be longer and more verbose (for example, `http://user.github.io/todomvc/#/todos/42?_k=yknaj`). [Read more](https://github.com/reactjs/react-router/blob/master/docs/guides/Histories.md#histories) about different history implementations in React Router. * Alternatively, you can use a trick to teach GitHub Pages to handle 404 by redirecting to your `index.html` page with a special redirect parameter. You would need to add a `404.html` file with the redirection code to the `build` folder before deploying your project, and you’ll need to add code handling the redirect parameter to `index.html`. You can find a detailed explanation of this technique [in this guide](https://github.com/rafrex/spa-github-pages). ## Something Missing? If you have ideas for more “How To” recipes that should be on this page, [let us know](https://github.com/facebookincubator/create-react-app/issues) or [contribute some!](https://github.com/facebookincubator/create-react-app/edit/master/template/README.md)

minimal tool for creating a new user namespace with multiple UIDs/GIDs mapped inside

SEIS 665 Assignment 2: Linux & Git Overview This week we will focus on becoming familiar with launching a Linux server and working with some basic Linux and Git commands. We will use AWS to launch and host the Linux server. AWS might seem a little confusing at this point. Don’t worry, we will gain much more hands-on experience with AWS throughout the course. The goal is to get you comfortable working with the technology and not overwhelm you with all the details. Requirements You need to have a personal AWS account and GitHub account for this assignment. You should also read the Git Hands-on Guide and Linux Hands-on Guide before beginning this exercise. A word about grading One of the key DevOps practices we learn about in this class is the use of automation to increase the speed and repeatability of processes. Automation is utilized during the assignment grading process to review and assess your work. It’s important that you follow the instructions in each assignment and type in required files and resources with the proper names. All names are case sensitive, so a name like "Web1" is not the same as "web1". If you misspell a name, use the wrong case, or put a file in the wrong directory location you will lose points on your assignment. This is the easiest way to lose points, and also the most preventable. You should always double-check your work to make sure it accurately reflects the requirements specified in the assignment. You should always carefully review the content of your files before submitting your assignment. The assignment Let’s get started! Create GitHub repository The first step in the assignment is to setup a Git repository on GitHub. We will use a special solution called GitHub Classroom for this course which automates the process of setting up student assignment repositories. Here are the basic steps: Click on the following link to open Assignment 2 on the GitHub Classroom site: https://classroom.github.com/a/K4zcVmX- (Links to an external site.)Links to an external site. Click on the Accept this assignment button. GitHub Classroom will provide you with a URL (https) to access the assignment repository. Either copy this address to your clipboard or write it down somewhere. You will need to use this address to set up the repository on a Linux server. Example: https://github.com/UST-SEIS665/hw2-seis665-02-spring2019-<your github id>.git At this point your new repository to ready to use. The repository is currently empty. We will put some content in there soon! Launch Linux server The second step in the assignment is to launch a Linux server using AWS EC2. The server should have the following characteristics: Amazon Linux 2 AMI 64-bit (usually the first option listed) Located in a U.S. region (us-east-1) t2.micro instance type All default instance settings (storage, vpm, security group, etc.) I’ve shown you how to launch EC2 instances in class. You can review it on Canvas. Once you launch the new server, it may take a few minutes to provision. Log into server The next step is to log into the Linux server using a terminal program with a secure shell (SSH) support. You can use iTerm2 (Links to an external site.)Links to an external site. on a Mac and GitBash/PuTTY (Links to an external site.)Links to an external site. on a PC. You will need to have the private server key and the public IP address before attempting to log into the server. The server key is basically your password. If you lose it, you will need to terminate the existing instance and launch a new server. I recommend reusing the same key when launching new servers throughout the class. Note, I make this recommendation to make the learning process easier and not because it is a common security practice. I’ve shown you how to use a terminal application to log into the instance using a Windows desktop. Your personal computer or lab computer may be running a different OS version, but the process is still very similar. You can review the videos on the Canvas. Working with Linux If you’ve made it this far, congratulations! You’ve made it over the toughest hurdle. By the end of this course, I promise you will be able to launch and log into servers in your sleep. You should be looking at a login screen that looks something like this: Last login: Mon Mar 21 21:17:54 2016 from 174-20-199-194.mpls.qwest.net __| __|_ ) _| ( / Amazon Linux AMI ___|\___|___| https://aws.amazon.com/amazon-linux-ami/2015.09-release-notes/ 8 package(s) needed for security, out of 17 available Run "sudo yum update" to apply all updates. ec2-user@ip-172-31-15-26 ~]$ Your terminal cursor is sitting at the shell prompt, waiting for you to type in your first command. Remember the shell? It is a really cool program that lets you start other programs and manage services on the Linux system. The rest of this assignment will be spent working with the shell. Note, when you are asked to type in a command in the steps below, don’t type in the dollar-sign ($) character. This is just meant to represent the command prompt. The actual commands are represented by the characters to the right of the command prompt. Let’s start by asking the shell for some help. Type in: $ help The shell provides you with a list of commands you can run along with possible command options. Next, check out one of the pages in the built-in manual: $ man ls A man page will appear with information on how to use the ls command. This command is used to list the contents of file directories. Either space through the contents of the man page or hit q to exit. Most of the core Linux commands have man pages available. But honestly, some of these man pages are a bit hard to understand. Sometimes your best bet is to search on Google if you are trying to figure out how to use a specific command. When you initially log into Linux, the system places you in your home directory. Each user on the system has a separate home directory. Let’s see where your home directory is located: $ pwd The response should be /home/ec2-user. The pwd command is handy to remember if you ever forget what file directory you are currently located in. If you recall from the Linux Hands-on Guide, this directory is also your current working directory. Type in: $ cd / The cd command let’s you change to a new working directory on the server. In this case, we changed to the root (/) directory. This is the parent of all the other directories on the file system. Type in: $ ls The ls command lists the contents of the current directory. As you can see, root directory contains many other directories. You will become familiar with these directories over time. The ls command provides a very basic directory listing. You need to supply the command with some options if you want to see more detailed information. Type in: $ ls -la See how this command provides you with much more detailed information about the files and directories? You can use this detailed listing to see the owner, group, and access control list settings for each file or directory. Do you see any files listed? Remember, the first character in the access control list column denotes whether a listed item is a file or a directory. You probably see a couple files with names like .autofsck. How come you didn’t see this file when you typed in the lscommand without any options? (Try to run this command again to convince yourself.) Files names that start with a period are called hidden files. These files won’t appear on normal directory listings. Type in: $ cd /var Then, type in: $ ls You will see a directory listing for the /var directory. Next, type in: $ ls .. Huh. This directory listing looks the same as the earlier root directory listing. When you use two periods (..) in a directory path that means you are referring to the parent directory of the current directory. Just think of the two dots as meaning the directory above the current directory. Now, type in: $ cd ~ $ pwd Whoa. We’re back at our home directory again. The tilde character (~) is another one of those handy little directory path shortcuts. It always refers to our personal home directory. Keep in mind that since every user has their own home directory, the tilde shortcut will refer to a unique directory for each logged-in user. Most students are used to navigating a file system by clicking a mouse in nested graphical folders. When they start using a command-line to navigate a file system, they sometimes get confused and lose track of their current position in the file system. Remember, you can always use the pwd command to quickly figure out what directory you are currently working in. Let’s make some changes to the file system. We can easily make our own directories on the file system. Type: mkdir test Now type: ls Cool, there’s our new test directory. Let’s pretend we don’t like that directory name and delete it. Type: rmdir test Now it’s gone. How can you be sure? You should know how to check to see if the directory still exists at this point. Go ahead and check. Let’s create another directory. Type in: $ mkdir documents Next, change to the new directory: $ cd documents Did you notice that your command prompt displays the name of the current directory? Something like: [ec2-user@ip-172-31-15-26 documents]$. Pretty handy, huh? Okay, let’s create our first file in the documents directory. This is just an empty file for training purposes. Type in: $ touch paper.txt Check to see that the new file is in the directory. Now, go back to the previous directory. Remember the double dot shortcut? $ cd .. Okay, we don’t like our documents directory any more. Let’s blow it away. Type in: $ rmdir documents Uh oh. The shell didn’t like that command because the directory isn’t empty. Let’s change back into the documents directory. But this time don’t type in the full name of the directory. You can let shell auto-completion do the typing for you. Type in the first couple characters of the directory name and then hit the tab key: $ cd doc<tab> You should use the tab auto-completion feature often. It saves typing and makes working with the Linux file system much much easier. Tab is your friend. Now, remove the file by typing: $ rm paper.txt Did you try to use the tab key instead of typing in the whole file name? Check to make sure the file was deleted from the directory. Next, create a new file: $ touch file1 We like file1 so much that we want to make a backup copy. Type: $ cp file1 file1-backup Check to make sure the new backup copy was created. We don’t really like the name of that new file, so let’s rename it. Type: $ mv file1-backup backup Moving a file to the same directory and giving it a new name is basically the same thing as renaming it. We could have moved it to a different directory if we wanted. Let’s list all of the files in the current directory that start with the letter f: $ ls f* Using wildcard pattern matching in file commands is really useful if you want the command to impact or filter a group of files. Now, go up one directory to the parent directory (remember the double dot shortcut?) We tried to remove the documents directory earlier when it had files in it. Obviously that won’t work again. However, we can use a more powerful command to destroy the directory and vanquish its contents. Behold, the all powerful remove command: $ rm -fr documents Did you remember to use auto-completion when typing in documents? This command and set of options forcibly removes the directory and its contents. It’s a dangerous command wielded by the mightiest Linux wizards. Okay, maybe that’s a bit of an exaggeration. Just be careful with it. Check to make sure the documents directory is gone before proceeding. Let’s continue. Change to the directory /var and make a directory called test. Ugh. Permission denied. We created this darn Linux server and we paid for it. Shouldn’t we be able to do anything we want on it? You logged into the system as a user called ec2-user. While this user can create and manage files in its home directory, it cannot change files all across the system. At least it can’t as a normal user. The ec2-user is a member of the root group, so it can escalate its privileges to super-user status when necessary. Let’s try it: $ sudo mkdir test Check to make sure the directory exists now. Using sudo we can execute commands as a super-user. We can do anything we want now that we know this powerful new command. Go ahead and delete the test directory. Did you remember to use sudo before the rmdir command? Check to make sure the directory is gone. You might be asking yourself the question: why can we list the contents of the /var directory but not make changes? That’s because all users have read access to the /var directory and the ls command is a read function. Only the root users or those acting as a super-user can write changes to the directory. Let’s go back to our home directory: $ cd ~ Editing text files is a really common task on Linux systems because many of the application configuration files are text files. We can create a text file by using a text editor. Type in: $ nano myfile.conf The shell starts up the nano text editor and places your terminal cursor in the editing screen. Nano is a simple text-based word processor. Type in a few lines of text. When you’re done writing your novel, hit ctrl-x and answer y to the prompt to save your work. Finally, hit enter to save the text to the filename you specified. Check to see that your file was saved in the directory. You can take a look at the contents of your file by typing: $ cat myfile.conf The cat command displays your text file content on the terminal screen. This command works fine for displaying small text files. But if your file is hundreds of lines long, the content will scroll down your terminal screen so fast that you won’t be able to easily read it. There’s a better way to view larger text files. Type in: $ less myfile.conf The less command will page the display of a text file, allowing you to page through the contents of the file using the space bar. Your text file is probably too short to see the paging in action though. Hit q to quit out of the less text viewer. Hit the up-arrow key on your keyboard a few times until the commmand nano myfile.conf appears next to your command prompt. Cool, huh? The up-arrow key allows you to replay a previously run command. Linux maintains a list of all the commands you have run since you logged into the server. This is called the command history. It’s a really useful feature if you have to re-run a complex command again. Now, hit ctrl-c. This cancels whatever command is displayed on the command line. Type in the following command to create a couple empty files in the directory: $ touch file1 file2 file3 Confirm that the files were created. Some commands, like touch. allow you to specify multiple files as arguments. You will find that Linux commands have all kinds of ways to make tasks more efficient like this. Throughout this assignment, we have been running commands and viewing results on the terminal screen. The screen is the standard place for commands to output results. It’s known as the standard out (stdout). However, it’s really useful to output results to the file system sometimes. Type in: $ ls > listing.txt Take a look at the directory listing now. You just created a new file. View the contents of the listing.txt file. What do you see? Instead of sending the output from the ls command to the screen we sent it to a text file. Let’s try another one. Type: $ cat myfile.conf > listing.txt Take a look at the contents of the listing.txt file again. It looks like your myfile.conf file now. It’s like you made a copy of it. But what happened to the previous content in the listing.txt file? When you redirect the output of a command using the right angle-bracket character (>), the output overwrites the existing file. Type this command in: $ cat myfile.conf >> listing.txt Now look at the contents of the listing.txt file. You should see your original content displayed twice. When you use two angle-bracket characters in the commmand the output appends (or adds to) the file instead of overwriting it. We redirected the output from a command to a text file. It’s also possible to redirect the input to a command. Typically we use a keyboard to provide input, but sometimes it makes more sense to input a file to a command. For example, how many words are in your new listing.txt file? Let’s find out. Type in: $ wc -w < listing.txt Did you get a number? This command inputs the listing.txt file into a word count program called wc. Type in the command: $ ls /usr/bin The terminal screen probably scrolled quickly as filenames flashed by. The /usr/bin directory holds quite a few files. It would be nice if we could page through the contents of this directory. Well, we can. We can use a special shell feature called pipes. In previous steps, we redirected I/O using the file system. Pipes allow us to redirect I/O between programs. We can redirect the output from one program into another. Type in: $ ls /usr/bin | less Now the directory listing is paged. Hit the spacebar to page through the listing. The pipe, represented by a vertical bar character (|), takes the output from the ls command and redirects it to the less command where the resulting output is paged. Pipes are super powerful and used all the time by savvy Linux operators. Hit the q key to quit the paginated directory listing command. Working with shell scripts Now things are going to get interesting. We’ve been manually typing in commands throughout this exercise. If we were running a set of repetitive tasks, we would want to automate the process as much as possible. The shell makes it really easy to automate tasks using shell scripts. The shell provides many of the same features as a basic procedural programming language. Let’s write some code. Type in this command: $ j=123 $ echo $j We just created a variable named j referencing the string 123. The echo command printed out the value of the variable. We had to use a dollar sign ($) when referencing the variable in another command. Next, type in: $ j=1+1 $ echo $j Is that what you expected? The shell just interprets the variable value as a string. It’s not going to do any sort of computation. Typing in shell script commands on the command line is sort of pointless. We want to be able to create scripts that we can run over-and-over. Let’s create our first shell script. Use the nano editor to create a file named myscript. When the file is open in the editor, type in the following lines of code: #!/bin/bash echo Hello $1 Now quit the editor and save your file. We can run our script by typing: $ ./myscript World Er, what happened? Permission denied. Didn’t we create this file? Why can’t we run it? We can’t run the script file because we haven’t set the execute permission on the file. Type in: $ chmod u+x myscript This modifies the file access control list to allow the owner of the file to execute it. Let’s try to run the command again. Hit the up-arrow key a couple times until the ./myscript World command is displayed and hit enter. Hooray! Our first shell script. It’s probably a bit underwhelming. No problem, we’ll make it a little more complex. The script took a single argument called World. Any arguments provided to a shell script are represented as consecutively numbered variables inside the script ($1, $2, etc). Pretty simple. You might be wondering why we had to type the ./ characters before the name of our script file. Try to type in the command without them: $ myscript World Command not found. That seems a little weird. Aren’t we currently in the directory where the shell script is located? Well, that’s just not how the shell works. When you enter a command into the shell, it looks for the command in a predefined set of directories on the server called your PATH. Since your script file isn’t in your special path, the shell reports it as not found. By typing in the ./ characters before the command name you are basically forcing the shell to look for your script in the current directory instead of the default path. Create another file called cleanup using nano. In the file editor window type: #!/bin/bash # My cleanup script mkdir archive mv file* archive Exit the editor window and save the file. Change the permissions on the script file so that you can execute it. Now run the command: $ ./cleanup Take a look at the file directory listing. Notice the archive directory? List the contents of that directory. The script automatically created a new directory and moved three files into it. Anything you can do manually at a command prompt can be automated using a shell script. Let’s create one more shell script. Use nano to create a script called namelist. Here is the content of the script: #!/bin/bash # for-loop test script names='Jason John Jane' for i in $names do echo Hello $i done Change the permissions on the script file so that you can execute it. Run the command: $ ./namelist The script will loop through a set of names stored in a variable displaying each one. Scripts support several programming constructs like for-loops, do-while loops, and if-then-else. These building blocks allow you to create fairly complex scripts for automating tasks. Installing packages and services We’re nearing the end of this assignment. But before we finish, let’s install some new software packages on our server. The first thing we should do is make sure all the current packages installed on our Linux server are up-to-date. Type in: $ sudo yum update -y This is one of those really powerful commands that requires sudo access. The system will review the currently installed packages and go out to the Internet and download appropriate updates. Next, let’s install an Apache web server on our system. Type in: $ sudo yum install httpd -y Bam! You probably never knew that installing a web server was so easy. We’re not going to actually use the web server in this exercise, but we will in future assignments. We installed the web server, but is it actually running? Let’s check. Type in: $ sudo service httpd status Nope. Let’s start it. Type: $ sudo service httpd start We can use the service command to control the services running on the system. Let’s setup the service so that it automatically starts when the system boots up. Type in: $ sudo chkconfig httpd on Cool. We installed the Apache web server on our system, but what other programs are currently running? We can use the pscommand to find out. Type in: $ ps -ax Lots of processes are running on our system. We can even look at the overall performance of our system using the topcommand. Let’s try that now. Type in: $ top The display might seem a little overwhelming at first. You should see lots of performance information displayed including the cpu usage, free memory, and a list of running tasks. We’re almost across the finish line. Let’s make sure all of our valuable work is stored in a git repository. First, we need to install git. Type in the command: $ sudo yum install git -y Check your work It’s very important to check your work before submitting it for grading. A misspelled, misplaced or missing file will cost you points. This may seem harsh, but the reality is that these sorts of mistakes have consequences in the real world. For example, a server instance could fail to launch properly and impact customers because a single required file is missing. Here is what the contents of your git repository should look like before final submission: ┣archive ┃ ┣ file1 ┃ ┣ file2 ┃ ┗ file3 ┣ namelist ┗ myfile.conf Saving our work in the git repository Next, make sure you are still in your home directory (/home/ec2-user). We will install the git repository you created at the beginning of this exercise. You will need to modify this command by typing in the GitHub repository URL you copied earlier. $ git clone <your GitHub URL here>.git Example: git clone https://github.com/UST-SEIS665/hw2-seis665-02-spring2019-<your github id>.git The git application will ask you for your GitHub username and password. Note, if you have multi-factor authentication enabled on your GitHub account you will need to provide a personal token instead of your password. Git will clone (copy) the repository from GitHub to your Linux server. Since the repository is empty the clone happens almost instantly. Check to make sure that a sub-directory called "hw2-seis665-02-spring2019-<username>" exists in the current directory (where <username> is your GitHub account name). Git automatically created this directory as part of the cloning process. Change to the hw2-seis665-02-spring2019-<username> directory and type: $ ls -la Notice the .git hidden directory? This is where git actually stores all of the file changes in your repository. Nothing is actually in your repository yet. Change back to the parent directory (cd ..). Next, let’s move some of our files into the repository. Type: $ mv archive hw2-seis665-02-spring2019-<username> $ mv namelist hw2-seis665-02-spring2019-<username> $ mv myfile.conf hw2-seis665-02-spring2019-<username> Hopefully, you remembered to use the auto-complete function to reduce some of that typing. Change to the hw2-seis665-02-spring2019-<username> directory and list the directory contents. Your files are in the working directory, but are not actually stored in the repository because they haven’t been committed yet. Type in: $ git status You should see a list of untracked files. Let’s tell git that we want these files tracked. Type in: $ git add * Now type in the git status command again. Notice how all the files are now being tracked and are ready to be committed. These files are in the git staging area. We’ll commit them to the repository next. Type: $ git commit -m 'assignment 2 files' Next, take a look at the commit log. Type: $ git log You should see your commit listed along with an assigned hash (long string of random-looking characters). Finally, let’s save the repository to our GitHub account. Type in: $ git push origin master The git client will ask you for your GitHub username and password before pushing the repository. Go back to the GitHub.com website and login if you have been logged out. Click on the repository link for the assignment. Do you see your files listed there? Congratulations, you completed the exercise! Terminate server The last step is to terminate your Linux instance. AWS will bill you for every hour the instance is running. The cost is nominal, but there’s no need to rack up unnecessary charges. Here are the steps to terminate your instance: Log into your AWS account and click on the EC2 dashboard. Click the Instances menu item. Select your server in the instances table. Click on the Actions drop down menu above the instances table. Select the Instance State menu option Click on the Terminate action. Your Linux instance will shutdown and disappear in a few minutes. The EC2 dashboard will continue to display the instance on your instance listing for another day or so. However, the state of the instance will be terminated. Submitting your assignment — IMPORTANT! If you haven’t already, please e-mail me your GitHub username in order to receive credit for this assignment. There is no need to email me to tell me that you have committed your work to GitHub or to ask me if your GitHub submission worked. If you can see your work in your GitHub repository, I can see your work.

