How-To Tutorials

article-image-navigation-mesh-generation

19 Dec 2014

9 min read

Navigation Mesh Generation

19 Dec 2014

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4378

Packt

19 Dec 2014

50 min read

Supervised learning

Packt

19 Dec 2014

50 min read

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2731

Packt

18 Dec 2014

11 min read

Securing your Twilio App

Packt

18 Dec 2014

11 min read

In this article, by Tim Rogers author of Twilio Best Practices, we'll see how to keep our Twilio account and applications (and ultimately credit) secure by: Enabling two-factor authentication on our Twilio account Verifying that requests to our application are really coming from Twilio Setting up a circuit breaker for our account and any subaccounts (For more resources related to this topic, see here.) Enabling two-factor authentication Twilio offers two-factor authentication functionality that we can enable on our account. This will give you much greater security if someone tries to break into your account following the something you know and something you have model. Apart from your password, Twilio will send you an SMS or call you when a login attempt is made, requiring you to enter a one-time password. Not only will this largely prevent malicious access to your account, but you'll also know that someone is attempting to access your account, and what's more, that they have your password. It's worth noting that, unsurprisingly, you can quite easily roll two-factor authentication functionality for your own application using Twilio's call and SMS functionality. Check out https://www.twilio.com/docs/howto/two-factor-authentication for help with getting started. There are two steps to enable two-factor authentication: First, you'll need to add a phone number. You can do this from your Twilio dashboard by clicking on the dropdown in the top-right corner, and then clicking on the first entry with your name and e-mail address. Next, click on Add phone number, and then enter your phone number. Twilio will send you an SMS (or alternatively, call you if you'd like), thereby ensuring that you own the phone number that you've provided. Once you've added and verified your phone number on your user profile, you'll need to set up two-factor authentication on your account(s). To get to the right place, click on Account Settings in the dropdown. If your login has been given access to another user's Twilio account, (that is, the account you access from the Switch Accounts menu option) an administrator on that account will need to repeat this process. From this page, you'll be able to choose between two different two-factor options (you can also disable the feature here): Once Per Computer: This will effectively make the device you're using trusted, which means that subsequent logins for the next 30 days won't require you to use your phone. Every log-in: Every time you try to log in to Twilio, you'll have to provide a one-time password from your phone. Once you're done, click on the Save Settings button at the bottom of your page to set up the two-factor authentication. There are a couple of other features you might want to check out on the Account Settings page. You can reset your API credentials if you accidentally reveal them and you can disable parts of Twilio's Request Inspector which might potentially store sensitive information from your application and require passwords in order to access recordings and media you send in MMS messages. Verifying that requests are from Twilio If parties other than Twilio are able to make requests to your application, they can potentially change and corrupt data or access sensitive information. Without authentication measures, if an attacker was able to guess the URLs of the endpoints on your application that Twilio hits with its webhooks, they could wreak havoc. For instance, they could spoof fake SMS messages so that they appear to come from users or they could access the private phones numbers of users they should only be able to call through a public line you provide. There are two routes you can take to prevent this, ensuring with a reasonable degree of certainty that a request genuinely comes from Twilio: Set up HTTP Basic Authentication Verify the signature of requests to ensure they're signed by Twilio HTTP Basic Authentication HTTP Basic Authentication simply allows you to require a username and password to access your web server's resources. If you're working with PHP, you'll want to set this up on the web server level. This is possible in most servers, including: Apache () Nginx () IIS () If you're not using one of these, you can be virtually certain anyway that this option will be available to you; simply have a look at its documentation or search the web. Alternatively, you can implement Basic Authentication in your PHP code using code along these lines. We'll store the username and password in environment variables for security: <?php if (!isset($_SERVER['PHP_AUTH_USER'])) { // The user didn't even try to authenticate, so sent 401 Unauthorized header('WWW-Authenticate: Basic realm="Twilio only!"'); header('HTTP/1.0 401 Unauthorized'); exit; } elseif ($_SERVER['PHP_AUTH_USER'] == $_ENV["TWILIO_USERNAME"] && $_SERVER['PHP_AUTH_PW'] == $_ENV["TWILIO_PASSWORD"]) { // The user authenticated successfully, so perform actions and output TwiML } else { // The user tried to authenticate, but didn't have the right credentials header('WWW-Authenticate: Basic realm="Twilio only!"'); header('HTTP/1.0 401 Unauthorized'); exit; } ?> Let's go through this bit by bit: If $_SERVER['PHP_AUTH_USER'] isn't set, then no username and password has been provided, so we respond with a 401 Unauthorized error (that is, a header request, and the user provides a username and password, as well as the WWW-Authenticate header), which will make browsers display Twilio only! in the login dialog. If the provided username and password do match what is stored in the TWILIO_USERNAME and TWILIO_PASSWORD environment variables respectively, then we perform actions that the request requires and respond with TwiML. If a username and password was provided, but didn't match those we expected, then we send our 401 error and associated headers again. When we're providing a URL to Twilio (for instance, when initiating a call via the REST API, or setting it for incoming calls or SMS messages from our Dashboard), we can set the username and password in this format: Verifying the signature Alternatively, instead of using a username and password, we can verify the cryptographic signature Twilio generates with its requests based upon our auth token which is sent in the X-Twilio-Signature header. The scheme for doing this is somewhat complicated (you can find it