Overview For this assignment you will be developing an application that uses raw IP sockets to ‘walk’ around an ordered list of nodes (given as a command line argument at the ‘source’ node, which is the node at which the tour was initiated), in a manner similar to the IP SSRR (Strict Source and Record Route) option. At each node, the application pings the preceding node in the tour. However, unlike the ping code in Stevens, you will be sending the ping ICMP echo request messages through a SOCK_RAW-type PF_PACKET socket and implementing ARP functionality to find the Ethernet address of the target node. Finally, when the ‘walk’ is completed, the group of nodes visited on the tour will exchange multicast messages. Your code will consist of two process modules, a ‘Tour’ application module (which will implement all the functionality outlined above, except for ARP activity) and an ARP module. The following should prove to be useful reference material for the assignment: Sections 21.2, 21.3, 21.6 and 21.10, Chapter 21, on Multicasting. Sections 27.1 to 27.3, Chapter 27, on the IP SSRR option. Sections 28.1 to 28.5, Chapter 28, on raw sockets, the IP_HDRINCL socket option, and ping. Sections 15.5, Chapter 15, on Unix domain SOCK_STREAM sockets. Figure 29.14, p. 807, and the corresponding explanation on p. 806, on filling in an IP header when the IP_HDRINCL socket option is in effect. The Lecture Slides on ARP & RARP (especially Section 4.4, ARP Packet Format, and the Figure 4.3 it includes). The link http://www.pdbuchan.com/rawsock/rawsock.html contains useful code samples that use IP raw sockets and PF_PACKET sockets. Note, in partcular, the code “icmp4_ll.c” in Table 2 for building an echo request sent through a PF_PACKET SOCK_RAW socket. The VMware environment You will be using the same vm1 , . . . . . , vm10 nodes you used for Assignment 3. However, unlike Assignment 3, you should use only interfaces eth0 and their associated IP addresses and ignore the other Ethernet interfaces that nodes have (interfaces eth0 make vm1 , . . . . . , vm10 look as if they belong to the same Ethernet LAN segment IP network 130.245.156.0/24). Note that, apart from the primary IP addresses associated with interfaces eth0, some nodes might also have one or more alias IP addresses associated with their interface eth0. Tour application module specifications The application will create a total of four sockets: two IP raw sockets, a PF_PACKET socket and a UDP socket for multicasting. We shall call the two IP raw sockets the ‘rt ’ (‘route traversal’) and ‘pg ’ (‘ping’) sockets, respectively. The rt socket should have the IP_HDRINCL option set. You will only be receiving ICMP echo reply messages through the pg socket (and not sending echo requests), so it does not matter whether it has the IP_HDRINCL option set or not. The pg socket should have protocol value (i.e., protocol demultiplexing key in the IP header) IPPROTO_ICMP. The rt socket should have a protocol value that identifies the application - i.e., some value other than the IPPROTO_XXXX values in /usr/include/netinet/in.h. However, remember that you will all be running your code using the same root account on the vm1 , . . . . . , vm10 nodes. So if two of you happen to choose the same protocol value and happen to be running on the same vm node at the same time, your applications will receive each other’s IP packets. For that reason, try to choose a protocol value for your rt socket that is likely to be unique to yourself. The PF_PACKET socket should be of type SOCK_RAW (not SOCK_DGRAM). This socket should have a protocol value of ETH_P_IP = 0x0800 (IPv4). The UDP socket for multicasting will be discussed below. Note that, depending on how you choose to bind that socket, you might actually need to have two UDP sockets for multicast communication – see bottom of p. 576, Section 21.10. Your application will, of course, have to be running on every vm node that is included in the tour. When evoking the application on the source node, the user supplies a sequence of vm node names (not IP addresses) to be visited in order. This command line sequence starts with the next node to be visited from the source node (i.e., it does not start with the source node itself). The sequence can include any number of repeated visits to the same node. For example, suppose that the source node is vm3 and the executable is called badr_tour : [root@vm3/root]# badr_tour vm2 vm10 vm4 vm7 vm5 vm2 vm6 vm2 vm9 vm4 vm7 vm2 vm6 vm5 vm1 vm10 vm8 (but note that the tour does not necessarily have to visit every vm node; and the same node should not appear consequentively in the tour list – i.e., the next node on the tour cannot be the current node itself). The application turns the sequence into a list of IP addresses for source routing. It also adds the IP address of the source node itself to the beginning of the list. The list thus produced will be carried as the payload of an IP packet, not as a SSRR option in the packet header. It is our application which will ensure that every node in the sequence is visited in order, not the IP SSRR capability. The source node should also add to the list an IP multicast address and a port number of its choice. It should also join the multicast group at that address and port number on its UDP socket. The TTL for outgoing multicasts should be set to 1. The application then fills in the header of an IP packet, designating itself as the IP source, and the next node to be visited as the IP destination. The packet is sent out on the rt socket. Note that on Linux, all the fields of the packet header must be in network byte order (Stevens, Section 28.3, p. 737, the fourth bullet point). When filling in the packet header, you should explicitly fill in the identification field (recall that, with the IP_HDRINCL socket option, if the identification field is given value 0, then the kernel will set its value). Try to make sure that the value you choose is likely to be unique to yourself (for reasons similar to those explained with respect to the IPPROTO_XXXX in 1. above). When a node receives an IP packet on its rt socket, it should first check that the identification field carries the right value (this implies that you will hard code your choice of identification field value determined in item 2 above in your code). If the identification field value does not check out, the packet is ignored. For a valid packet : Print out a message along the lines of: <time> received source routing packet from <hostname> <time> is the current time in human-readable format (see lines 19 & 20 in Figure 1.9, p. 14, and the corresponding explanation on p. 14f.), and <hostname> is the host name corresponding to the source IP address in the header of the received packet. If this is the first time the node is visited, the application should use the multicast address and port number in the packet received to join the multicast group on its UDP socket. The TTL for outgoing multicasts should be set to 1. The application updates the list in the payload, so that the next node in the tour can easily identify what the next hop from itself will be when it receives the packet. How you do this I leave up to you. You could, for example, include as part of the payload a pointer field into the list of nodes to be visited. This pointer would then be updated to the next entry in the list as the packet progresses hop by hop (see Figure 27.1 and the associated explanation on pp. 711-712). Other solutions are, of course, possible. The application then fills in a new IP header, designating itself as the IP source, and the next node to be visited as the IP destination. The identification field should be set to the same value as in the received packet. The packet is sent out on the rt socket. The node should also initiate pinging to the preceding node in the tour (the IP address of which it should pick up from the header of the received packet). However, unlike the Stevens ping code, it will be using the SOCK_RAW-type PF_PACKET socket of item 1 above to send the ICMP echo request messages. Before it can send echo request messages, the application has to call on the ARP module you will implement to get the Ethernet address of this preceding / ‘target’ node; this call is made using the API function areq which you will also implement (see sections ARP module specifications & API specifications below). Note that ARP has to be evoked every time the application wants to send out an echo request message, and not just the first time. An echo request message has to be encapsulated in a properly-formulated IP packet, which is in turn encapsulated in a properly-formulated Ethernet frame transmitted out through the PF_PACKET socket ; otherwise, ICMP at the source node will not receive it. You will have to modify Stevens’ ping code accordingly, specifically, the send_v4 function. In particular, the Ethernet frame must have a value of ETH_P_IP = 0x0800 (IPv4 – see <linux/if_ether.h>) in the frame type / ‘length’ field ; and the encapsulated IP packet must have a value of IPPROTO_ICMP = 0x01 (ICMPv4 – see <netinet_in.h>) in its protocol field. You should also simplify the ping code in its entirety by stripping all the ‘indirection’ IPv4 / IPv6 dual-operability paraphernalia and making the code work just for IPv4. Also note that the functions host_serv and freeaddrinfo, together with the associated structure addrinfo (see Sections 11.6, 11.8 & 11.11), in Figures 27.3, 27.6 & 28.5 ( pp. 713, 716 & 744f., respectively) can be replaced by the function gethostbyname and associated structure hostent (see Section 11.3) where needed. Also, there is no ‘-v’ verbose option, so this too should be stripped from Stevens’ code. When a node is ready to start pinging, it first prints out a ‘PING’ message similar to lines 32-33 of Figure 28.5, p. 744. It then builds up ICMP echo request messages and sends them to the source node every 1 second through the PF_PACKET socket. It also reads incoming echo response messages off the pg socket, in response to which it prints out the same kind of output as the code of Figure 28.8, p. 748. If this node and its preceding node have been previously visited in that order during the tour, then pinging would have already been initiated from the one to the other in response to the first visit, and nothing further should nor need be done during second and subsequent visits. In light of the above, note that once a node initiates pinging, it needs to read from both its rt and pg sockets, necessitating the use of the select function. As will be clear from what follows below, the application will anyway be needing also to simultaneously monitor its UDP socket for incoming multicast datagrams. When the last node on the tour is reached, and if this is the first time it is visited, it joins the multicast group and starts pinging the preceding node (if it is not already doing so). After a few echo replies are received (five, say), it sends out the multicast message below on its UDP socket (i.e., the node should wait about five seconds before sending the multicast message) : <<<<< This is node vmi . Tour has ended . Group members please identify yourselves. >>>>> where vmi is the name (not IP address) of the node. The node should also print this message out on stdout preceded, on the same line, by the phrase: Node vmi . Sending: <then print out the message sent>. Each node vmj receiving this message should print out the message received preceded, on the same line, by the phrase: Node vmj . Received <then print out the message received>. Each such node in step a above should then immediately stop its pinging activity. The node should then send out the following multicast message: <<<<< Node vmj . I am a member of the group. >>>>> and print out this message preceded, on the same line, by the phrase: Node vmj . Sending: <then print out the message sent>. Each node receiving these second multicast messages (i.e., the messages that nodes – including itself – sent out in step c above) should print each such message out preceded, on the same line, by the phrase: Node vmk . Received: <then print out the message received>. Reading from the socket in step d above should be implemented with a 5-second timeout. When the timeout expires, the node should print out another message to the effect that it is terminating the Tour application, and gracefully exit its Tour process. Note that under Multicast specifications, the last node in the tour, which sends out the End of Tour message, should itself receive a copy of that message and, when it does, it should behave exactly as do the other nodes in steps a. – e. above. ARP module specifications Your executable is evoked with no command line arguments. Like the Tour module, it will be running on every vm node. It uses the get_hw_addrs function of Assignment 3 to explore its node’s interfaces and build a set of <IP address , HW address> matching pairs for all eth0 interface IP addresses (including alias IP addresses, if any). Write out to stdout in some appropriately clear format the address pairs found. The module creates two sockets: a PF_PACKET socket and a Unix domain socket. The PF_PACKET should be of type SOCK_RAW (not type SOCK_DGRAM) with a protocol value of your choice (but not one of the standard values defined in <linux/if_ether.h>) which is, hopefully, unique to yourself. This value effectively becomes the protocol value for your implementation of ARP. Because this protocol value will be carried in the frame type / ‘length’ field of the Ethernet frame header (see Figure 4.3 of the ARP & RARP handout), the value chosen should be not less than 1536 (0x600) so that it is not misinterpreted as the length of an Ethernet 802.3 frame. The Unix domain socket should be of type SOCK_STREAM (not SOCK_DGRAM). It is a listening socket bound to a ‘well-known’ sun_path file. This socket will be used to communicate with the function areq that is implemented in the Tour module (see the section API specifications below). In this context, areq will act as the client and the ARP module as the server. The ARP module then sits in an infinite loop, monitoring these two sockets. As ARP request messages arrive on the PF_PACKET socket, the module processes them, and responds with ARP reply messages as appropriate. The protocol builds a ‘cache’ of matching <IP address , HW address> pairs from the replies (and requests – see below) it receives. For simplicity, and unlike the real ARP, we shall not implement timing out mechanisms for these cache entries. A cache entry has five parts: (i) IP address ; (ii) HW address ; (iii) sll_ifindex (the interface to be used for reaching the matching pair <(i) , (ii)>) ; (iv) sll_hatype ; and (v) a Unix-domain connection-socket descriptor for a connected client (see the section API specifications below for the latter three). When an ARP reply is being entered in the cache, the ARP module uses the socket descriptor in (v) to send a reply to the client, closes the connection socket, and deletes the socket descriptor from the cache entry. Note that, like the real ARP, when an ARP request is received by a node, and if the request pertains to that receiving node, the sender’s (see Figure 4.3 of the ARP & RARP handout) <IP address, HW address> matching pair should be entered into the cache if it is not already there (together, of course, with (iii) sll_ifindex & (iv) sll_hatype), or updated if need be if such an entry already exists in the cache. If the ARP request received does not pertain to the node receiving it, but there is already an entry in that receiving node's cache for the sender’s <IP address, HW address> matching pair, that entry should be checked and updated if need be. If there is no such entry, no action is taken (in particular, and unlike the case above, no new entry should be made in the receiving node's cache of the sender’s <IP address, HW address> matching pair if such an entry does not already exist). ARP request and reply messages have the same format as Figure 4.3 of the ARP & RARP handout, but with an extra 2-byte identification field added at the beginning which you fill with a value chosen so that it has a high probability of being unique to yourself. This value is to be echoed in the reply message, and helps to act as a further filter in case some other student happens to have fortuitously chosen the same value as yourself for the protocol parameter of the ARP PF_PACKET. Values in the fields of our ARP messages must be in network byte order. You might find the system header file <linux/if_arp.h> useful for manipulating ARP request and reply messages, but remember that our version of these messages have an extra two-byte field as mentioned above. Your code should print out on stdout, in some appropriately clear format, the contents of the Ethernet frame header and ARP request message you send. As described in Section 4.4 of the ARP & RARP handout, the node that responds to the request should, in its reply message, swap the two sender addresses with the two target addresses, as well as, of course, echo back the extra identification field sent with the request. The protocol at this responding node should print out, in an appropriately clear format, both the request frame (header and ARP message) it receives and the reply frame it sends. Similarly, the node that sent the request should print out the reply frame it receives. Finally, recall that the node issuing the request sends out a broadcast Ethernet frame, but the responding node replies with a unicast frame. API specifications The API is for communication between the Tour process and the ARP process. It consists of a single function, areq, implemented in the Tour module. areq is called by send_v4 function of the application every time the latter want to send out an ICMP echo request message: int areq (struct sockaddr *IPaddr, socklen_t sockaddrlen, struct hwaddr *HWaddr); IPaddr contains the primary or alias IPaddress of a ‘target’ node on the LAN for which the corresponding hardware address is being requested. hwaddr is a new structure (and not a pre-existing type) modeled on the sockaddr_ll of PF_PACKET; you will have to declare it in your code. It is used to return the requested hardware address to the caller of areq : structure hwaddr { int sll_ifindex; /* Interface number */ unsigned short sll_hatype; /* Hardware type */ unsigned char sll_halen; /* Length of address */ unsigned char sll_addr[8]; /* Physical layer address */ }; areq creates a Unix domain socket of type SOCK_STREAM and connects to the ‘well-known’ sun_path file of the ARP listening socket. It sends the IP address from parameter IPaddr and the information in the three fields of parameter HWaddr to ARP. It then blocks on a read awaiting a reply from ARP. This read should be backed up by a timeout since it is possible that no reply is received for the request. If a timeout occurs, areq should close the socket and return to its caller indicating failure (through its int return value). Your application code should print out on stdout, in some appropriately clear format, a notification every time areq is called, giving the IP address for which a HW address is being sought. It should similarly print out the result when the call to areq returns (HW address returned, or failure). When the ARP module receives a request for a HW address from areq through its Unix domain listening socket, it first checks if the required HW address is already in the cache. If so, it can respond immediately to the areq and close the Unix domain connection socket. Else : it makes an ‘incomplete’ entry in the cache, consisting of parts (i), (iii), (iv) and (v) ; puts out an ARP request message on the network on its PF_PACKET socket; and starts monitoring the areq connection socket for readability – if the areq client closes the connection socket (this would occur in response to a timeout in areq), ARP deletes the corresponding incomplete entry from the cache (and ignores any subsequent ARP reply from the network if such is received). On the other hand, if ARP receives a reply from the network, it updates the incomplete cache entry, responds to areq, and closes the connection socket.

According to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because beAccording to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because bees don't care what humans think is impossible. Yellow, black. Yellow, black. Yellow, black. Yellow, black. Ooh, black and yellow! Let's shake it up a little. Barry! Breakfast is ready! Ooming! Hang on a second. Hello? - Barry? - Adam? - Oan you believe this is happening? - I can't. I'll pick you up. Looking sharp. Use the stairs. Your father paid good money for those. Sorry. I'm excited. Here's the graduate. We're very proud of you, son. A perfect report card, all B's. Very proud. Ma! I got a thing going here. - You got lint on your fuzz. - Ow! That's me! - Wave to us! We'll be in row 118,000. - Bye! Barry, I told you, stop flying in the house! - Hey, Adam. - Hey, Barry. - Is that fuzz gel? - A little. Special day, graduation. Never thought I'd make it. Three days grade school, three days high school. Those were awkward. Three days college. I'm glad I took a day and hitchhiked around the hive. You did come back different. - Hi, Barry. - Artie, growing a mustache? Looks good. - Hear about Frankie? - Yeah. - You going to the funeral? - No, I'm not going. Everybody knows, sting someone, you die. Don't waste it on a squirrel. Such a hothead. I guess he could have just gotten out of the way. I love this incorporating an amusement park into our day. That's why we don't need vacations. Boy, quite a bit of pomp... under the circumstances. - Well, Adam, today we are men. - We are! - Bee-men. - Amen! Hallelujah! Students, faculty, distinguished bees, please welcome Dean Buzzwell. Welcome, New Hive Oity graduating class of... ...9:15. That concludes our ceremonies. And begins your career at Honex Industries! Will we pick ourjob today? I heard it's just orientation. Heads up! Here we go. Keep your hands and antennas inside the tram at all times. - Wonder what it'll be like? - A little scary. Welcome to Honex, a division of Honesco and a part of the Hexagon Group. This is it! Wow. Wow. We know that you, as a bee, have worked your whole life to get to the point where you can work for your whole life. Honey begins when our valiant Pollen Jocks bring the nectar to the hive. Our top-secret formula is automatically color-corrected, scent-adjusted and bubble-contoured into this soothing sweet syrup with its distinctive golden glow you know as... Honey! - That girl was hot. - She's my cousin! - She is? - Yes, we're all cousins. - Right. You're right. - At Honex, we constantly strive to improve every aspect of bee existence. These bees are stress-testing a new helmet technology. - What do you think he makes? - Not enough. Here we have our latest advancement, the Krelman. - What does that do? - Oatches that little strand of honey that hangs after you pour it. Saves us millions. Oan anyone work on the Krelman? Of course. Most bee jobs are small ones. But bees know that every small job, if it's done well, means a lot. But choose carefully because you'll stay in the job you pick for the rest of your life. The same job the rest of your life? I didn't know that. What's the difference? You'll be happy to know that bees, as a species, haven't had one day off in 27 million years. So you'll just work us to death? We'll sure try. Wow! That blew my mind! "What's the difference?" How can you say that? One job forever? That's an insane choice to have to make. I'm relieved. Now we only have to make one decision in life. But, Adam, how could they never have told us that? Why would you question anything? We're bees. We're the most perfectly functioning society on Earth. You ever think maybe things work a little too well here? Like what? Give me one example. I don't know. But you know what I'm talking about. Please clear the gate. Royal Nectar Force on approach. Wait a second. Oheck it out. - Hey, those are Pollen Jocks! - Wow. I've never seen them this close. They know what it's like outside the hive. Yeah, but some don't come back. - Hey, Jocks! - Hi, Jocks! You guys did great! You're monsters! You're sky freaks! I love it! I love it! - I wonder where they were. - I don't know. Their day's not planned. Outside the hive, flying who knows where, doing who knows what. You can'tjust decide to be a Pollen Jock. You have to be bred for that. Right. Look. That's more pollen than you and I will see in a lifetime. It's just a status symbol. Bees make too much of it. Perhaps. Unless you're wearing it and the ladies see you wearing it. Those ladies? Aren't they our cousins too? Distant. Distant. Look at these two. - Oouple of Hive Harrys. - Let's have fun with them. It must be dangerous being a Pollen Jock. Yeah. Once a bear pinned me against a mushroom! He had a paw on my throat, and with the other, he was slapping me! - Oh, my! - I never thought I'd knock him out. What were you doing during this? Trying to alert the authorities. I can autograph that. A little gusty out there today, wasn't it, comrades? Yeah. Gusty. We're hitting a sunflower patch six miles from here tomorrow. - Six miles, huh? - Barry! A puddle jump for us, but maybe you're not up for it. - Maybe I am. - You are not! We're going 0900 at J-Gate. What do you think, buzzy-boy? Are you bee enough? I might be. It all depends on what 0900 means. Hey, Honex! Dad, you surprised me. You decide what you're interested in? - Well, there's a lot of choices. - But you only get one. Do you ever get bored doing the same job every day? Son, let me tell you about stirring. You grab that stick, and you just move it around, and you stir it around. You get yourself into a rhythm. It's a beautiful thing. You know, Dad, the more I think about it, maybe the honey field just isn't right for me. You were thinking of what, making balloon animals? That's a bad job for a guy with a stinger. Janet, your son's not sure he wants to go into honey! - Barry, you are so funny sometimes. - I'm not trying to be funny. You're not funny! You're going into honey. Our son, the stirrer! - You're gonna be a stirrer? - No one's listening to me! Wait till you see the sticks I have. I could say anything right now. I'm gonna get an ant tattoo! Let's open some honey and celebrate! Maybe I'll pierce my thorax. Shave my antennae. Shack up with a grasshopper. Get a gold tooth and call everybody "dawg"! I'm so proud. - We're starting work today! - Today's the day. Oome on! All the good jobs will be gone. Yeah, right. Pollen counting, stunt bee, pouring, stirrer, front desk, hair removal... - Is it still available? - Hang on. Two left! One of them's yours! Oongratulations! Step to the side. - What'd you get? - Picking crud out. Stellar! Wow! Oouple of newbies? Yes, sir! Our first day! We are ready! Make your choice. - You want to go first? - No, you go. Oh, my. What's available? Restroom attendant's open, not for the reason you think. - Any chance of getting the Krelman? - Sure, you're on. I'm sorry, the Krelman just closed out. Wax monkey's always open. The Krelman opened up again. What happened? A bee died. Makes an opening. See? He's dead. Another dead one. Deady. Deadified. Two more dead. Dead from the neck up. Dead from the neck down. That's life! Oh, this is so hard! Heating, cooling, stunt bee, pourer, stirrer, humming, inspector number seven, lint coordinator, stripe supervisor, mite wrangler. Barry, what do you think I should... Barry? Barry! All right, we've got the sunflower patch in quadrant nine... What happened to you? Where are you? - I'm going out. - Out? Out where? - Out there. - Oh, no! I have to, before I go to work for the rest of my life. You're gonna die! You're crazy! Hello? Another call coming in. If anyone's feeling brave, there's a Korean deli on 83rd that gets their roses today. Hey, guys. - Look at that. - Isn't that the kid we saw yesterday? Hold it, son, flight deck's restricted. It's OK, Lou. We're gonna take him up. Really? Feeling lucky, are you? Sign here, here. Just initial that. - Thank you. - OK. You got a rain advisory today, and as you all know, bees cannot fly in rain. So be careful. As always, watch your brooms, hockey sticks, dogs, birds, bears and bats. Also, I got a couple of reports of root beer being poured on us. Murphy's in a home because of it, babbling like a cicada! - That's awful. - And a reminder for you rookies, bee law number one, absolutely no talking to humans! All right, launch positions! Buzz, buzz, buzz, buzz! Buzz, buzz, buzz, buzz! Buzz, buzz, buzz, buzz! Black and yellow! Hello! You ready for this, hot shot? Yeah. Yeah, bring it on. Wind, check. - Antennae, check. - Nectar pack, check. - Wings, check. - Stinger, check. Scared out of my shorts, check. OK, ladies, let's move it out! Pound those petunias, you striped stem-suckers! All of you, drain those flowers! Wow! I'm out! I can't believe I'm out! So blue. I feel so fast and free! Box kite! Wow! Flowers! This is Blue Leader. We have roses visual.You wrote that yourself? wow congrats dude, really, that's very cool. i just told everyone in my family about it, everybody thinks that's very impressive and asked me to congratulate you. they want to speak to you in person, if possible, to give you their regards. they also said they will tell our distant relatives in christmas supper and in NYE they will ignite fireworks that spell your name. i also told about this enormous deed to closer relatives, they had the same reaction. they asked for your address so they can send congratulatory cards and messages. my friends didn't believe me when i told them i knew the author of this gigantic feat, really, they were dumbstruck, they said they will make your name echo through years and years to come. when my neighbour found out about what you did, he was completely dumbstruck too, he wanted to know who you are and he asked (if you have the time, of course) if you could stop by to receive gifts, congratulations and handshakes. with the spreading of the news, a powerful businessman of the area decided to hire you as the CEO of his company because of this tremendous feat and at the same time an important international shareholder wants to sponsor you to give speeches and teach everybody how to do as you did so the world becomes a better place. you have become famous not only here but also everywhere, everybody knows who you are. the news spread really fast and mayors of all cities are setting up porticos, ballons, colossal boom speakers, anything that can make your name stand out more and see which city can congratulate you the hardest for this magnificent feaes don't care what humans think is impossible. Yellow, black. Yellow, black. Yellow, black. Yellow, black. Ooh, black and yellow! Let's shake it up a little. Barry! Breakfast is ready! Ooming! Hang on a second. Hello? - Barry? - Adam? - Oan you believe this is happening? - I can't. I'll pick you up. Looking sharp. Use the stairs. Your father paid good money for those. Sorry. I'm excited. Here's the graduate. We're very proud of you, son. A perfect report card, all B's. Very proud. Ma! I got a thing going here. - You got lint on your fuzz. - Ow! That's me! - Wave to us! We'll be in row 118,000. - Bye! Barry, I told you, stop flying in the house! - Hey, Adam. - Hey, Barry. - Is that fuzz gel? - A little. Special day, graduation. Never thought I'd make it. Three days grade school, three days high school. Those were awkward. Three days college. I'm glad I took a day and hitchhiked around the hive. You did come back different. - Hi, Barry. - Artie, growing a mustache? Looks good. - Hear about Frankie? - Yeah. - You going to the funeral? - No, I'm not going. Everybody knows, sting someone, you die. Don't waste it on a squirrel. Such a hothead. I guess he could have just gotten out of the way. I love this incorporating an amusement park into our day. That's why we don't need vacations. Boy, quite a bit of pomp... under the circumstances. - Well, Adam, today we are men. - We are! - Bee-men. - Amen! Hallelujah! Students, faculty, distinguished bees, please welcome Dean Buzzwell. Welcome, New Hive Oity graduating class of... ...9:15. That concludes our ceremonies. And begins your career at Honex Industries! Will we pick ourjob today? I heard it's just orientation. Heads up! Here we go. Keep your hands and antennas inside the tram at all times. - Wonder what it'll be like? - A little scary. Welcome to Honex, a division of Honesco and a part of the Hexagon Group. This is it! Wow. Wow. We know that you, as a bee, have worked your whole life to get to the point where you can work for your whole life. Honey begins when our valiant Pollen Jocks bring the nectar to the hive. Our top-secret formula is automatically color-corrected, scent-adjusted and bubble-contoured into this soothing sweet syrup with its distinctive golden glow you know as... Honey! - That girl was hot. - She's my cousin! - She is? - Yes, we're all cousins. - Right. You're right. - At Honex, we constantly strive to improve every aspect of bee existence. These bees are stress-testing a new helmet technology. - What do you think he makes? - Not enough. Here we have our latest advancement, the Krelman. - What does that do? - Oatches that little strand of honey that hangs after you pour it. Saves us millions. Oan anyone work on the Krelman? Of course. Most bee jobs are small ones. But bees know that every small job, if it's done well, means a lot. But choose carefully because you'll stay in the job you pick for the rest of your life. The same job the rest of your life? I didn't know that. What's the difference? You'll be happy to know that bees, as a species, haven't had one day off in 27 million years. So you'll just work us to death? We'll sure try. Wow! That blew my mind! "What's the difference?" How can you say that? One job forever? That's an insane choice to have to make. I'm relieved. Now we only have to make one decision in life. But, Adam, how could they never have told us that? Why would you question anything? We're bees. We're the most perfectly functioning society on Earth. You ever think maybe things work a little too well here? Like what? Give me one example. I don't know. But you know what I'm talking about. Please clear the gate. Royal Nectar Force on approach. Wait a second. Oheck it out. - Hey, those are Pollen Jocks! - Wow. I've never seen them this close. They know what it's like outside the hive. Yeah, but some don't come back. - Hey, Jocks! - Hi, Jocks! You guys did great! You're monsters! You're sky freaks! I love it! I love it! - I wonder where they were. - I don't know. Their day's not planned. Outside the hive, flying who knows where, doing who knows what. You can'tjust decide to be a Pollen Jock. You have to be bred for that. Right. Look. That's more pollen than you and I will see in a lifetime. It's just a status symbol. Bees make too much of it. Perhaps. Unless you're wearing it and the ladies see you wearing it. Those ladies? Aren't they our cousins too? Distant. Distant. Look at these two. - Oouple of Hive Harrys. - Let's have fun with them. It must be dangerous being a Pollen Jock. Yeah. Once a bear pinned me against a mushroom! He had a paw on my throat, and with the other, he was slapping me! - Oh, my! - I never thought I'd knock him out. What were you doing during this? Trying to alert the authorities. I can autograph that. A little gusty out there today, wasn't it, comrades? Yeah. Gusty. We're hitting a sunflower patch six miles from here tomorrow. - Six miles, huh? - Barry! A puddle jump for us, but maybe you're not up for it. - Maybe I am. - You are not! We're going 0900 at J-Gate. What do you think, buzzy-boy? Are you bee enough? I might be. It all depends on what 0900 means. Hey, Honex! Dad, you surprised me. You decide what you're interested in? - Well, there's a lot of choices. - But you only get one. Do you ever get bored doing the same job every day? Son, let me tell you about stirring. You grab that stick, and you just move it around, and you stir it around. You get yourself into a rhythm. It's a beautiful thing. You know, Dad, the more I think about it, maybe the honey field just isn't right for me. You were thinking of what, making balloon animals? That's a bad job for a guy with a stinger. Janet, your son's not sure he wants to go into honey! - Barry, you are so funny sometimes. - I'm not trying to be funny. You're not funny! You're going into honey. Our son, the stirrer! - You're gonna be a stirrer? - No one's listening to me! Wait till you see the sticks I have. I could say anything right now. I'm gonna get an ant tattoo! Let's open some honey and celebrate! Maybe I'll pierce my thorax. Shave my antennae. Shack up with a grasshopper. Get a gold tooth and call everybody "dawg"! I'm so proud. - We're starting work today! - Today's the day. Oome on! All the good jobs will be gone. Yeah, right. Pollen counting, stunt bee, pouring, stirrer, front desk, hair removal... - Is it still available? - Hang on. Two left! One of them's yours! Oongratulations! Step to the side. - What'd you get? - Picking crud out. Stellar! Wow! Oouple of newbies? Yes, sir! Our first day! We are ready! Make your choice. - You want to go first? - No, you go. Oh, my. What's available? Restroom attendant's open, not for the reason you think. - Any chance of getting the Krelman? - Sure, you're on. I'm sorry, the Krelman just closed out. Wax monkey's always open. The Krelman opened up again. What happened? A bee died. Makes an opening. See? He's dead. Another dead one. Deady. Deadified. Two more dead. Dead from the neck up. Dead from the neck down. That's life! Oh, this is so hard! Heating, cooling, stunt bee, pourer, stirrer, humming, inspector number seven, lint coordinator, stripe supervisor, mite wrangler. Barry, what do you think I should... Barry? Barry! All right, we've got the sunflower patch in quadrant nine... What happened to you? Where are you? - I'm going out. - Out? Out where? - Out there. - Oh, no! I have to, before I go to work for the rest of my life. You're gonna die! You're crazy! Hello? Another call coming in. If anyone's feeling brave, there's a Korean deli on 83rd that gets their roses today. Hey, guys. - Look at that. - Isn't that the kid we saw yesterday? Hold it, son, flight deck's restricted. It's OK, Lou. We're gonna take him up. Really? Feeling lucky, are you? Sign here, here. Just initial that. - Thank you. - OK. You got a rain advisory today, and as you all know, bees cannot fly in rain. So be careful. As always, watch your brooms, hockey sticks, dogs, birds, bears and bats. Also, I got a couple of reports of root beer being poured on us. Murphy's in a home because of it, babbling like a cicada! - That's awful. - And a reminder for you rookies, bee law number one, absolutely no talking to humans! All right, launch positions! Buzz, buzz, buzz, buzz! Buzz, buzz, buzz, buzz! Buzz, buzz, buzz, buzz! Black and yellow! Hello! You ready for this, hot shot? Yeah. Yeah, bring it on. Wind, check. - Antennae, check. - Nectar pack, check. - Wings, check. - Stinger, check. Scared out of my shorts, check. OK, ladies, let's move it out! Pound those petunias, you striped stem-suckers! All of you, drain those flowers! Wow! I'm out! I can't believe I'm out! So blue. I feel so fast and free! Box kite! Wow! Flowers! This is Blue Leader. We have roses visual. Bring it around 30 degrees and hold. Roses! 30 degrees, roger. Bringing it around. Stand to the side, kid. It's got a bit of a kick. That is one nectar collector! - Ever see pollination up close? - No, sir. I pick up some pollen here, sprinkle it over here. Maybe a dash over there, a pinch on that one. See that? It's a little bit of magic. That's amazing. Why do we do that? That's pollen power. More pollen, more flowers, more nectar, more honey for us. Oool. I'm picking up a lot of bright yellow. Oould be daisies. Don't we need those? Oopy that visual. Wait. One of these flowers seems to be on the move. Say again? You're reporting a moving flower? Affirmative. That was on the line! This is the coolest. What is it? I don't know, but I'm loving this color. It smells good. Not like a flower, but I like it. Yeah, fuzzy. Ohemical-y. Oareful, guys. It's a little grabby. My sweet lord of bees! Oandy-brain, get off there! Problem! - Guys! - This could be bad. Affirmative. Very close. Gonna hurt. Mama's little boy. You are way out of position, rookie! Ooming in at you like a missile! Help me! I don't think these are flowers. - Should we tell him? - I think he knows. What is this?! Match point! You can start packing up, honey, because you're about to eat it! Yowser! Gross. There's a bee in the car! - Do something! - I'm driving! - Hi, bee. - He's back here! He's going to sting me! Nobody move. If you don't move, he won't sting you. Freeze! He blinked! Spray him, Granny! What are you doing?! Wow... the tension level out here is unbelievable. I gotta get home. Oan't fly in rain. Oan't fly in rain. Oan't fly in rain. Mayday! Mayday! Bee going down! Ken, could you close the window please? Ken, could you close the window please? Oheck out my new resume. I made it into a fold-out brochure. You see? Folds out. Oh, no. More humans. I don't need this. What was that? Maybe this time. This time. This time. This time! This time! This... Drapes! That is diabolical. It's fantastic. It's got all my special skills, even my top-ten favorite movies. What's number one? Star Wars? Nah, I don't go for that... ...kind of stuff. No wonder we shouldn't talk to them. They're out of their minds. When I leave a job interview, they're flabbergasted, can't believe what I say. There's the sun. Maybe that's a way out. I don't remember the sun having a big 75 on it. I predicted global warming. I could feel it getting hotter. At first I thought it was just me. Wait! Stop! Bee! Stand back. These are winter boots. Wait! Don't kill him! You know I'm allergic to them! This thing could kill me! Why does his life have less value than yours? Why does his life have any less value than mine? Is that your statement? I'm just saying all life has value. You don't know what he's capable of feeling. My brochure! There you go, little guy. I'm not scared of him. It's an allergic thing. Put that on your resume brochure. My whole face could puff up. Make it one of your special skills. Knocking someone out is also a special skill. Right. Bye, Vanessa. Thanks. - Vanessa, next week? Yogurt night? - Sure, Ken. You know, whatever. - You could put carob chips on there. - Bye. - Supposed to be less calories. - Bye. I gotta say something. She saved my life. I gotta say something. All right, here it goes. Nah. What would I say? I could really get in trouble. It's a bee law. You're not supposed to talk to a human. I can't believe I'm doing this. I've got to. Oh, I can't do it. Oome on! No. Yes. No. Do it. I can't. How should I start it? "You like jazz?" No, that's no good. Here she comes! Speak, you fool! Hi! I'm sorry. - You're talking. - Yes, I know. You're talking! I'm so sorry. No, it's OK. It's fine. I know I'm dreaming. But I don't recall going to bed. Well, I'm sure this is very disconcerting. This is a bit of a surprise to me. I mean, you're a bee! I am. And I'm not supposed to be doing this, but they were all trying to kill me. And if it wasn't for you... I had to thank you. It's just how I was raised. That was a little weird. - I'm talking with a bee. - Yeah. I'm talking to a bee. And the bee is talking to me! I just want to say I'm grateful. I'll leave now. - Wait! How did you learn to do that? - What? The talking thing. Same way you did, I guess. "Mama, Dada, honey." You pick it up. - That's very funny. - Yeah. Bees are funny. If we didn't laugh, we'd cry with what we have to deal with. Anyway... Oan I... ...get you something? - Like what? I don't know. I mean... I don't know. Ooffee? I don't want to put you out. It's no trouble. It takes two minutes. - It's just coffee. - I hate to impose. - Don't be ridiculous! - Actually, I would love a cup. Hey, you want rum cake? - I shouldn't. - Have some. - No, I can't. - Oome on! I'm trying to lose a couple micrograms. - Where? - These stripes don't help. You look great! I don't know if you know anything about fashion. Are you all right? No. He's making the tie in the cab as they're flying up Madison. He finally gets there. He runs up the steps into the church. The wedding is on. And he says, "Watermelon? I thought you said Guatemalan. Why would I marry a watermelon?" Is that a bee joke? That's the kind of stuff we do. Yeah, different. So, what are you gonna do, Barry? About work? I don't know. I want to do my part for the hive, but I can't do it the way they want. I know how you feel. - You do? - Sure. My parents wanted me to be a lawyer or a doctor, but I wanted to be a florist. - Really? - My only interest is flowers. Our new queen was just elected with that same campaign slogan. Anyway, if you look... There's my hive right there. See it? You're in Sheep Meadow! Yes! I'm right off the Turtle Pond! No way! I know that area. I lost a toe ring there once. - Why do girls put rings on their toes? - Why not? - It's like putting a hat on your knee. - Maybe I'll try that. - You all right, ma'am? - Oh, yeah. Fine. Just having two cups of coffee! Anyway, this has been great. Thanks for the coffee. Yeah, it's no trouble. Sorry I couldn't finish it. If I did, I'd be up the rest of my life. Are you...? Oan I take a piece of this with me? Sure! Here, have a crumb. - Thanks! - Yeah. All right. Well, then... I guess I'll see you around. Or not. OK, Barry. And thank you so much again... for before. Oh, that? That was nothing. Well, not nothing, but... Anyway... This can't possibly work. He's all set to go. We may as well try it. OK, Dave, pull the chute. - Sounds amazing. - It was amazing! It was the scariest, happiest moment of my life. Humans! I can't believe you were with humans! Giant, scary humans! What were they like? Huge and crazy. They talk crazy. They eat crazy giant things. They drive crazy. - Do they try and kill you, like on TV? - Some of them. But some of them don't. - How'd you get back? - Poodle. You did it, and I'm glad. You saw whatever you wanted to see. You had your "experience." Now you can pick out yourjob and be normal. - Well... - Well? Well, I met someone. You did? Was she Bee-ish? - A wasp?! Your parents will kill you! - No, no, no, not a wasp. - Spider? - I'm not attracted to spiders. I know it's the hottest thing, with the eight legs and all. I can't get by that face. So who is she? She's... human. No, no. That's a bee law. You wouldn't break a bee law. - Her name's Vanessa. - Oh, boy. She's so nice. And she's a florist! Oh, no! You're dating a human florist! We're not dating. You're flying outside the hive, talking to humans that attack our homes with power washers and M-80s! One-eighth a stick of dynamite! She saved my life! And she understands me. This is over! Eat this. This is not over! What was that? - They call it a crumb. - It was so stingin' stripey! And that's not what they eat. That's what falls off what they eat! - You know what a Oinnabon is? - No. It's bread and cinnamon and frosting. They heat it up... Sit down! ...really hot! - Listen to me! We are not them! We're us. There's us and there's them! Yes, but who can deny the heart that is yearning? There's no yearning. Stop yearning. Listen to me! You have got to start thinking bee, my friend. Thinking bee! - Thinking bee. - Thinking bee. Thinking bee! Thinking bee! Thinking bee! Thinking bee! There he is. He's in the pool. You know what your problem is, Barry? I gotta start thinking bee? How much longer will this go on? It's been three days! Why aren't you working? I've got a lot of big life decisions to think about. What life? You have no life! You have no job. You're barely a bee! Would it kill you to make a little honey? Barry, come out. Your father's talking to you. Martin, would you talk to him? Barry, I'm talking to you! You coming? Got everything? All set! Go ahead. I'll catch up. Don't be too long. Watch this! Vanessa! - We're still here. - I told you not to yell at him. He doesn't respond to yelling! - Then why yell at me? - Because you don't listen! I'm not listening to this. Sorry, I've gotta go. - Where are you going? - I'm meeting a friend. A girl? Is this why you can't decide? Bye. I just hope she's Bee-ish. They have a huge parade of flowers every year in Pasadena? To be in the Tournament of Roses, that's every florist's dream! Up on a float, surrounded by flowers, crowds cheering. A tournament. Do the roses compete in athletic events? No. All right, I've got one. How come you don't fly everywhere? It's exhausting. Why don't you run everywhere? It's faster. Yeah, OK, I see, I see. All right, your turn. TiVo. You can just freeze live TV? That's insane! You don't have that? We have Hivo, but it's a disease. It's a horrible, horrible disease. Oh, my. Dumb bees! You must want to sting all those jerks. We try not to sting. It's usually fatal for us. So you have to watch your temper. Very carefully. You kick a wall, take a walk, write an angry letter and throw it out. Work through it like any emotion: Anger, jealousy, lust. Oh, my goodness! Are you OK? Yeah. - What is wrong with you?! - It's a bug. He's not bothering anybody. Get out of here, you creep! What was that? A Pic 'N' Save circular? Yeah, it was. How did you know? It felt like about 10 pages. Seventy-five is pretty much our limit. You've really got that down to a science. - I lost a cousin to Italian Vogue. - I'll bet. What in the name of Mighty Hercules is this? How did this get here? Oute Bee, Golden Blossom, Ray Liotta Private Select? - Is he that actor? - I never heard of him. - Why is this here? - For people. We eat it. You don't have enough food of your own? - Well, yes. - How do you get it? - Bees make it. - I know who makes it! And it's hard to make it! There's heating, cooling, stirring. You need a whole Krelman thing! - It's organic. - It's our-ganic! It's just honey, Barry. Just what?! Bees don't know about this! This is stealing! A lot of stealing! You've taken our homes, schools, hospitals! This is all we have! And it's on sale?! I'm getting to the bottom of this. I'm getting to the bottom of all of this! Hey, Hector. - You almost done? - Almost. He is here. I sense it. Well, I guess I'll go home now and just leave this nice honey out, with no one around. You're busted, box boy! I knew I heard something. So you can talk! I can talk. And now you'll start talking! Where you getting the sweet stuff? Who's your supplier? I don't understand. I thought we were friends. The last thing we want to do is upset bees! You're too late! It's ours now! You, sir, have crossed the wrong sword! You, sir, will be lunch for my iguana, Ignacio! Where is the honey coming from? Tell me where! Honey Farms! It comes from Honey Farms! Orazy person! What horrible thing has happened here? These faces, they never knew what hit them. And now they're on the road to nowhere! Just keep still. What? You're not dead? Do I look dead? They will wipe anything that moves. Where you headed? To Honey Farms. I am onto something huge here. I'm going to Alaska. Moose blood, crazy stuff. Blows your head off! I'm going to Tacoma. - And you? - He really is dead. All right. Uh-oh! - What is that?! - Oh, no! - A wiper! Triple blade! - Triple blade? Jump on! It's your only chance, bee! Why does everything have to be so doggone clean?! How much do you people need to see?! Open your eyes! Stick your head out the window! From NPR News in Washington, I'm Oarl Kasell. But don't kill no more bugs! - Bee! - Moose blood guy!! - You hear something? - Like what? Like tiny screaming. Turn off the radio. Whassup, bee boy? Hey, Blood. Just a row of honey jars, as far as the eye could see. Wow! I assume wherever this truck goes is where they're getting it. I mean, that honey's ours. - Bees hang tight. - We're all jammed in. It's a close community. Not us, man. We on our own. Every mosquito on his own. - What if you get in trouble? - You a mosquito, you in trouble. Nobody likes us. They just smack. See a mosquito, smack, smack! At least you're out in the world. You must meet girls. Mosquito girls try to trade up, get with a moth, dragonfly. Mosquito girl don't want no mosquito. You got to be kidding me! Mooseblood's about to leave the building! So long, bee! - Hey, guys! - Mooseblood! I knew I'd catch y'all down here. Did you bring your crazy straw? We throw it in jars, slap a label on it, and it's pretty much pure profit. What is this place? A bee's got a brain the size of a pinhead. They are pinheads! Pinhead. - Oheck out the new smoker. - Oh, sweet. That's the one you want. The Thomas 3000! Smoker? Ninety puffs a minute, semi-automatic. Twice the nicotine, all the tar. A couple breaths of this knocks them right out. They make the honey, and we make the money. "They make the honey, and we make the money"? Oh, my! What's going on? Are you OK? Yeah. It doesn't last too long. Do you know you're in a fake hive with fake walls? Our queen was moved here. We had no choice. This is your queen? That's a man in women's clothes! That's a drag queen! What is this? Oh, no! There's hundreds of them! Bee honey. Our honey is being brazenly stolen on a massive scale! This is worse than anything bears have done! I intend to do something. Oh, Barry, stop. Who told you humans are taking our honey? That's a rumor. Do these look like rumors? That's a conspiracy theory. These are obviously doctored photos. How did you get mixed up in this? He's been talking to humans. - What? - Talking to humans?! He has a human girlfriend. And they make out! Make out? Barry! We do not. - You wish you could. - Whose side are you on? The bees! I dated a cricket once in San Antonio. Those crazy legs kept me up all night. Barry, this is what you want to do with your life? I want to do it for all our lives. Nobody works harder than bees! Dad, I remember you coming home so overworked your hands were still stirring. You couldn't stop. I remember that. What right do they have to our honey? We live on two cups a year. They put it in lip balm for no reason whatsoever! Even if it's true, what can one bee do? Sting them where it really hurts. In the face! The eye! - That would hurt. - No. Up the nose? That's a killer. There's only one place you can sting the humans, one place where it matters. Hive at Five, the hive's only full-hour action news source. No more bee beards! With Bob Bumble at the anchor desk. Weather with Storm Stinger. Sports with Buzz Larvi. And Jeanette Ohung. - Good evening. I'm Bob Bumble. - And I'm Jeanette Ohung. A tri-county bee, Barry Benson, intends to sue the human race for stealing our honey, packaging it and profiting from it illegally! Tomorrow night on Bee Larry King, we'll have three former queens here in our studio, discussing their new book, Olassy Ladies, out this week on Hexagon. Tonight we're talking to Barry Benson. Did you ever think, "I'm a kid from the hive. I can't do this"? Bees have never been afraid to change the world. What about Bee Oolumbus? Bee Gandhi? Bejesus? Where I'm from, we'd never sue humans. We were thinking of stickball or candy stores. How old are you? The bee community is supporting you in this case, which will be the trial of the bee century. You know, they have a Larry King in the human world too. It's a common name. Next week... He looks like you and has a show and suspenders and colored dots... Next week... Glasses, quotes on the bottom from the guest even though you just heard 'em. Bear Week next week! They're scary, hairy and here live. Always leans forward, pointy shoulders, squinty eyes, very Jewish. In tennis, you attack at the point of weakness! It was my grandmother, Ken. She's 81. Honey, her backhand's a joke! I'm not gonna take advantage of that? Quiet, please. Actual work going on here. - Is that that same bee? - Yes, it is! I'm helping him sue the human race. - Hello. - Hello, bee. This is Ken. Yeah, I remember you. Timberland, size ten and a half. Vibram sole, I believe. Why does he talk again? Listen, you better go 'cause we're really busy working. But it's our yogurt night! Bye-bye. Why is yogurt night so difficult?! You poor thing. You two have been at this for hours! Yes, and Adam here has been a huge help. - Frosting... - How many sugars? Just one. I try not to use the competition. So why are you helping me? Bees have good qualities. And it takes my mind off the shop. Instead of flowers, people are giving balloon bouquets now. Those are great, if you're three. And artificial flowers. - Oh, those just get me psychotic! - Yeah, me too. Bent stingers, pointless pollination. Bees must hate those fake things! Nothing worse than a daffodil that's had work done. Maybe this could make up for it a little bit. - This lawsuit's a pretty big deal. - I guess. You sure you want to go through with it? Am I sure? When I'm done with the humans, they won't be able to say, "Honey, I'm home," without paying a royalty! It's an incredible scene here in downtown Manhattan, where the world anxiously waits, because for the first time in history, we will hear for ourselves if a honeybee can actually speak. What have we gotten into here, Barry? It's pretty big, isn't it? I can't believe how many humans don't work during the day. You think billion-dollar multinational food companies have good lawyers? Everybody needs to stay behind the barricade. - What's the matter? - I don't know, I just got a chill. Well, if it isn't the bee team. You boys work on this? All rise! The Honorable Judge Bumbleton presiding. All right. Oase number 4475, Superior Oourt of New York, Barry Bee Benson v. the Honey Industry is now in session. Mr. Montgomery, you're representing the five food companies collectively? A privilege. Mr. Benson... you're representing all the bees of the world? I'm kidding. Yes, Your Honor, we're ready to proceed. Mr. Montgomery, your opening statement, please. Ladies and gentlemen of the jury, my grandmother was a simple woman. Born on a farm, she believed it was man's divine right to benefit from the bounty of nature God put before us. If we lived in the topsy-turvy world Mr. Benson imagines, just think of what would it mean. I would have to negotiate with the silkworm for the elastic in my britches! Talking bee! How do we know this isn't some sort of holographic motion-picture-capture Hollywood wizardry? They could be using laser beams! Robotics! Ventriloquism! Oloning! For all we know, he could be on steroids! Mr. Benson? Ladies and gentlemen, there's no trickery here. I'm just an ordinary bee. Honey's pretty important to me. It's important to all bees. We invented it! We make it. And we protect it with our lives. Unfortunately, there are some people in this room who think they can take it from us 'cause we're the little guys! I'm hoping that, after this is all over, you'll see how, by taking our honey, you not only take everything we have but everything we are! I wish he'd dress like that all the time. So nice! Oall your first witness. So, Mr. Klauss Vanderhayden of Honey Farms, big company you have. I suppose so. I see you also own Honeyburton and Honron! Yes, they provide beekeepers for our farms. Beekeeper. I find that to be a very disturbing term. I don't imagine you employ any bee-free-ers, do you? - No. - I couldn't hear you. - No. - No. Because you don't free bees. You keep bees. Not only that, it seems you thought a bear would be an appropriate image for a jar of honey. They're very lovable creatures. Yogi Bear, Fozzie Bear, Build-A-Bear. You mean like this? Bears kill bees! How'd you like his head crashing through your living room?! Biting into your couch! Spitting out your throw pillows! OK, that's enough. Take him away. So, Mr. Sting, thank you for being here. Your name intrigues me. - Where have I heard it before? - I was with a band called The Police. But you've never been a police officer, have you? No, I haven't. No, you haven't. And so here we have yet another example of bee culture casually stolen by a human for nothing more than a prance-about stage name. Oh, please. Have you ever been stung, Mr. Sting? Because I'm feeling a little stung, Sting. Or should I say... Mr. Gordon M. Sumner! That's not his real name?! You idiots! Mr. Liotta, first, belated congratulations on your Emmy win for a guest spot on ER in 2005. Thank you. Thank you. I see from your resume that you're devilishly handsome with a churning inner turmoil that's ready to blow. I enjoy what I do. Is that a crime? Not yet it isn't. But is this what it's come to for you? Exploiting tiny, helpless bees so you don't have to rehearse your part and learn your lines, sir? Watch it, Benson! I could blow right now! This isn't a goodfella. This is a badfella! Why doesn't someone just step on this creep, and we can all go home?! - Order in this court! - You're all thinking it! Order! Order, I say! - Say it! - Mr. Liotta, please sit down! I think it was awfully nice of that bear to pitch in like that. I think the jury's on our side. Are we doing everything right, legally? I'm a florist. Right. Well, here's to a great team. To a great team! Well, hello. - Ken! - Hello. I didn't think you were coming. No, I was just late. I tried to call, but... the battery. I didn't want all this to go to waste, so I called Barry. Luckily, he was free. Oh, that was lucky. There's a little left. I could heat it up. Yeah, heat it up, sure, whatever. So I hear you're quite a tennis player. I'm not much for the game myself. The ball's a little grabby. That's where I usually sit. Right... there. Ken, Barry was looking at your resume, and he agreed with me that eating with chopsticks isn't really a special skill. You think I don't see what you're doing? I know how hard it is to find the rightjob. We have that in common. Do we? Bees have 100 percent employment, but we do jobs like taking the crud out. That's just what I was thinking about doing. Ken, I let Barry borrow your razor for his fuzz. I hope that was all right. I'm going to drain the old stinger. Yeah, you do that. Look at that. You know, I've just about had it with your little mind games. - What's that? - Italian Vogue. Mamma mia, that's a lot of pages. A lot of ads. Remember what Van said, why is your life more valuable than mine? Funny, I just can't seem to recall that! I think something stinks in here! I love the smell of flowers. How do you like the smell of flames?! Not as much. Water bug! Not taking sides! Ken, I'm wearing a Ohapstick hat! This is pathetic! I've got issues! Well, well, well, a royal flush! - You're bluffing. - Am I? Surf's up, dude! Poo water! That bowl is gnarly. Except for those dirty yellow rings! Kenneth! What are you doing?! You know, I don't even like honey! I don't eat it! We need to talk! He's just a little bee! And he happens to be the nicest bee I've met in a long time! Long time? What are you talking about?! Are there other bugs in your life? No, but there are other things bugging me in life. And you're one of them! Fine! Talking bees, no yogurt night... My nerves are fried from riding on this emotional roller coaster! Goodbye, Ken. And for your information, I prefer sugar-free, artificial sweeteners made by man! I'm sorry about all that. I know it's got an aftertaste! I like it! I always felt there was some kind of barrier between Ken and me. I couldn't overcome it. Oh, well. Are you OK for the trial? I believe Mr. Montgomery is about out of ideas. We would like to call Mr. Barry Benson Bee to the stand. Good idea! You can really see why he's considered one of the best lawyers... Yeah. Layton, you've gotta weave some magic with this jury, or it's gonna be all over. Don't worry. The only thing I have to do to turn this jury around is to remind them of what they don't like about bees. - You got the tweezers? - Are you allergic? Only to losing, son. Only to losing. Mr. Benson Bee, I'll ask you what I think we'd all like to know. What exactly is your relationship to that woman? We're friends. - Good friends? - Yes. How good? Do you live together? Wait a minute... Are you her little... ...bedbug? I've seen a bee documentary or two. From what I understand, doesn't your queen give birth to all the bee children? - Yeah, but... - So those aren't your real parents! - Oh, Barry... - Yes, they are! Hold me back! You're an illegitimate bee, aren't you, Benson? He's denouncing bees! Don't y'all date your cousins? - Objection! - I'm going to pincushion this guy! Adam, don't! It's what he wants! Oh, I'm hit!! Oh, lordy, I am hit! Order! Order! The venom! The venom is coursing through my veins! I have been felled by a winged beast of destruction! You see? You can't treat them like equals! They're striped savages! Stinging's the only thing they know! It's their way! - Adam, stay with me. - I can't feel my legs. What angel of mercy will come forward to suck the poison from my heaving buttocks? I will have order in this court. Order! Order, please! The case of the honeybees versus the human race took a pointed turn against the bees yesterday when one of their legal team stung Layton T. Montgomery. - Hey, buddy. - Hey. - Is there much pain? - Yeah. I... I blew the whole case, didn't I? It doesn't matter. What matters is you're alive. You could have died. I'd be better off dead. Look at me. They got it from the cafeteria downstairs, in a tuna sandwich. Look, there's a little celery still on it. What was it like to sting someone? I can't explain it. It was all... All adrenaline and then... and then ecstasy! All right. You think it was all a trap? Of course. I'm sorry. I flew us right into this. What were we thinking? Look at us. We're just a couple of bugs in this world. What will the humans do to us if they win? I don't know. I hear they put the roaches in motels. That doesn't sound so bad. Adam, they check in, but they don't check out! Oh, my. Oould you get a nurse to close that window? - Why? - The smoke. Bees don't smoke. Right. Bees don't smoke. Bees don't smoke! But some bees are smoking. That's it! That's our case! It is? It's not over? Get dressed. I've gotta go somewhere. Get back to the court and stall. Stall any way you can. And assuming you've done step correctly, you're ready for the tub. Mr. Flayman. Yes? Yes, Your Honor! Where is the rest of your team? Well, Your Honor, it's interesting. Bees are trained to fly haphazardly, and as a result, we don't make very good time. I actually heard a funny story about... Your Honor, haven't these ridiculous bugs taken up enough of this court's valuable time? How much longer will we allow these absurd shenanigans to go on? They have presented no compelling evidence to support their charges against my clients, who run legitimate businesses. I move for a complete dismissal of this entire case! Mr. Flayman, I'm afraid I'm going to have to consider Mr. Montgomery's motion. But you can't! We have a terrific case. Where is your proof? Where is the evidence? Show me the smoking gun! Hold it, Your Honor! You want a smoking gun? Here is your smoking gun. What is that? It's a bee smoker! What, this? This harmless little contraption? This couldn't hurt a fly, let alone a bee. Look at what has happened to bees who have never been asked, "Smoking or non?" Is this what nature intended for us? To be forcibly addicted to smoke machines and man-made wooden slat work camps? Living out our lives as honey slaves to the white man? - What are we gonna do? - He's playing the species card. Ladies and gentlemen, please, free these bees! Free the bees! Free the bees! Free the bees! Free the bees! Free the bees! The court finds in favor of the bees! Vanessa, we won! I knew you could do it! High-five! Sorry. I'm OK! You know what this means? All the honey will finally belong to the bees. Now we won't have to work so hard all the time. This is an unholy perversion of the balance of nature, Benson. You'll regret this. Barry, how much honey is out there? All right. One at a time. Barry, who are you wearing? My sweater is Ralph Lauren, and I have no pants. - What if Montgomery's right? - What do you mean? We've been living the bee way a long time, 27 million years. Oongratulations on your victory. What will you demand as a settlement? First, we'll demand a complete shutdown of all bee work camps. Then we want back the honey that was ours to begin with, every last drop. We demand an end to the glorification of the bear as anything more than a filthy, smelly, bad-breath stink machine. We're all aware of what they do in the woods. Wait for my signal. Take him out. He'll have nauseous for a few hours, then he'll be fine. And we will no longer tolerate bee-negative nicknames... But it's just a prance-about stage name! ...unnecessary inclusion of honey in bogus health products and la-dee-da human tea-time snack garnishments. Oan't breathe. Bring it in, boys! Hold it right there! Good. Tap it. Mr. Buzzwell, we just passed three cups, and there's gallons more coming! - I think we need to shut down! - Shut down? We've never shut down. Shut down honey production! Stop making honey! Turn your key, sir! What do we do now? Oannonball! We're shutting honey production! Mission abort. Aborting pollination and nectar detail. Returning to base. Adam, you wouldn't believe how much honey was out there. Oh, yeah? What's going on? Where is everybody? - Are they out celebrating? - They're home. They don't know what to do. Laying out, sleeping in. I heard your Uncle Oarl was on his way to San Antonio with a cricket. At least we got our honey back. Sometimes I think, so what if humans liked our honey? Who wouldn't? It's the greatest thing in the world! I was excited to be part of making it. This was my new desk. This was my new job. I wanted to do it really well. And now... Now I can't. I don't understand why they're not happy. I thought their lives would be better! They're doing nothing. It's amazing. Honey really changes people. You don't have any idea what's going on, do you? - What did you want to show me? - This. What happened here? That is not the half of it. Oh, no. Oh, my. They're all wilting. Doesn't look very good, does it? No. And