in full at https://www.twilio.com/docs/security#validating-requests) but fortunately, Twilio provides validation functionality in their API libraries alongside code samples. For this method of verification to be available, you'll need to serve your application over HTTPS with Transport Layer Security (TLS) enabled. In fact, you should always do this with your Twilio application, as a good security practice. Following the SSLv3 vulnerability discovered in October, 2014 known as POODLE, you'll want to double-check the security of any SSL configuration. See https://www.digitalocean.com/community/tutorials/how-to-protect-your-server-against-the-poodle-sslv3-vulnerability for details. In PHP, we'd execute the following: <?php // Load auth token from the TWILIO_AUTH_TOKEN environment variable $authToken = $_ENV['TWILIO_AUTH_TOKEN']; // You'll need to make sure the Twilio library is included, either by requiring // it manually or loading Composer's autoload.php $validator = new Services_Twilio_RequestValidator($authToken); $url = $_SERVER["SCRIPT_URI"]; $vars = $_GET; $signature = $_SERVER["HTTP_X_TWILIO_SIGNATURE"]; if ($validator->validate($signature, $url, $vars)) { // This request definitely came from Twilio, so continue onwards... } else { // Watch out - this is not a real request from Twilio. header('HTTP/1.0 401 Unauthorized'); } ?> Here, we instantiate a Services_Twilio_RequestValidator object from the API library with our auth token before passing in the requested URL, the request body ($_GET in this case, but for a POST request, this would be $_POST), and the signature. We then call the validator's validate method with these pieces of data, allowing it to generate the signature itself, and comparing it against what we received in the X-Twilio-Signature header. If it matches, the request is genuine, but if not, the request is spoofed and is not from Twilio. Building a circuit breaker Using Twilio's Usage Triggers allows us to build a circuit breaker. In short, this will let us know when one of our subaccounts passes certain amounts of usage, which will help us detect possible abuse of our account, as well as mistakes in our code. It can even help detect abuse if we were running a multitenant app (that is, offering Twilio-based services to our users). When our specified usage threshold is surpassed, Twilio will send a webhook to a URL of our choice. From this URL, we can perform a range of actions, whether that is sending ourselves an e-mail or even suspending the account in question. Here, we'll just run through a quick example of suspending an account if it spends more than $50 in one day. We'll set up our Usage Trigger using the Twilio dashboard. To do this, first log in, and then switch to the appropriate subaccount you'd like to set up the trigger for by clicking on your name in the top-right corner. Next, click on Subaccounts, and then click on the desired account. Next, click on Usage in the navigation bar, then click on Triggers underneath, and then click on the Create Usage Trigger button. Fill out the fields as shown in the following image. First, you'll need to click on the Trigger a webhook link on the right-hand side of the page where Send an email appears in the screenshot to set up a webhook, replacing the URL with one that would be accessible from a domain of your own, of course. We might also want to automate this process of setting up a usage trigger using the REST API. For example, we might want to automatically suspend a subaccount we've just created for a customer if their usage goes beyond reasonable limits. In order to do so, we'd do the same thing we did previously in PHP like this: <?php $accountSid = $_ENV['TWILIO_ACCOUNT_SID']; $authToken = $_ENV['TWILIO_AUTH_TOKEN']; $subaccountSid = '<the SID of the subaccount>'; // You'll need to make sure the Twilio library is included, either by requiring // it manually or loading Composer's autoload.php $client = new Services_Twilio($accountSid, $authToken); $account = $client->accounts->get($subaccountSid); $account->usage_triggers->create( 'totalprice', '+50', 'https://twiliobestpractices.com/path/to/trigger_action.php', array( 'Recurring' => 'daily', 'TriggerBy' => 'price', 'FriendlyName' => 'Suspend if uses more than $50 per day' ) ); ?> Both options do exactly the same thing. They create a trigger that will send a webhook to when more than $50 is spent by our subaccount on any one day. It's completely up to us what we do from the endpoint that receives the webhook. Anything we can program is possible, from suspending the account to calling an engineer to look into it. Here's some example code to go with the usage trigger we just set up that will automatically suspend the account once it goes over $50 spend in a day. In this code sample, we also verify the authenticity of the request, as we saw previously, making sure that this is a genuine Usage Trigger webhook from Twilio: <?php // Before starting, you'll need to require the Twilio PHP library // We'll load the SID of the subaccount that the trigger relates to and its // auth token from environment variables, but in reality, you're likely to be // loading them from a database of your users' details based on a passed-in ID, // or something along those lines. $subaccountSid = $_ENV['TWILIO_SUBACCOUNT_SID']; $subaccountAuthToken = $_ENV['TWILIO_SUBACCOUNT_AUTH_TOKEN']; $url = $_SERVER['SCRIPT_URI']; $signature = $_SERVER['HTTP_X_TWILIO_SIGNATURE']; $validator = new Services_Twilio_RequestValidator($subaccountAuthToken); if ($validator->validate($signature, $url, $_POST)) { $client = new Services_Twilio($subaccountSid, $subaccountAuthToken); $client->account->update(array('Status' => 'suspended')); } else { header('HTTP/1.0 401 Unauthorized'); } ?> We've shown you examples of doing all of this using the PHP library, but you can do it with any of Twilio's libraries . You can also do this directly with the REST API using a tool such as Postman. Summary In this article, we saw three helpful tips to keep your Twilio account and application secure: First, we enabled Two-Factor Authentication to keep our account secure, even if someone finds out our password. Next, we learned how to make sure that the requests your app receives genuinely come from Twilio, by either using the HTTP Basic Authentication or by verifying the cryptographic request signature. Finally, we set up alerts to inform us and take appropriate action when certain usage thresholds are reached using Twilio's Usage Triggers, helping protect your app from abuse and coding errors. Resources for Article: Further resources on this subject: Make phone calls, send SMS from your website using Twilio [article] Execution of Test Plans [article] Configuring Your Operating System [article]