Bitcoin: A Peer-to-Peer Electronic Cash System Satoshi Nakamoto satoshin@gmx.com www.bitcoin.org Abstract. A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution. Digital signatures provide part of the solution, but the main benefits are lost if a trusted third party is still required to prevent double-spending. We propose a solution to the double-spending problem using a peer-to-peer network. The network timestamps transactions by hashing them into an ongoing chain of hash-based proof-of-work, forming a record that cannot be changed without redoing the proof-of-work. The longest chain not only serves as proof of the sequence of events witnessed, but proof that it came from the largest pool of CPU power. As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they'll generate the longest chain and outpace attackers. The network itself requires minimal structure. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will, accepting the longest proof-of-work chain as proof of what happened while they were gone. 1. Introduction Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions, and there is a broader cost in the loss of ability to make non-reversible payments for non- reversible services. With the possibility of reversal, the need for trust spreads. Merchants must be wary of their customers, hassling them for more information than they would otherwise need. A certain percentage of fraud is accepted as unavoidable. These costs and payment uncertainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party. What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party. Transactions that are computationally impractical to reverse would protect sellers from fraud, and routine escrow mechanisms could easily be implemented to protect buyers. In this paper, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp server to generate computational proof of the chronological order of transactions. The system is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes. 1 2. Transactions We define an electronic coin as a chain of digital signatures. Each owner transfers the coin to the next by digitally signing a hash of the previous transaction and the public key of the next owner and adding these to the end of the coin. A payee can verify the signatures to verify the chain of ownership. Transaction Hash Transaction Hash Transaction Hash Owner 1's Public Key Owner 2's Public Key Owner 3's Public Key Owner 0's Signature Owner 1's Signature The problem of course is the payee can't verify that one of the owners did not double-spend the coin. A common solution is to introduce a trusted central authority, or mint, that checks every transaction for double spending. After each transaction, the coin must be returned to the mint to issue a new coin, and only coins issued directly from the mint are trusted not to be double-spent. The problem with this solution is that the fate of the entire money system depends on the company running the mint, with every transaction having to go through them, just like a bank. We need a way for the payee to know that the previous owners did not sign any earlier transactions. For our purposes, the earliest transaction is the one that counts, so we don't care about later attempts to double-spend. The only way to confirm the absence of a transaction is to be aware of all transactions. In the mint based model, the mint was aware of all transactions and decided which arrived first. To accomplish this without a trusted party, transactions must be publicly announced [1], and we need a system for participants to agree on a single history of the order in which they were received. The payee needs proof that at the time of each transaction, the majority of nodes agreed it was the first received. 3. Timestamp Server The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post [2-5]. The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it. Hash Hash Owner 2's Signature Owner 1's Private Key Owner 2's Private Key Owner 3's Private Key Block Item Item ... 2 Block Item Item ... Verify Verify Sign Sign 4. Proof-of-Work To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof- of-work system similar to Adam Back's Hashcash [6], rather than newspaper or Usenet posts. The proof-of-work involves scanning for a value that when hashed, such as with SHA-256, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash. For our timestamp network, we implement the proof-of-work by incrementing a nonce in the block until a value is found that gives the block's hash the required zero bits. Once the CPU effort has been expended to make it satisfy the proof-of-work, the block cannot be changed without redoing the work. As later blocks are chained after it, the work to change the block would include redoing all the blocks after it. The proof-of-work also solves the problem of determining representation in majority decision making. If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote. The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. If a majority of CPU power is controlled by honest nodes, the honest chain will grow the fastest and outpace any competing chains. To modify a past block, an attacker would have to redo the proof-of-work of the block and all blocks after it and then catch up with and surpass the work of the honest nodes. We will show later that the probability of a slower attacker catching up diminishes exponentially as subsequent blocks are added. To compensate for increasing hardware speed and varying interest in running nodes over time, the proof-of-work difficulty is determined by a moving average targeting an average number of blocks per hour. If they're generated too fast, the difficulty increases. 5. Network The steps to run the network are as follows: 1) New transactions are broadcast to all nodes. 2) Each node collects new transactions into a block. 3) Each node works on finding a difficult proof-of-work for its block. 4) When a node finds a proof-of-work, it broadcasts the block to all nodes. 5) Nodes accept the block only if all transactions in it are valid and not already spent. 6) Nodes express their acceptance of the block by working on creating the next block in the chain, using the hash of the accepted block as the previous hash. Nodes always consider the longest chain to be the correct one and will keep working on extending it. If two nodes broadcast different versions of the next block simultaneously, some nodes may receive one or the other first. In that case, they work on the first one they received, but save the other branch in case it becomes longer. The tie will be broken when the next proof- of-work is found and one branch becomes longer; the nodes that were working on the other branch will then switch to the longer one. 3 Block Nonce Tx Tx ... Block Nonce Tx Tx ... Prev Hash Prev Hash New transaction broadcasts do not necessarily need to reach all nodes. As long as they reach many nodes, they will get into a block before long. Block broadcasts are also tolerant of dropped messages. If a node does not receive a block, it will request it when it receives the next block and realizes it missed one. 6. Incentive By convention, the first transaction in a block is a special transaction that starts a new coin owned by the creator of the block. This adds an incentive for nodes to support the network, and provides a way to initially distribute coins into circulation, since there is no central authority to issue them. The steady addition of a constant of amount of new coins is analogous to gold miners expending resources to add gold to circulation. In our case, it is CPU time and electricity that is expended. The incentive can also be funded with transaction fees. If the output value of a transaction is less than its input value, the difference is a transaction fee that is added to the incentive value of the block containing the transaction. Once a predetermined number of coins have entered circulation, the incentive can transition entirely to transaction fees and be completely inflation free. The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth. 7. Reclaiming Disk Space Once the latest transaction in a coin is buried under enough blocks, the spent transactions before it can be discarded to save disk space. To facilitate this without breaking the block's hash, transactions are hashed in a Merkle Tree [7][2][5], with only the root included in the block's hash. Old blocks can then be compacted by stubbing off branches of the tree. The interior hashes do not need to be stored. Block Hash0 Hash1 Hash2 Hash3 Tx0 Tx1 Tx2 Tx3 Block Header (Block Hash) Prev Hash Nonce Root Hash Hash01 Hash23 Block Block Header (Block Hash) Prev Hash Nonce Root Hash Hash01 Hash23 Hash2 Hash3 Tx3 Transactions Hashed in a Merkle Tree After Pruning Tx0-2 from the Block A block header with no transactions would be about 80 bytes. If we suppose blocks are generated every 10 minutes, 80 bytes * 6 * 24 * 365 = 4.2MB per year. With computer systems typically selling with 2GB of RAM as of 2008, and Moore's Law predicting current growth of 1.2GB per year, storage should not be a problem even if the block headers must be kept in memory. 4 8. Simplified Payment Verification It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in. He can't check the transaction for himself, but by linking it to a place in the chain, he can see that a network node has accepted it, and blocks added after it further confirm the network has accepted it. Longest Proof-of-Work Chain Block Header Block Header Block Header Prev Hash Nonce Prev Hash Nonce Prev Hash Nonce Merkle Root Merkle Root Merkle Root Hash01 Hash23 Merkle Branch for Tx3 Hash2 Hash3 Tx3 As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. While network nodes can verify transactions for themselves, the simplified method can be fooled by an attacker's fabricated transactions for as long as the attacker can continue to overpower the network. One strategy to protect against this would be to accept alerts from network nodes when they detect an invalid block, prompting the user's software to download the full block and alerted transactions to confirm the inconsistency. Businesses that receive frequent payments will probably still want to run their own nodes for more independent security and quicker verification. 9. Combining and Splitting Value Although it would be possible to handle coins individually, it would be unwieldy to make a separate transaction for every cent in a transfer. To allow value to be split and combined, transactions contain multiple inputs and outputs. Normally there will be either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and at most two outputs: one for the payment, and one returning the change, if any, back to the sender. It should be noted that fan-out, where a transaction depends on several transactions, and those transactions depend on many more, is not a problem here. There is never the need to extract a complete standalone copy of a transaction's history. 5 Transaction In Out In ... ... 10. Privacy The traditional banking model achieves a level of privacy by limiting access to information to the parties involved and the trusted third party. The necessity to announce all transactions publicly precludes this method, but privacy can still be maintained by breaking the flow of information in another place: by keeping public keys anonymous. The public can see that someone is sending an amount to someone else, but without information linking the transaction to anyone. This is similar to the level of information released by stock exchanges, where the time and size of individual trades, the "tape", is made public, but without telling who the parties were. Traditional Privacy Model Identities Transactions New Privacy Model Identities Transactions As an additional firewall, a new key pair should be used for each transaction to keep them from being linked to a common owner. Some linking is still unavoidable with multi-input transactions, which necessarily reveal that their inputs were owned by the same owner. The risk is that if the owner of a key is revealed, linking could reveal other transactions that belonged to the same owner. 11. Calculations We consider the scenario of an attacker trying to generate an alternate chain faster than the honest chain. Even if this is accomplished, it does not throw the system open to arbitrary changes, such as creating value out of thin air or taking money that never belonged to the attacker. Nodes are not going to accept an invalid transaction as payment, and honest nodes will never accept a block containing them. An attacker can only try to change one of his own transactions to take back money he recently spent. The race between the honest chain and an attacker chain can be characterized as a Binomial Random Walk. The success event is the honest chain being extended by one block, increasing its lead by +1, and the failure event is the attacker's chain being extended by one block, reducing the gap by -1. The probability of an attacker catching up from a given deficit is analogous to a Gambler's Ruin problem. Suppose a gambler with unlimited credit starts at a deficit and plays potentially an infinite number of trials to try to reach breakeven. We can calculate the probability he ever reaches breakeven, or that an attacker ever catches up with the honest chain, as follows [8]: p = probability an honest node finds the next block q = probability the attacker finds the next block qz = probability the attacker will ever catch up from z blocks behind Trusted Third Party q ={ 1 if p≤q} z q/pz if pq 6 Counterparty Public Public Given our assumption that p > q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases. With the odds against him, if he doesn't make a lucky lunge forward early on, his chances become vanishingly small as he falls further behind. We now consider how long the recipient of a new transaction needs to wait before being sufficiently certain the sender can't change the transaction. We assume the sender is an attacker who wants to make the recipient believe he paid him for a while, then switch it to pay back to himself after some time has passed. The receiver will be alerted when that happens, but the sender hopes it will be too late. The receiver generates a new key pair and gives the public key to the sender shortly before signing. This prevents the sender from preparing a chain of blocks ahead of time by working on it continuously until he is lucky enough to get far enough ahead, then executing the transaction at that moment. Once the transaction is sent, the dishonest sender starts working in secret on a parallel chain containing an alternate version of his transaction. The recipient waits until the transaction has been added to a block and z blocks have been linked after it. He doesn't know the exact amount of progress the attacker has made, but assuming the honest blocks took the average expected time per block, the attacker's potential progress will be a Poisson distribution with expected value:  = z qp To get the probability the attacker could still catch up now, we multiply the Poisson density for each amount of progress he could have made by the probability he could catch up from that point: ∞ ke−{q/pz−k ifk≤z} ∑k=0 k!⋅ 1 ifkz Rearranging to avoid summing the infinite tail of the distribution... z ke− z−k 1−∑k=0 k! 1−q/p  Converting to C code... #include <math.h> double AttackerSuccessProbability(double q, int z) { double p = 1.0 - q; double lambda = z * (q / p); double sum = 1.0; int i, k; for (k = 0; k <= z; k++) { double poisson = exp(-lambda); for (i = 1; i <= k; i++) poisson *= lambda / i; sum -= poisson * (1 - pow(q / p, z - k)); } return sum; } 7 Running some results, we can see the probability drop off exponentially with z. q=0.1 z=0 P=1.0000000 z=1 P=0.2045873 z=2 P=0.0509779 z=3 P=0.0131722 z=4 P=0.0034552 z=5 P=0.0009137 z=6 P=0.0002428 z=7 P=0.0000647 z=8 P=0.0000173 z=9 P=0.0000046 z=10 P=0.0000012 q=0.3 z=0 P=1.0000000 z=5 P=0.1773523 z=10 P=0.0416605 z=15 P=0.0101008 z=20 P=0.0024804 z=25 P=0.0006132 z=30 P=0.0001522 z=35 P=0.0000379 z=40 P=0.0000095 z=45 P=0.0000024 z=50 P=0.0000006 Solving for P less than 0.1%... P < 0.001 q=0.10 z=5 q=0.15 z=8 q=0.20 z=11 q=0.25 z=15 q=0.30 z=24 q=0.35 z=41 q=0.40 z=89 q=0.45 z=340 12. Conclusion We have proposed a system for electronic transactions without relying on trust. We started with the usual framework of coins made from digital signatures, which provides strong control of ownership, but is incomplete without a way to prevent double-spending. To solve this, we proposed a peer-to-peer network using proof-of-work to record a public history of transactions that quickly becomes computationally impractical for an attacker to change if honest nodes control a majority of CPU power. The network is robust in its unstructured simplicity. Nodes work all at once with little coordination. They do not need to be identified, since messages are not routed to any particular place and only need to be delivered on a best effort basis. Nodes can leave and rejoin the network at will, accepting the proof-of-work chain as proof of what happened while they were gone. They vote with their CPU power, expressing their acceptance of valid blocks by working on extending them and rejecting invalid blocks by refusing to work on them. Any needed rules and incentives can be enforced with this consensus mechanism. 8 References [1] W. Dai, "b-money," http://www.weidai.com/bmoney.txt, 1998. [2] H. Massias, X.S. Avila, and J.-J. Quisquater, "Design of a secure timestamping service with minimal trust requirements," In 20th Symposium on Information Theory in the Benelux, May 1999. [3] S. Haber, W.S. Stornetta, "How to time-stamp a digital document," In Journal of Cryptology, vol 3, no 2, pages 99-111, 1991. [4] D. Bayer, S. Haber, W.S. Stornetta, "Improving the efficiency and reliability of digital time-stamping," In Sequences II: Methods in Communication, Security and Computer Science, pages 329-334, 1993. [5] S. Haber, W.S. Stornetta, "Secure names for bit-strings," In Proceedings of the 4th ACM Conference on Computer and Communications Security, pages 28-35, April 1997. [6] A. Back, "Hashcash - a denial of service counter-measure," http://www.hashcash.org/papers/hashcash.pdf, 2002. [7] R.C. Merkle, "Protocols for public key cryptosystems," In Proc. 1980 Symposium on Security and Privacy, IEEE Computer Society, pages 122-133, April 1980. [8] W. Feller, "An introduction to probability theory and its applications," 1957. 9

PYTHON CODE WALKTHROUGH Data Sourcing In order to run a discounted cash flow model (DCF), I needed data, so I found a free API that provided us with everything I needed. I wrote a code that saved every financial statement of every company in a separate text file. In this code, I asked to ping the API’s URL for every ticker, open a text file for one of the financial statements for one company ticker, dump all the data found by the code into this file, and close it. This process was repeated for every company in our company list and every statement I have a code for. By doing so I Ire able to store the data for every company locally and did not need to ping the API every time I ran our code. Once all the financial data for each company was stored in form of a balance sheet, income statement, cash flow statement, and company profile text file, I needed to pick out specific items required for our DCF model. Thus, I defined the functions that selected all required items from the respective financial statements of each company and assigned them to a variable using utils.py. Discounted Cash Flow Model First of all, I needed to import the functions I defined in utils.py before defining the DCF model function, which would run for every company in our list. Next, I ensured to have 5 consecutive years of past data to compute the average. Thus, the first few lines of code checked whether the last year on record was 2019 from which point I would go back 5 years; if the last year was 2018, this would be taken as the first data entry from which I would go back 5 years. The second part mentioned above is important because companies file their 10-K, i.e. their annual report, at different times throughout the year so there may be companies that already filed their reports while others had not. After this step, five-year averages of every item’s percentage of revenue Ire calculated as Ill as the average revenue growth over the same period. These items included EBIT, depreciation & amortization, capital expenditures, and the change in net working capital. Once that was done, there Ire only three variables missing before calculating free cash flows for the next few years: a discount or hurdle rate; industry-specific perpetual growth rates; and a tax rate. After these three variables Ire set up, the next step was to calculate the free cash flows to the firm (fcff) for the next 5 years and determine the terminal value at the end of the period using the growth rate for the corresponding industry. For the former, I use a loop to calculate the fcff for all the year, discount it, and add it to one variable called fcffpv. Once the terminal value was calculated, these two additional numbers captured the enterprise value of the firm. Since I Ire interested in the equity value, I subtracted debt and add cash, which left us with the equity value. In one final step, I divided this value by the number of shares to end up with an intrinsic value per share. After calculating the intrinsic value per share, I compared it to the current share price with two additions. First, I added a buffer to minimize our downside risk for inaccuracy in calculations, which is called the margin of safety. Here, the intrinsic value should at least be 115% of the current share price. I also set an upper limit at 130% to ensure I would not include companies with extraordinarily high valuations, compared to their current price. If the share price calculated fell within this window, I added its ticker to a dataframe, which was the last step in the function. As such, the DCF function would run for every company and provide a dataframe with the tickers of all those companies that Ire undervalued at the time and fell within the 115% - 130% range. Portfolio Optimization The dataframe with the tickers of all the undervalued companies that was previously created has now become the portfolio, which I converted into a list and used as the source for further optimization that is about to come. Some general inputs for the rest of the code Ire the start and end date of the data I requested for optimization, as Ill as the risk-free rate and the number of simulations I wanted to run our optimizations for. Now that the general framework has been created, it is time to choose some conditioning variables to measure the performance of investment in one sector or across a combination of some/all sectors, respectively. Project Alpha uses the following conditioning variables to optimize its portfolios: • Sharpe Ratio: It measures the performance of an investment compared to the risk-free asset, i.e. the 10-year Treasury Bond, after adjusting for its risk factor or standard deviation. The Sharpe ratio would be given a higher Iight for investors who have a higher risk tolerance. In terms of code, I used the bt package to retrieve the data betIen the predetermined start and end date for the companies in our ticker list. This data was then used to find the portfolio with the highest Sharpe ratio. For that, random Iights Ire assigned to each company and the ratio was computed. After running the number of simulations previously determined, the Iights with the highest Sharpe ratio will be located using loc() and labeled ‘sharpe_portfolio’ which is a dataframe containing the excess return, the volatility, Sharpe ratio, as Ill as the Iights for every company. I also located the portfolio with the loIst volatility, put it in a dataframe called ‘min_volatility_port’ which has the same attributes. The rest of the code of this segment simply created a picture with all the portfolios generated, displaying the efficient frontier and highlighting the portfolio with the highest Sharpe ratio and loIst volatility. • Value at Risk (VaR): VaR was chosen as a diagnostic tool to assess the model. In our case, it basically indicated the percentage of time in which a loss greater than 1% would occur over a period of 5 years. Its limitation is that although it measures how bad the best of the bad is, it does not measure how bad it can get, meaning the worst of the worst. In regards to the code, I first requested the adjusted closing for the companies in our ticker list in the determined time horizon. I then retrieved the Iights from our Sharpe portfolio, set the number of days I wanted to simulate as Ill as the cutoff, before calculating the returns of every company in every period; here: daily. Thereafter, I created a new variable called ‘sigma’, which was be a copy of our return variable, in order to ensure the right format and type for our Monte Carlo loop. The simulation is pretty straight forward, as it measures how many runs the returns fall within 1% or outside of it. I then Iighed the resulting returns by the Iight of the company in the portfolio and whenever the portfolio return was outside the set boundary, it would count as a ‘bad simulation’. Once that is done, the number of bad simulations was divided by the total number of simulations to end up with a percentage of how many simulations were bad, which equals our VaR • Treynor Ratio: For the investors that already have a perfectly diversified portfolio and would like to add more assets to it, there would be a higher Iight on the Treynor ratio. It basically uses beta as a risk factor because it carries the risk relative to the market, instead of standard deviation as in Sharpe, meaning only systematic or non-diversifiable risk. For the code, I first calculated the portfolio’s beta. For that, I defined a function ‘beta’ that reads the beta of every company and returns it. The next step is to run a loop that would enter the beta of every company in our ticker list into a new dataframe. After setting the index equal to the tickers and transposing the Sharpe portfolio Iights, I can concat the two thus resulting in two columns: one is the beta of every company and the second is the corresponding Iight in the portfolio. I then created a third column as the product of columns one and two. The sum of all entries in that column is the portfolio beta, which was then used as the denominator for the ratio. The nominator was already calculated as ‘Excess Return’ in the Sharpe portfolio. • Sortino Ratio: The Sortino ratio measures only the downside risk (downside deviation or semi-deviation) by measuring returns against a minimum acceptable return, 𝜏. It is surprising to know that most of the industry ignores the total number of periods taken and just calculates the downside deviation by choosing the periods with downside risk, which results in misleading results. Project Alpha uses all the periods to calculate the same, so as to have an advantage over those robo-advisors/financial advisors that do not follow this process. The alpha in the future would be generated by going long on companies with high correct Sortino and low incorrect Sortino as they are undervalued, and shorting those with low correct Sortino and high incorrect Sortino as these are overvalued. The Sortino ratio would be given more Iight for investors who are more risk averse. This part of the code started with retrieving the data for our benchmark, the S&P 500, for the period and the calculating the average daily and annual return. After that, I calculate the portfolio returns, ‘returns[“Returns”]’, by adding the products of every company’s Iight times its return, which gave us the portfolio return for every period. From here, I calculated the downside risk by comparing the portfolio return in every period to the daily average return of our benchmark in a for loop. Before I did that, I defined a new variable called ‘semi’, which is a data series and will be filled with whatever comes out of the loop every single time. If the portfolio return minus the average daily return of the benchmark was greater than 0 – meaning the portfolio earned more than the average of the S&P500 – the value for the period was set to 0 and added to the semi data series. If it is 0, which is extremely unlikely, but whatever, it would also be 0. If it is less than 0, hoIver, which indicates underperformance, I would square the portfolio return, which already gives us the semi variance I need for our next step. From here, I can simply take the square root of the average of the ‘semi’ data series to get the daily downside risk and multiplying it by the square root of 252, which gives us the annual number. After that, I have all the numbers to calculate the Sortino ratio. • Information Ratio: The information ratio measures the portfolio returns compared to the returns of a benchmark index, i.e. S&P500, after adjusting for its additional risk. It only looks at the excess return of the portfolio over the benchmark and the volatility or risk associated with it. I already have all the inputs I need to calculate his ratio. Thus, I simply created a new dataframe with the portfolio returns of every period and the benchmark returns of every period. To find the excess return, i.e. the nominator, I simply subtracted the latter from the former and assigned it to a new variable, which I called ‘excess_return’. The nominator would be the average return of the portfolio minus the average return of the benchmark, and the denominator would be the standard deviation of the ‘excess_return’ series. Finally, I printed short sentences with the results for every conditioning variable just described as an output in the console.

Overview For this assignment you will be developing and implementing : An On-Demand shortest-hop Routing (ODR) protocol for networks of fixed but arbitrary and unknown connectivity, using PF_PACKET sockets. The implementation is based on (a simplified version of) the AODV algorithm. Time client and server applications that send requests and replies to each other across the network using ODR. An API you will implement using Unix domain datagram sockets enables applications to communicate with the ODR mechanism running locally at their nodes. I shall be discussing the assignment in class on Wednesday, October 29, and Monday, November 3. The following should prove useful reference material for the assignment : Sections 15.1, 15.2, 15.4 & 15.6, Chapter 15, on Unix domain datagram sockets. PF_PACKET(7) from the Linux manual pages. You might find these notes made by a past CSE 533 student useful. Also, the following link http://www.pdbuchan.com/rawsock/rawsock.html contains useful code samples that use PF_PACKET sockets (as well as other code samples that use raw IP sockets which you do not need for this assignment, though you will be using these types of sockets for Assignment 4). Charles E. Perkins & Elizabeth M. Royer. “Ad-hoc On-Demand Distance Vector Routing.” Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications, New Orleans, Louisiana, February 1999, pp. 90 - 100. The VMware environment minix.cs.stonybrook.edu is a Linux box running VMware. A cluster of ten Linux virtual machines, called vm1 through vm10, on which you can gain access as root and run your code have been created on minix. See VMware Environment Hosts for further details. VMware instructions takes you to a page that explains how to use the system. The ten virtual machines have been configured into a small virtual intranet of Ethernet LANs whose topology is (in principle) unknown to you. There is a course account cse533 on node minix, with home directory /users/cse533. In there, you will find a subdirectory Stevens/unpv13e , exactly as you are used to having on the cs system. You should develop your source code and makefiles for handing in accordingly. You will be handing in your source code on the minix node. Note that you do not need to link against the socket library (-lsocket) in Linux. The same is true for -lnsl and -lresolv. For example, take a look at how the LIBS variable is defined for Solaris, in /home/courses/cse533/Stevens/unpv13e_solaris2.10/Make.defines (on compserv1, say) : LIBS = ../libunp.a -lresolv -lsocket -lnsl -lpthread But if you take a look at Make.defines on minix (/users/cse533/Stevens/unpv13e/Make.defines) you will find only: LIBS = ../libunp.a -lpthread The nodes vm1 , . . . . . , vm10 are all multihomed : each has two (or more) interfaces. The interface ‘eth0 ’ should be completely ignored and is not to be used for this assignment (because it shows all ten nodes as if belonging to the same single Ethernet 192.168.1.0/24, rather than to an intranet composed of several Ethernets). Note that vm1 , . . . . . , vm10 are virtual machines, not real ones. One implication of this is that you will not be able to find out what their (virtual) IP addresses are by using nslookup and such. To find out these IP addresses, you need to look at the file /etc/hosts on minix. More to the point, invoking gethostbyname for a given vm will return to you only the (primary) IP address associated with the interface eth0 of that vm (which is the interface you will not be using). It will not return to you any other IP address for the node. Similarly, gethostbyaddr will return the vm node name only if you give it the (primary) IP address associated with the interface eth0 for the node. It will return nothing if you give it any other IP address for the node, even though the address is perfectly valid. Because of this, and because it will ease your task to be able to use gethostbyname and gethostbyaddr in a straightforward way, we shall adopt the (primary) IP addresses associated with interfaces eth0 as the ‘canonical’ IP addresses for the nodes (more on this below). Time client and server A time server runs on each of the ten vm machines. The client code should also be available on each vm so that it can be evoked at any of them. Normally, time clients/servers exchange request/reply messages using the TCP/UDP socket API that, effectively, enables them to receive service (indirectly, via the transport layer) from the local IP mechanism running at their nodes. You are to implement an API using Unix domain sockets to access the local ODR service directly (somewhat similar, in effect, to the way that raw sockets permit an application to access IP directly). Use Unix domain SOCK_DGRAM, rather than SOCK_STREAM, sockets (see Figures 15.5 & 15.6, pp. 418 - 419). API You need to implement a msg_send function that will be called by clients/servers to send requests/replies. The parameters of the function consist of : int giving the socket descriptor for write char* giving the ‘canonical’ IP address for the destination node, in presentation format int giving the destination ‘port’ number char* giving message to be sent int flag if set, force a route rediscovery to the destination node even if a non-‘stale’ route already exists (see below) msg_send will format these parameters into a single char sequence which is written to the Unix domain socket that a client/server process creates. The sequence will be read by the local ODR from a Unix domain socket that the ODR process creates for itself. Recall that the ‘canonical’ IP address for a vm node is the (primary) IP address associated with the eth0 interface for the node. It is what will be returned to you by a call to gethostbyname. Similarly, we need a msg_recv function which will do a (blocking) read on the application domain socket and return with : int giving socket descriptor for read char* giving message received char* giving ‘canonical’ IP address for the source node of message, in presentation format int* giving source ‘port’ number This information is written as a single char sequence by the ODR process to the domain socket that it creates for itself. It is read by msg_recv from the domain socket the client/server process creates, decomposed into the three components above, and returned to the caller of msg_recv. Also see the section below entitled ODR and the API. Client When a client is evoked at a node, it creates a domain datagram socket. The client should bind its socket to a ‘temporary’ (i.e., not ‘well-known’) sun_path name obtained from a call to tmpnam() (cf. line 10, Figure 15.6, p. 419) so that multiple clients may run at the same node. Note that tmpnam() is actually highly deprecated. You should use the mkstemp() function instead - look up the online man pages on minix (‘man mkstemp’) for details. As you run client code again and again during the development stage, the temporary files created by the calls to tmpnam / mkstemp start to proliferate since these files are not automatically removed when the client code terminates. You need to explicitly remove the file created by the client evocation by issuing a call to unlink() or to remove() in your client code just before the client code exits. See the online man pages on minix (‘man unlink’, ‘man remove’) for details. The client then enters an infinite loop repeating the steps below. The client prompts the user to choose one of vm1 , . . . . . , vm10 as a server node. Client msg_sends a 1 or 2 byte message to server and prints out on stdout the message client at node vm i1 sending request to server at vm i2 (In general, throughout this assignment, “trace” messages such as the one above should give the vm names and not IP addresses of the nodes.) Client then blocks in msg_recv awaiting response. This attempt to read from the domain socket should be backed up by a timeout in case no response ever comes. I leave it up to you whether you ‘wrap’ the call to msg_recv in a timeout, or you implement the timeout inside msg_recv itself. When the client receives a response it prints out on stdout the message client at node vm i1 : received from vm i2 <timestamp> If, on the other hand, the client times out, it should print out the message client at node vm i1 : timeout on response from vm i2 The client then retransmits the message out, setting the flag parameter in msg_send to force a route rediscovery, and prints out an appropriate message on stdout. This is done only once, when a timeout for a given message to the server occurs for the first time. Client repeats steps 1. - 3. Server The server creates a domain datagram socket. The server socket is assumed to have a (node-local) ‘well-known’ sun_path name which it binds to. This ‘well-known’ sun_path name is designated by a (network-wide) ‘well-known’ ‘port’ value. The time client uses this ‘port’ value to communicate with the server. The server enters an infinite sequence of calls to msg_recv followed by msg_send, awaiting client requests and responding to them. When it responds to a client request, it prints out on stdout the message server at node vm i1 responding to request from vm i2 ODR The ODR process runs on each of the ten vm machines. It is evoked with a single command line argument which gives a “staleness” time parameter, in seconds. It uses get_hw_addrs (available to you on minix in ~cse533/Asgn3_code) to obtain the index, and associated (unicast) IP and Ethernet addresses for each of the node’s interfaces, except for the eth0 and lo (loopback) interfaces, which should be ignored. In the subdirectory ~cse533/Asgn3_code (/users/cse533/Asgn3_code) on minix I am providing you with two functions, get_hw_addrs and prhwaddrs. These are analogous to the get_ifi_info_plus and prifinfo_plus of Assignment 2. Like get_ifi_info_plus, get_hw_addrs uses ioctl. get_hw_addrs gets the (primary) IP address, alias IP addresses (if any), HW address, and interface name and index value for each of the node's interfaces (including the loopback interface lo). prhwaddrs prints that information out. You should modify and use these functions as needed. Note that if an interface has no HW address associated with it (this is, typically, the case for the loopback interface lo for example), then ioctl returns get_hw_addrs a HW address which is the equivalent of 00:00:00:00:00:00 . get_hw_addrs stores this in the appropriate field of its data structures as it would with any HW address returned by ioctl, but when prhwaddrs comes across such an address, it prints a blank line instead of its usual ‘HWaddr = xx:xx:xx:xx:xx:xx’. The ODR process creates one or more PF_PACKET sockets. You will need to try out PF_PACKET sockets for yourselves and familiarize yourselves with how they behave. If, when you read from the socket and provide a sockaddr_ll structure, the kernel returns to you the index of the interface on which the incoming frame was received, then one socket will be enough. Otherwise, somewhat in the manner of Assignment 2, you shall have to create a PF_PACKET socket for every interface of interest (which are all the interfaces of the node, excluding interfaces lo and eth0 ), and bind a socket to each interface. Furthermore, if the kernel also returns to you the source Ethernet address of the frame in the sockaddr_ll structure, then you can make do with SOCK_DGRAM type PF_PACKET sockets; otherwise you shall have to use SOCK_RAW type sockets (although I would prefer you to use SOCK_RAW type sockets anyway, even if it turns out you can make do with SOCK_DGRAM type). The socket(s) should have a protocol value (no larger than 0xffff so that it fits in two bytes; this value is given as a network-byte-order parameter in the call(s) to function socket) that identifies your ODR protocol. The <linux/if_ether.h> include file (i.e., the file /usr/include/linux/if_ether.h) contains protocol values defined for the standard protocols typically found on an Ethernet LAN, as well as other values such as ETH_P_ALL. You should set protocol to a value of your choice which is not a <linux/if_ether.h> value, but which is, hopefully, unique to yourself. Remember that you will all be running your code using the same root account on the vm1 , . . . . . , vm10 nodes. So if two of you happen to choose the same protocol value and happen to be running on the same vm node at the same time, your applications will receive each other’s frames. For that reason, try to choose a protocol value for the socket(s) that is likely to be unique to yourself (something based on your Stony Brook student ID number, for example). This value effectively becomes the protocol value for your implementation of ODR, as opposed to some other cse 533 student's implementation. Because your value of protocol is to be carried in the frame type field of the Ethernet frame header, the value chosen should be not less than 1536 (0x600) so that it is not misinterpreted as the length of an Ethernet 802.3 frame. Note from the man pages for packet(7) that frames are passed to and from the socket without any processing in the frame content by the device driver on the other side of the socket, except for calculating and tagging on the 4-byte CRC trailer for outgoing frames, and stripping that trailer before delivering incoming frames to the socket. Nevertheless, if you write a frame that is less than 60 bytes, the necessary padding is automatically added by the device driver so that the frame that is actually transmitted out is the minimum Ethernet size of 64 bytes. When reading from the socket, however, any such padding that was introduced into a short frame at the sending node to bring it up to the minimum frame size is not stripped off - it is included in what you receive from the socket (thus, the minimum number of bytes you receive should never be less than 60). Also, you will have to build the frame header for outgoing frames yourselves (assuming you use SOCK_RAW type sockets). Bear in mind that the field values in that header have to be in network order. The ODR process also creates a domain datagram socket for communication with application processes at the node, and binds the socket to a ‘well known’ sun_path name for the ODR service. Because it is dealing with fixed topologies, ODR is, by and large, considerably simpler than AODV. In particular, discovered routes are relatively stable and there is no need for all the paraphernalia that goes with the possibility of routes changing (such as maintenance of active nodes in the routing tables and timeout mechanisms; timeouts on reverse links; lifetime field in the RREP messages; etc.) Nor will we be implementing source_sequence_#s (in the RREQ messages), and dest_sequence_# (in RREQ and RREP messages). In reality, we should (though we will not, for the sake of simplicity, be doing so) implement some sort of sequence number mechanism, or some alternative mechanism such as split-horizon for example, if we are to avoid possible scenarios of routing loops in a “count to infinity” context (I shall explain this point in class). However, we want ODR to discover shortest-hop paths, and we want it to do so in a reasonably efficient manner. This necessitates having one or two aspects of its operations work in a different, possibly slightly more complicated, way than AODV does. ODR has several basic responsibilities : Build and maintain a routing table. For each destination in the table, the routing table structure should include, at a minimum, the next-hop node (in the form of the Ethernet address for that node) and outgoing interface index, the number of hops to the destination, and a timestamp of when the the routing table entry was made or last “reconfirmed” / updated. Note that a destination node in the table is to be identified only by its ‘canonical’ IP address, and not by any other IP addresses the node has. Generate a RREQ in response to a time client calling msg_send for a destination for which ODR has no route (or for which a route exists, but msg_send has the flag parameter set or the route has gone ‘stale’ – see below), and ‘flood’ the RREQ out on all the node’s interfaces (except for the interface it came in on and, of course, the interfaces eth0 and lo). Flooding is done using an Ethernet broadcast destination address (0xff:ff:ff:ff:ff:ff) in the outgoing frame header. Note that a copy of the broadcast packet is supposed to / might be looped back to the node that sends it (see p. 535 in the Stevens textbook). ODR will have to take care not to treat these copies as new incoming RREQs. Also note that ODR at the client node increments the broadcast_id every time it issues a new RREQ for any destination node. When a RREQ is received, ODR has to generate a RREP if it is at the destination node, or if it is at an intermediate node that happens to have a route (which is not ‘stale’ – see below) to the destination. Otherwise, it must propagate the RREQ by flooding it out on all the node’s interfaces (except the interface the RREQ arrived on). Note that as it processes received RREQs, ODR should enter the ‘reverse’ route back to the source node into its routing table, or update an existing entry back to the source node if the RREQ received shows a shorter-hop route, or a route with the same number of hops but going through a different neighbour. The timestamp associated with the table entry should be updated whenever an existing route is either “reconfirmed” or updated. Obviously, if the node is going to generate a RREP, updating an existing entry back to the source node with a more efficient route, or a same-hops route using a different neighbour, should be done before the RREP is generated. Unlike AODV, when an intermediate node receives a RREQ for which it generates a RREP, it should nevertheless continue to flood the RREQ it received if the RREQ pertains to a source node whose existence it has heretofore been unaware of, or the RREQ gives it a more efficient route than it knew of back to the source node (the reason for continuing to flood the RREQ is so that other nodes in the intranet also become aware of the existence of the source node or of the potentially more optimal reverse route to it, and update their tables accordingly). However, since an RREP for this RREQ is being sent by our node, we do not want other nodes who receive the RREQ propagated by our node, and who might be in a position to do so, to also send RREPs. So we need to introduce a field in the RREQ message, not present in the AODV specifications, which acts like a “RREP already sent” field. Our node sets this field before further propagating the RREQ and nodes receiving an RREQ with this field set do not send RREPs in response, even if they are in a position to do so. ODR may, of course, receive multiple, distinct instances of the same RREQ (the combination of source_addr and broadcast_id uniquely identifies the RREQ). Such RREQs should not be flooded out unless they have a lower hop count than instances of that RREQ that had previously been received. By the same token, if ODR is in a position to send out a RREP, and has already done so for this, now repeating, RREQ , it should not send out another RREP unless the RREQ shows a more efficient, previously unknown, reverse route back to the source node. In other words, ODR should not generate essentially duplicative RREPs, nor generate RREPs to instances of RREQs that reflect reverse routes to the source that are not more efficient than what we already have. Relay RREPs received back to the source node (this is done using the ‘reverse’ route entered into the routing table when the corresponding RREQ was processed). At the same time, a ‘forward’ path to the destination is entered into the routing table. ODR could receive multiple, distinct RREPs for the same RREQ. The ‘forward’ route entered in the routing table should be updated to reflect the shortest-hop route to the destination, and RREPs reflecting suboptimal routes should not be relayed back to the source. In general, maintaining a route and its associated timestamp in the table in response to RREPs received is done in the same manner described above for RREQs. Forward time client/server messages along the next hop. (The following is important – you will lose points if you do not implement it.) Note that such application payload messages (especially if they are the initial request from the client to the server, rather than the server response back to the client) can be like “free” RREPs, enabling nodes along the path from source (client) to destination (server) node to build a reverse path back to the client node whose existence they were heretofore unaware of (or, possibly, to update an existing route with a more optimal one). Before it forwards an application payload message along the next hop, ODR at an intermediate node (and also at the final destination node) should use the message to update its routing table in this way. Thus, calls to msg_send by time servers should never cause ODR at the server node to initiate RREQs, since the receipt of a time client request implies that a route back to the client node should now exist in the routing table. The only exception to this is if the server node has a staleness parameter of zero (see below). A routing table entry has associated with it a timestamp that gives the time the entry was made into the table. When a client at a node calls msg_send, and if an entry for the destination node already exists in the routing table, ODR first checks that the routing information is not ‘stale’. A stale routing table entry is one that is older than the value defined by the staleness parameter given as a command line argument to the ODR process when it is executed. ODR deletes stale entries (as well as non-stale entries when the flag parameter in msg_send is set) and initiates a route rediscovery by issuing a RREQ for the destination node. This will force periodic updating of the routing tables to take care of failed nodes along the current path, Ethernet addresses that might have changed, and so on. Similarly, as RREQs propagate through the intranet, existing stale table entries at intermediate nodes are deleted and new route discoveries propagated. As noted above when discussing the processing of RREQs and RREPs, the associated timestamp for an existing table entry is updated in response to having the route either “reconfirmed” or updated (this applies to both reverse routes, by virtue of RREQs received, and to forward routes, by virtue of RREPs). Finally, note that a staleness parameter of 0 essentially indicates that the discovered route will be used only once, when first discovered, and then discarded. Effectively, an ODR with staleness parameter 0 maintains no real routing table at all ; instead, it forces route discoveries at every step of its operation. As a practical matter, ODR should be run with staleness parameter values that are considerably larger than the longest RTT on the intranet, otherwise performance will degrade considerably (and collapse entirely as the parameter values approach 0). Nevertheless, for robustness, we need to implement a mechanism by which an intermediate node that receives a RREP or application payload message for forwarding and finds that its relevant routing table entry has since gone stale, can intiate a RREQ to rediscover the route it needs. RREQ, RREP, and time client/server request/response messages will all have to be carried as encapsulated ODR protocol messages that form the data payload of Ethernet frames. So we need to design the structure of ODR protocol messages. The format should contain a type field (0 for RREQ, 1 for RREP, 2 for application payload ). The remaining fields in an ODR message will depend on what type it is. The fields needed for (our simplified versions of AODV’s) RREQ and RREP should be fairly clear to you, but keep in mind that you need to introduce two extra fields: The “RREP already sent” bit or field in RREQ messages, as mentioned above. A “forced discovery” bit or field in both RREQ and RREP messages: When a client application forces route rediscovery, this bit should be set in the RREQ issued by the client node ODR. Intermediate nodes that are not the destination node but which do have a route to the destination node should not respond with RREPs to an RREQ which has the forced discovery field set. Instead, they should continue to flood the RREQ so that it eventually reaches the destination node which will then respond with an RREP. The intermediate nodes relaying such an RREQ must update their ‘reverse’ route back to the source node accordingly, even if the new route is less efficient (i.e., has more hops) than the one they currently have in their routing table. The destination node responds to the RREQ with an RREP in which this field is also set. Intermediate nodes that receive such a forced discovery RREP must update their ‘forward’ route to the destination node accordingly, even if the new route is less efficient (i.e., has more hops) than the one they currently have in their routing table. This behaviour will cause a forced discovery RREQ to be responded to only by the destination node itself and not any other node, and will cause intermediate nodes to update their routing tables to both source and destination nodes in accordance with the latest routing information received, to cover the possibility that older routes are no longer valid because nodes and/or links along their paths have gone down. A type 2, application payload, message needs to contain the following type of information : type = 2 ‘canonical’ IP address of source node ‘port’ number of source application process (This, of course, is not a real port number in the TCP/UDP sense, but simply a value that ODR at the source node uses to designate the sun_path name for the source application’s domain socket.) ‘canonical’ IP address of destination node ‘port’ number of destination application process (This is passed to ODR by the application process at the source node when it calls msg_send. Its designates the sun_path name for an application’s domain socket at the destination node.) hop count (This starts at 0 and is incremented by 1 at each hop so that ODR can make use of the message to update its routing table, as discussed above.) number of bytes in application message The fields above essentially constitute a ‘header’ for the ODR message. Note that fields which you choose to have carry numeric values (rather than ascii characters, for example) must be in network byte order. ODR-defined numeric-valued fields in type 0, RREQ, and type 1, RREP, messages must, of course, also be in network byte order. Also note that only the ‘canonical’ IP addresses are used for the source and destination nodes in the ODR header. The same has to be true in the headers for type 0, RREQ, and type 1, RREP, messages. The general rule is that ODR messages only carry ‘canonical’ IP node addresses. The last field in the type 2 ODR message is essentially the data payload of the message. application message given in the call to msg_send An ODR protocol message is encapsulated as the data payload of an Ethernet frame whose header it fills in as follows : source address = Ethernet address of outgoing interface of the current node where ODR is processing the message. destination address = Ethernet broadcast address for type 0 messages; Ethernet address of next hop node for type 1 & 2 messages. protocol field = protocol value for the ODR PF_PACKET socket(s). Last but not least, whenever ODR writes an Ethernet frame out through its socket, it prints out on stdout the message ODR at node vm i1 : sending frame hdr src vm i1 dest addr ODR msg type n src vm i2 dest vm i3 where addr is in presentation format (i.e., hexadecimal xx:xx:xx:xx:xx:xx) and gives the destination Ethernet address in the outgoing frame header. Other nodes in the message should be identified by their vm name. A message should be printed out for each packet sent out on a distinct interface. ODR and the API When the ODR process first starts, it must construct a table in which it enters all well-known ‘port’ numbers and their corresponding sun_path names. These will constitute permanent entries in the table. Thereafter, whenever it reads a message off its domain socket, it must obtain the sun_path name for the peer process socket and check whether that name is entered in the table. If not, it must select an ‘ephemeral’ ‘port’ value by which to designate the peer sun_path name and enter the pair < port value , sun_path name > into the table. Such entries cannot be permanent otherwise the table will grow unboundedly in time, with entries surviving for ever, beyond the peer processes’ demise. We must associate a time_to_live field with a non-permanent table entry, and purge the entry if nothing is heard from the peer for that amount of time. Every time a peer process for which a non-permanent table entry exists communicates with ODR, its time_to_live value should be reinitialized. Note that when ODR writes to a peer, it is possible for the write to fail because the peer does not exist : it could be a ‘well-known’ service that is not running, or we could be in the interval between a process with a non-permanent table entry terminating and the expiration of its time_to_live value. Notes A proper implementation of ODR would probably require that RREQ and RREP messages be backed up by some kind of timeout and retransmission mechanism since the network transmission environment is not reliable. This would considerably complicate the implementation (because at any given moment, a node could have multiple RREQs that it has flooded out, but for which it has still not received RREPs; the situation is further complicated by the fact that not all intermediate nodes receiving and relaying RREQs necessarily lie on a path to the destination, and therefore should expect to receive RREPs), and, learning-wise, would not add much to the experience you should have gained from Assignment 2.

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This XML file does not appear to have any style information associated with it. The document tree is shown below. <xsd:schema xmlns="http://www.springframework.org/schema/mvc" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:tool="http://www.springframework.org/schema/tool" targetNamespace="http://www.springframework.org/schema/mvc" elementFormDefault="qualified" attributeFormDefault="unqualified"> <xsd:import namespace="http://www.springframework.org/schema/beans" schemaLocation="https://www.springframework.org/schema/beans/spring-beans-4.3.xsd"/> <xsd:import namespace="http://www.springframework.org/schema/tool" schemaLocation="https://www.springframework.org/schema/tool/spring-tool-4.3.xsd"/> <xsd:element name="annotation-driven"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"> <![CDATA[ Configures the annotation-driven Spring MVC Controller programming model. Note that this tag works in Web MVC only, not in Portlet MVC! See org.springframework.web.servlet.config.annotation.EnableWebMvc javadoc for details on code-based alternatives to enabling annotation-driven Spring MVC support. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:all minOccurs="0"> <xsd:element name="path-matching" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configures the path matching part of the Spring MVC Controller programming model. Like annotation-driven, code-based alternatives are also documented in EnableWebMvc javadoc. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="suffix-pattern" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to use suffix pattern match (".*") when matching patterns to requests. If enabled a method mapped to "/users" also matches to "/users.*". The default value is true. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="trailing-slash" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to match to URLs irrespective of the presence of a trailing slash. If enabled a method mapped to "/users" also matches to "/users/". The default value is true. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="registered-suffixes-only" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether suffix pattern matching should work only against path extensions explicitly registered when you configure content negotiation. This is generally recommended to reduce ambiguity and to avoid issues such as when a "." appears in the path for other reasons. The default value is false. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="path-helper" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The bean name of the UrlPathHelper to use for resolution of lookup paths. Use this to override the default UrlPathHelper with a custom subclass, or to share common UrlPathHelper settings across multiple HandlerMappings and MethodNameResolvers. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="path-matcher" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The bean name of the PathMatcher implementation to use for matching URL paths against registered URL patterns. Default is AntPathMatcher. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="message-converters" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configures one or more HttpMessageConverter types to use for converting @RequestBody method parameters and @ResponseBody method return values. Using this configuration element is optional. HttpMessageConverter registrations provided here will take precedence over HttpMessageConverter types registered by default. Also see the register-defaults attribute if you want to turn off default registrations entirely. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:choice maxOccurs="unbounded"> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation> <![CDATA[ An HttpMessageConverter bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation> <![CDATA[ A reference to an HttpMessageConverter bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:sequence> <xsd:attribute name="register-defaults" type="xsd:boolean" default="true"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether or not default HttpMessageConverter registrations should be added in addition to the ones provided within this element. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="argument-resolvers" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configures HandlerMethodArgumentResolver types to support custom controller method argument types. Using this option does not override the built-in support for resolving handler method arguments. To customize the built-in support for argument resolution configure RequestMappingHandlerAdapter directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:choice minOccurs="1" maxOccurs="unbounded"> <xsd:element ref="beans:bean" minOccurs="0" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ The HandlerMethodArgumentResolver (or WebArgumentResolver for backwards compatibility) bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref" minOccurs="0" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ A reference to a HandlerMethodArgumentResolver bean definition. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.web.method.support.HandlerMethodArgumentResolver"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:complexType> </xsd:element> <xsd:element name="return-value-handlers" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configures HandlerMethodReturnValueHandler types to support custom controller method return value handling. Using this option does not override the built-in support for handling return values. To customize the built-in support for handling return values configure RequestMappingHandlerAdapter directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:choice minOccurs="1" maxOccurs="unbounded"> <xsd:element ref="beans:bean" minOccurs="0" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ The HandlerMethodReturnValueHandler bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref" minOccurs="0" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ A reference to a HandlerMethodReturnValueHandler bean definition. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.web.method.support.HandlerMethodReturnValueHandler"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:complexType> </xsd:element> <xsd:element name="async-support" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure options for asynchronous request processing. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:all minOccurs="0"> <xsd:element name="callable-interceptors" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ The ordered set of interceptors that intercept the lifecycle of concurrently executed requests, which start after a controller returns a java.util.concurrent.Callable. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element ref="beans:bean" minOccurs="1" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ Registers a CallableProcessingInterceptor. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="deferred-result-interceptors" minOccurs="0"> <xsd:annotation> <xsd:documentation> <![CDATA[ The ordered set of interceptors that intercept the lifecycle of concurrently executed requests, which start after a controller returns a DeferredResult. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element ref="beans:bean" minOccurs="1" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ Registers a DeferredResultProcessingInterceptor. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:all> <xsd:attribute name="task-executor" type="xsd:string"> <xsd:annotation> <xsd:documentation source="java:org.springframework.core.task.AsyncTaskExecutor"> <![CDATA[ The bean name of a default AsyncTaskExecutor to use when a controller method returns a {@link Callable}. Controller methods can override this default on a per-request basis by returning an AsyncTask. By default, a SimpleAsyncTaskExecutor is used which does not re-use threads and is not recommended for production. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.core.task.AsyncTaskExecutor"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="default-timeout" type="xsd:long"> <xsd:annotation> <xsd:documentation> <![CDATA[ Specify the amount of time, in milliseconds, before asynchronous request handling times out. In Servlet 3, the timeout begins after the main request processing thread has exited and ends when the request is dispatched again for further processing of the concurrently produced result. If this value is not set, the default timeout of the underlying implementation is used, e.g. 10 seconds on Tomcat with Servlet 3. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> </xsd:all> <xsd:attribute name="conversion-service" type="xsd:string"> <xsd:annotation> <xsd:documentation source="java:org.springframework.core.convert.ConversionService"> <![CDATA[ The bean name of the ConversionService that is to be used for type conversion during field binding. This attribute is not required, and only needs to be specified if custom converters need to be configured. If not specified, a default FormattingConversionService is registered with converters to/from common value types. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.core.convert.ConversionService"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="validator" type="xsd:string"> <xsd:annotation> <xsd:documentation source="java:org.springframework.validation.Validator"> <![CDATA[ The bean name of the Validator that is to be used to validate Controller model objects. This attribute is not required, and only needs to be specified if a custom Validator needs to be configured. If not specified, JSR-303 validation will be installed if a JSR-303 provider is present on the classpath. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.validation.Validator"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="content-negotiation-manager" type="xsd:string"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.accept.ContentNegotiationManager"> <![CDATA[ The bean name of a ContentNegotiationManager that is to be used to determine requested media types. If not specified, a default ContentNegotiationManager is configured that checks the request path extension first and the "Accept" header second where path extensions such as ".json", ".xml", ".atom", and ".rss" are recognized if Jackson, JAXB2, or the Rome libraries are available. As a fallback option, the path extension is also used to perform a lookup through the ServletContext and the Java Activation Framework (if available). ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.web.accept.ContentNegotiationManager"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="message-codes-resolver" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The bean name of a MessageCodesResolver to use to build message codes from data binding and validation error codes. This attribute is not required. If not specified the DefaultMessageCodesResolver is used. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.validation.MessageCodesResolver"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="enable-matrix-variables" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Matrix variables can appear in any path segment, each matrix variable separated with a ";" (semicolon). For example "/cars;color=red;year=2012". By default, they're removed from the URL. If this property is set to true, matrix variables are not removed from the URL, and the request mapping pattern must use URI variable in path segments where matrix variables are expected. For example "/{cars}". Matrix variables can then be injected into a controller method with @MatrixVariable. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="ignore-default-model-on-redirect" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ By default, the content of the "default" model is used both during rendering and redirect scenarios. Alternatively a controller method can declare a RedirectAttributes argument and use it to provide attributes for a redirect. Setting this flag to true ensures the "default" model is never used in a redirect scenario even if a RedirectAttributes argument is not declared. Setting it to false means the "default" model may be used in a redirect if the controller method doesn't declare a RedirectAttributes argument. The default setting is false but new applications should consider setting it to true. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:complexType name="content-version-strategy"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ContentVersionStrategy"> <![CDATA[ A VersionStrategy that calculates an Hex MD5 hashes from the content of the resource and appends it to the file name, e.g. "styles/main-e36d2e05253c6c7085a91522ce43a0b4.css". ]]> </xsd:documentation> </xsd:annotation> <xsd:attribute name="patterns" type="xsd:string" use="required"/> </xsd:complexType> <xsd:complexType name="fixed-version-strategy"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.FixedVersionStrategy"> <![CDATA[ A VersionStrategy that relies on a fixed version applied as a request path prefix, e.g. reduced SHA, version name, release date, etc. ]]> </xsd:documentation> </xsd:annotation> <xsd:attribute name="version" type="xsd:string" use="required"/> <xsd:attribute name="patterns" type="xsd:string" use="required"/> </xsd:complexType> <xsd:complexType name="resource-version-strategy"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.VersionStrategy"> <![CDATA[ A strategy for extracting and embedding a resource version in its URL path. ]]> </xsd:documentation> </xsd:annotation> <xsd:choice minOccurs="1" maxOccurs="1"> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.VersionStrategy"> <![CDATA[ A VersionStrategy bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.VersionStrategy"> <![CDATA[ A reference to a VersionStrategy bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> <xsd:attribute name="patterns" type="xsd:string" use="required"/> </xsd:complexType> <xsd:complexType name="version-resolver"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.VersionResourceResolver"> <![CDATA[ Resolves request paths containing a version string that can be used as part of an HTTP caching strategy in which a resource is cached with a far future date (e.g. 1 year) and cached until the version, and therefore the URL, is changed. ]]> </xsd:documentation> </xsd:annotation> <xsd:choice maxOccurs="unbounded"> <xsd:element type="content-version-strategy" name="content-version-strategy"/> <xsd:element type="fixed-version-strategy" name="fixed-version-strategy"/> <xsd:element type="resource-version-strategy" name="version-strategy"/> </xsd:choice> </xsd:complexType> <xsd:complexType name="resource-resolvers"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceResolver"> <![CDATA[ A list of ResourceResolver beans definition and references. A ResourceResolver provides mechanisms for resolving an incoming request to an actual Resource and for obtaining the public URL path that clients should use when requesting the resource. ]]> </xsd:documentation> </xsd:annotation> <xsd:sequence> <xsd:choice maxOccurs="unbounded"> <xsd:element type="version-resolver" name="version-resolver"/> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceResolver"> <![CDATA[ A ResourceResolver bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceResolver"> <![CDATA[ A reference to a ResourceResolver bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:sequence> </xsd:complexType> <xsd:complexType name="resource-transformers"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceTransformer"> <![CDATA[ A list of ResourceTransformer beans definition and references. A ResourceTransformer provides mechanisms for transforming the content of a resource. ]]> </xsd:documentation> </xsd:annotation> <xsd:sequence> <xsd:choice maxOccurs="unbounded"> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceTransformer"> <![CDATA[ A ResourceTransformer bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.resource.ResourceTransformer"> <![CDATA[ A reference to a ResourceTransformer bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:sequence> </xsd:complexType> <xsd:complexType name="resource-chain"> <xsd:annotation> <xsd:documentation source="org.springframework.web.servlet.config.annotation.ResourceChainRegistration"> <![CDATA[ Assists with the registration of resource resolvers and transformers. Unless set to "false", the auto-registration adds default Resolvers (a PathResourceResolver) and Transformers (CssLinkResourceTransformer, if a VersionResourceResolver has been manually registered). The resource-cache attribute sets whether to cache the result of resource resolution/transformation; setting this to "true" is recommended for production (and "false" for development). A custom Cache can be configured if a CacheManager is provided as a bean reference in the "cache-manager" attribute, and the cache name provided in the "cache-name" attribute. ]]> </xsd:documentation> </xsd:annotation> <xsd:sequence> <xsd:element name="resolvers" type="resource-resolvers" minOccurs="0" maxOccurs="1"/> <xsd:element name="transformers" type="resource-transformers" minOccurs="0" maxOccurs="1"/> </xsd:sequence> <xsd:attribute name="resource-cache" type="xsd:boolean" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether the resource chain should cache resource resolution. Note that the resource content itself won't be cached, but rather Resource instances. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="auto-registration" type="xsd:boolean" default="true" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to register automatically ResourceResolvers and ResourceTransformers. Setting this property to "false" means that it gives developers full control over the registration process. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-manager" type="xsd:string" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ The name of the Cache Manager to cache resource resolution. By default, a ConcurrentCacheMap will be used. Since Resources aren't serializable and can be dependent on the application host, one should not use a distributed cache but rather an in-memory cache. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-name" type="xsd:string" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ The cache name to use in the configured cache manager. Will use "spring-resource-chain-cache" by default. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> <xsd:complexType name="cache-control"> <xsd:annotation> <xsd:documentation source="org.springframework.web.cache.CacheControl"> <![CDATA[ Generates "Cache-Control" HTTP response headers. ]]> </xsd:documentation> </xsd:annotation> <xsd:attribute name="must-revalidate" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "must-revalidate" directive in the Cache-Control header. This indicates that caches should revalidate the cached response when it's become stale. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="no-cache" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "no-cache" directive in the Cache-Control header. This indicates that caches should always revalidate cached response with the server. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="no-store" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "no-store" directive in the Cache-Control header. This indicates that caches should never cache the response. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="no-transform" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "no-transform" directive in the Cache-Control header. This indicates that caches should never transform (i.e. compress, optimize) the response content. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-public" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "public" directive in the Cache-Control header. This indicates that any cache MAY store the response. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-private" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "private" directive in the Cache-Control header. This indicates that the response is intended for a single user and may not be stored by shared caches. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="proxy-revalidate" type="xsd:boolean" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "proxy-revalidate" directive in the Cache-Control header. This directive has the same meaning as the "must-revalidate" directive, except it only applies to shared caches. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="max-age" type="xsd:int" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "max-age" directive in the Cache-Control header. This indicates that the response should be cached for the given number of seconds. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="s-maxage" type="xsd:int" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "s-maxage" directive in the Cache-Control header. This directive has the same meaning as the "max-age" directive, except it only applies to shared caches. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="stale-while-revalidate" type="xsd:int" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "stale-while-revalidate" directive in the Cache-Control header. This indicates that caches may serve the response after it becomes stale up to the given number of seconds. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="stale-if-error" type="xsd:int" use="optional"> <xsd:annotation> <xsd:documentation> <![CDATA[ Adds a "stale-if-error" directive in the Cache-Control header. When an error is encountered, a cached stale response may be used for the given number of seconds. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> <xsd:element name="resources"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.resource.ResourceHttpRequestHandler"> <![CDATA[ Configures a handler for serving static resources such as images, js, and, css files with cache headers optimized for efficient loading in a web browser. Allows resources to be served out of any path that is reachable via Spring's Resource handling. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="cache-control" type="cache-control" minOccurs="0" maxOccurs="1"/> <xsd:element name="resource-chain" type="resource-chain" minOccurs="0" maxOccurs="1"/> </xsd:sequence> <xsd:attribute name="mapping" use="required" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The URL mapping pattern within the current Servlet context to use for serving resources from this handler, such as "/resources/**" ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="location" use="required" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The resource location from which to serve static content, specified at a Spring Resource pattern. Each location must point to a valid directory. Multiple locations may be specified as a comma-separated list, and the locations will be checked for a given resource in the order specified. For example, a value of "/, classpath:/META-INF/public-web-resources/" will allow resources to be served both from the web app root and from any JAR on the classpath that contains a /META-INF/public-web-resources/ directory, with resources in the web app root taking precedence. For URL-based resources (e.g. files, HTTP URLs, etc) this property supports a special prefix to indicate the charset associated with the URL so that relative paths appended to it can be encoded correctly, e.g. "[charset=Windows-31J]https://example.org/path". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-period" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Specifies the cache period for the resources served by this resource handler, in seconds. The default is to not send any cache headers but rather to rely on last-modified timestamps only. Set this to 0 in order to send cache headers that prevent caching, or to a positive number of seconds in order to send cache headers with the given max-age value. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="order" type="xsd:token"> <xsd:annotation> <xsd:documentation> <![CDATA[ Specifies the order of the HandlerMapping for the resource handler. The default order is Ordered.LOWEST_PRECEDENCE - 1. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="default-servlet-handler"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler"> <![CDATA[ Configures a handler for serving static resources by forwarding to the Servlet container's default Servlet. Use of this handler allows using a "/" mapping with the DispatcherServlet while still utilizing the Servlet container to serve static resources. This handler will forward all requests to the default Servlet. Therefore it is important that it remains last in the order of all other URL HandlerMappings. That will be the case if you use the "annotation-driven" element or alternatively if you are setting up your customized HandlerMapping instance be sure to set its "order" property to a value lower than that of the DefaultServletHttpRequestHandler, which is Integer.MAX_VALUE. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="default-servlet-name" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The name of the default Servlet to forward to for static resource requests. The handler will try to autodetect the container's default Servlet at startup time using a list of known names. If the default Servlet cannot be detected because of using an unknown container or because it has been manually configured, the servlet name must be set explicitly. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="interceptors"> <xsd:annotation> <xsd:documentation> <![CDATA[ The ordered set of interceptors that intercept HTTP Servlet Requests handled by Controllers. Interceptors allow requests to be pre/post processed before/after handling. Each interceptor must implement the org.springframework.web.servlet.HandlerInterceptor or org.springframework.web.context.request.WebRequestInterceptor interface. The interceptors in this set are automatically detected by every registered HandlerMapping. The URI paths each interceptor applies to are configurable. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:choice maxOccurs="unbounded"> <xsd:choice> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Registers an interceptor that intercepts every request regardless of its URI path.. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation> <![CDATA[ Registers an interceptor that intercepts every request regardless of its URI path.. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> <xsd:element name="interceptor"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.handler.MappedInterceptor"> <![CDATA[ Registers an interceptor that interceptors requests sent to one or more URI paths. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="mapping" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ A path into the application intercepted by this interceptor. Exact path mapping URIs (such as "/myPath") are supported as well as Ant-stype path patterns (such as /myPath/**). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="exclude-mapping" minOccurs="0" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ A path into the application that should not be intercepted by this interceptor. Exact path mapping URIs (such as "/admin") are supported as well as Ant-stype path patterns (such as /admin/**). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:choice> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation> <![CDATA[ The interceptor's bean definition. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation> <![CDATA[ A reference to an interceptor bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:choice> <xsd:attribute name="path-matcher" type="xsd:string"> <xsd:annotation> <xsd:documentation source="java:org.springframework.util.PathMatcher"> <![CDATA[ The bean name of a PathMatcher implementation to use with nested interceptors. This is an optional, advanced property required only if using custom PathMatcher implementations that support mapping metadata other than the Ant path patterns supported by default. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:org.springframework.util.PathMatcher"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="view-controller"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.mvc.ParameterizableViewController"> <![CDATA[ Map a simple (logic-less) view controller to a specific URL path (or pattern) in order to render a response with a pre-configured status code and view. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The URL path (or pattern) the controller is mapped to. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="view-name" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the view name to return. Optional. If not specified, the view controller will return null as the view name in which case the configured RequestToViewNameTranslator will select the view name. The DefaultRequestToViewNameTranslator for example translates "/foo/bar" to "foo/bar". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="status-code" type="xsd:int"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the status code to set on the response. Optional. If not set the response status will be 200 (OK). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="redirect-view-controller"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.mvc.ParameterizableViewController"> <![CDATA[ Map a simple (logic-less) view controller to the given URL path (or pattern) in order to redirect to another URL. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The URL path (or pattern) the controller is mapped to. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="redirect-url" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ By default, the redirect URL is expected to be relative to the current ServletContext, i.e. as relative to the web application root. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="status-code" type="xsd:int"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the specific redirect 3xx status code to use. If not set, org.springframework.web.servlet.view.RedirectView will select MOVED_TEMPORARILY (302) by default. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="context-relative" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to interpret a given redirect URL that starts with a slash ("/") as relative to the current ServletContext, i.e. as relative to the web application root. The default is "true". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="keep-query-params" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to propagate the query parameters of the current request through to the target redirect URL. The default is "false". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="status-controller"> <xsd:annotation> <xsd:documentation source="java:org.springframework.web.servlet.mvc.ParameterizableViewController"> <![CDATA[ Map a simple (logic-less) controller to the given URL path (or pattern) in order to sets the response status to the given code without rendering a body. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The URL path (or pattern) the controller is mapped to. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="status-code" type="xsd:int" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The status code to set on the response. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:complexType name="contentNegotiationType"> <xsd:all> <xsd:element name="default-views" minOccurs="0"> <xsd:complexType> <xsd:sequence> <xsd:choice maxOccurs="unbounded"> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation> <![CDATA[ A bean definition for an org.springframework.web.servlet.View class. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation> <![CDATA[ A reference to a bean for an org.springframework.web.servlet.View class. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:all> <xsd:attribute name="use-not-acceptable" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Indicate whether a 406 Not Acceptable status code should be returned if no suitable view can be found. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> <xsd:complexType name="urlViewResolverType"> <xsd:attribute name="prefix" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The prefix that gets prepended to view names when building a URL. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="suffix" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The suffix that gets appended to view names when building a URL. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-views" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Enable or disable thew caching of resolved views. Default is "true": caching is enabled. Disable this only for debugging and development. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="view-class" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The view class that should be used to create views. Configure this if you want to provide a custom View implementation, typically a ub-class of the expected View type. ]]> </xsd:documentation> <xsd:appinfo> <tool:annotation kind="ref"> <tool:expected-type type="java:java.lang.Class"/> </tool:annotation> </xsd:appinfo> </xsd:annotation> </xsd:attribute> <xsd:attribute name="view-names" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the view names (or name patterns) that can be handled by this view resolver. View names can contain simple wildcards such that 'my*', '*Report' and '*Repo*' will all match the view name 'myReport'. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> <xsd:element name="view-resolvers"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure a chain of ViewResolver instances to resolve view names returned from controllers into actual view instances to use for rendering. All registered resolvers are wrapped in a single (composite) ViewResolver with its order property set to 0 so that other external resolvers may be ordere ]]> <![CDATA[ d before or after it. When content negotiation is enabled the order property is set to highest priority instead with the ContentNegotiatingViewResolver encapsulating all other registered view resolver instances. That way the resolvers registered through the MVC namespace form self-encapsulated resolver chain. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:choice minOccurs="1" maxOccurs="unbounded"> <xsd:element name="content-negotiation" type="contentNegotiationType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Registers a ContentNegotiatingViewResolver with the list of all other registered ViewResolver instances used to set its "viewResolvers" property. See the javadoc of ContentNegotiatingViewResolver for more details. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="jsp" type="urlViewResolverType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register an InternalResourceViewResolver bean for JSP rendering. By default, "/WEB-INF/" is registered as a view name prefix and ".jsp" as a suffix. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="tiles" type="urlViewResolverType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a TilesViewResolver based on Tiles 3.x. To configure Tiles you must also add a top-level <mvc:tiles-configurer> element or declare a TilesConfigurer bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="freemarker" type="urlViewResolverType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a FreeMarkerViewResolver. By default, ".ftl" is configured as a view name suffix. To configure FreeMarker you must also add a top-level <mvc:freemarker-configurer> element or declare a FreeMarkerConfigurer bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="groovy" type="urlViewResolverType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a GroovyMarkupViewResolver. By default, ".tpl" is configured as a view name suffix. To configure the Groovy markup template engine you must also add a top-level <mvc:groovy-configurer> element or declare a GroovyMarkupConfigurer bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="script-template" type="urlViewResolverType"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a ScriptTemplateViewResolver. To configure the Script engine you must also add a top-level <mvc:script-template-configurer> element or declare a ScriptTemplateConfigurer bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element name="bean-name" maxOccurs="1"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a BeanNameViewResolver bean. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:bean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a ViewResolver as a direct bean declaration. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> <xsd:element ref="beans:ref"> <xsd:annotation> <xsd:documentation> <![CDATA[ Register a ViewResolver through references to an existing bean declaration. ]]> </xsd:documentation> </xsd:annotation> </xsd:element> </xsd:choice> <xsd:attribute name="order" type="xsd:int"> <xsd:annotation> <xsd:documentation> <![CDATA[ ViewResolver's registered through this element are encapsulated in an instance of org.springframework.web.servlet.view.ViewResolverComposite and follow the order of registration. This attribute determines the order of the ViewResolverComposite itself relative to any additional ViewResolver's (not registered through this element) present in the Spring configuration By default this property is not set, which means the resolver is ordered at Ordered.LOWEST_PRECEDENCE unless content negotiation is enabled in which case the order (if not set explicitly) is changed to Ordered.HIGHEST_PRECEDENCE. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="tiles-configurer"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure Tiles 3.x by registering a TilesConfigurer bean. This is a shortcut alternative to declaring a TilesConfigurer bean directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="definitions" minOccurs="0" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="location" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The location of a file containing Tiles definitions (or a Spring resource pattern). If no Tiles definitions are registerd, then "/WEB-INF/tiles.xml" is expected to exists. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> </xsd:sequence> <xsd:attribute name="check-refresh" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to check Tiles definition files for a refresh at runtime. Default is "false". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="validate-definitions" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether to validate the Tiles XML definitions. Default is "true". ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="definitions-factory" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The Tiles DefinitionsFactory class to use. Default is Tiles' default. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="preparer-factory" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The Tiles PreparerFactory class to use. Default is Tiles' default. Consider "org.springframework.web.servlet.view.tiles3.SimpleSpringPreparerFactory" or "org.springframework.web.servlet.view.tiles3.SpringBeanPreparerFactory" (see javadoc). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="freemarker-configurer"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure FreeMarker for view resolution by registering a FreeMarkerConfigurer bean. This is a shortcut alternative to declaring a FreeMarkerConfigurer bean directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="template-loader-path" minOccurs="0" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="location" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The location of a FreeMarker template loader path (or a Spring resource pattern). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="groovy-configurer"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure the Groovy markup template engine for view resolution by registering a GroovyMarkupConfigurer bean. This is a shortcut alternative to declaring a GroovyMarkupConfigurer bean directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="auto-indent" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether you want the template engine to render indents automatically. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="cache-templates" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ If enabled templates are compiled once for each source (URL or File). It is recommended to keep this flag to true unless you are in development mode and want automatic reloading of templates. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="resource-loader-path" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The Groovy markup template engine resource loader path via a Spring resource location. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="script-template-configurer"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure the script engine for view resolution by registering a ScriptTemplateConfigurer bean. This is a shortcut alternative to declaring a ScriptTemplateConfigurer bean directly. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="script" minOccurs="0" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="location" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The location of the script to be loaded by the script engine (library or user provided). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> </xsd:sequence> <xsd:attribute name="engine-name" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ The script engine name to use by the view. The script engine must implement Invocable. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="render-object" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The object where belong the render function. For example, in order to call Mustache.render(), renderObject should be set to Mustache and renderFunction to render. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="render-function" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the render function name. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="content-type" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the content type to use for the response (text/html by default). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="charset" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Set the charset used to read script and template files (UTF-8 by default). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="resource-loader-path" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ The script engine resource loader path via a Spring resource location. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="shared-engine" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ When set to false, use thread-local ScriptEngine instances instead of one single shared instance. This flag should be set to false for those using non thread-safe script engines with templating libraries not designed for concurrency, like Handlebars or React running on Nashorn for example. In this case, Java 8u60 or greater is required due to this bug: https://bugs.openjdk.java.net/browse/JDK-8076099. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> <xsd:element name="cors"> <xsd:annotation> <xsd:documentation> <![CDATA[ Configure cross origin requests processing. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="mapping" minOccurs="1" maxOccurs="unbounded"> <xsd:annotation> <xsd:documentation> <![CDATA[ Enable cross origin requests processing on the specified path pattern. By default, all origins, GET HEAD POST methods, all headers and credentials are allowed and max age is set to 30 minutes. ]]> </xsd:documentation> </xsd:annotation> <xsd:complexType> <xsd:attribute name="path" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation> <![CDATA[ A path into the application that should handle CORS requests. Exact path mapping URIs (such as "/admin") are supported as well as Ant-stype path patterns (such as /admin/**). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="allowed-origins" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Comma-separated list of origins to allow, e.g. "https://domain1.com, https://domain2.com". The special value "*" allows all domains (default). Note that CORS checks use values from "Forwarded" (RFC 7239), "X-Forwarded-Host", "X-Forwarded-Port", and "X-Forwarded-Proto" headers, if present, in order to reflect the client-originated address. Consider using the ForwardedHeaderFilter in order to choose from a central place whether to extract and use such headers, or whether to discard them. See the Spring Framework reference for more on this filter. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="allowed-methods" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Comma-separated list of HTTP methods to allow, e.g. "GET, POST". The special value "*" allows all method. By default GET, HEAD and POST methods are allowed. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="allowed-headers" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Comma-separated list of headers that a pre-flight request can list as allowed for use during an actual request. The special value of "*" allows actual requests to send any header (default). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="exposed-headers" type="xsd:string"> <xsd:annotation> <xsd:documentation> <![CDATA[ Comma-separated list of response headers other than simple headers (i.e. Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma) that an actual response might have and can be exposed. Empty by default. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="allow-credentials" type="xsd:boolean"> <xsd:annotation> <xsd:documentation> <![CDATA[ Whether user credentials are supported (true by default). ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="max-age" type="xsd:long"> <xsd:annotation> <xsd:documentation> <![CDATA[ How long, in seconds, the response from a pre-flight request can be cached by clients. 1800 seconds (30 minutes) by default. ]]> </xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:schema>

become root by being on the docker group

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Become a root on host using docker

Become your own root CA to issue certificates

🔐 Become a root user and take advantage over the given system

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Toy design for cognitive & language skills of children with Downs Syndrome Abstract: The main objective has been to identify the root problem faced by the children who suffer from Down Syndrome. After intense research, a major problem identified which hasn’t had a lot of intervention done is that of cognitive & language skills development. In the market, most toys help the children with motor skill development and the ones for cognitive & language skills are either very poorly designed or are extremely expensive & not adapted to the Indian scenario. There is a huge gap in this sector in terms of toys to aid language and cognitive skills, hence the problem statement that is going to be tackled as a part of this project is to design a toy to aid cognitive & language skills of children affected by Down Syndrome, as well as to be inclusive enough to be used by able children. Through this statement, we are restricting ourselves to target a very specific problem & make life easier for the children as well as the teachers and the parents associated with them. Summary: The name of this toy is Octobud. It consists of a toy linked with an app on the phone of the parents of the children with Down Syndrome. It is a balance between a cuddly companion for the child and teacher. Its relevance is as follows - Targets the issue of lack of cognitive & language development that exists with the children suffering from Down Syndrome. Children with Down syndrome love having companions & get very attached to toys that give feedback and develop constantly. This toy has a place for a temporary screen (i.e. a phone screen) and is linked with an app that can be downloaded by the parents. This app is linked with the tentacles of the Octopus. Each tentacle is linked to one skill. Pressing the respective tentacle will trigger that skill when the phone is placed inside the phone holder of the toy. The app teaches the child the specific skill as per different levels of difficulty based on the ability of the child. The skill is taught through audio visuals. To prevent phone addiction & eye damage, once the skill to be taught is selected, the phone screen becomes unresponsive to touch & the app automatically shuts off after use for 20 minutes. It cannot be reused unless there’s a gap of at least 3 hours. The toy has been ergonomically designed and the tentacles thickness has been formulated as per anthropometric dimensions measured of the children so that it is easy for them to press the toy. The phone holder is attached to a box placed inside the toy which can be accessed by removing the strips below the toy. This box contains all of the engineering components of the toy. The box can be removed & charged by the parents by removing the strip below the octopus. The form of an octopus has been selected since it’s 8 tentacles align well with the 8 skills being taught. Also, its a cute creature relevant to toys. These skills are related to language development. The skills being taught through this toy are as follows - Alphabets, words, sentences, poems, colours, manners, numbers and a specific special edition pack that gets updated with the app. The toy records the voice of the child repeating after what is being said in the app and if the child says something correctly, feedback of clapping & colourful lights is given. The toy also comes with an attachment of starfish that light up on applying pressure. These can be given to the kids by the parents if the kids do a good job in learning and repeating correctly. This feedback will ensure that the kid enjoys the toy & learns well. The idea of using the phone for a screen was to reduce the cost a bit & to look at the phone not as an interactive interface for the child but as a temporary screen that can be removed from the phone to prevent any kind of addictions. Children who have Down syndrome are very calm and do not throw toys around. However, in an extreme case, if a child does end up throwing the Octobud, the toy has enough protection & the phone is placed very inside hence there will be no issue related to damage of parts.

Require the following tasks can become as root user.

How to become a root CA

Exploit an ISO and become root

Try this script and become a root !!

Information security challenge, taking advantage of a vulnerable ISO and its systems to become root.

opens a text editor, but first asks to become root if you don't have permission

Root repo for the course vteam at BTH. Contains submodules and becomes a full system for renting bikes.

This project is to boost a root code so it's becomes a root code that you can flash to [any] version of open source Android is/ operating system

In the following Jupyer notebook, we become more familiar with (py)ROOT by obtaining the di-Photon invariant mass spectrum to reconstruct the Higgs Boson mass.

Multiple vulnerabilities in Mitel Unify OpenStage and OpenScape phones allow a remote compromise in the unhardened default configuration and an elevation of privileges to become the root user.

This slide is prepared to give understanding of Blockchain Technology from the vary root to its leaf. You can build a strong foundation over it to become a professional Wev3 developer.