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11235

How-To Tutorials

Packt

17 Dec 2014

29 min read

Enemy and Friendly AIs

Packt

17 Dec 2014

29 min read

0
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10220

Packt

17 Dec 2014

8 min read

The Arduino Mobile Robot

Packt

17 Dec 2014

8 min read

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9864

How-To Tutorials

Packt

17 Dec 2014

24 min read

Mastering Splunk: Lookups

Packt

17 Dec 2014

24 min read

0
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10411

Packt

16 Dec 2014

9 min read

Ridge Regression

Packt

16 Dec 2014

9 min read

In this article by Patrick R. Nicolas, the author of the book Scala for Machine Learning, we will cover the basics of ridge regression. The purpose of regression is to minimize a loss function, the residual sum of squares (RSS) being the one commonly used. The problem of overfitting can be addressed by adding a penalty term to the loss function. The penalty term is an element of the larger concept of regularization. (For more resources related to this topic, see here.) Ln roughness penalty Regularization consists of adding a penalty function J(w) to the loss function (or RSS in the case of a regressive classifier) in order to prevent the model parameters (or weights) from reaching high values. A model that fits a training set very well tends to have many features variable with relatively large weights. This process is known as shrinkage. Practically, shrinkage consists of adding a function with model parameters as an argument to the loss function: The penalty function is completely independent from the training set {x,y}. The penalty term is usually expressed as a power to function of the norm of the model parameters (or weights) wd. For a model of D dimension the generic Lp-norm is defined as follows: Notation Regularization applies to parameters or weights associated to an observation. In order to be consistent with our notation w0 being the intercept value, the regularization applies to the parameters w1 …wd. The two most commonly used penalty functions for regularization are L1 and L2. Regularization in machine learning The regularization technique is not specific to the linear or logistic regression. Any algorithm that minimizes the residual sum of squares, such as support vector machine or feed-forward neural network, can be regularized by adding a roughness penalty function to the RSS. The L1 regularization applied to the linear regression is known as the Lasso regularization. The Ridge regression is a linear regression that uses the L2 regularization penalty. You may wonder which regularization makes sense for a given training set. In a nutshell, L2 and L1 regularizations differ in terms of computation efficiency, estimation, and features selection (refer to the 13.3 L1 regularization: basics section in the book Machine Learning: A Probabilistic Perspective, and the Feature selection, L1 vs. L2 regularization, and rotational invariance paper available at http://www.machinelearning.org/proceedings/icml2004/papers/354.pdf). The various differences between the two regularizations are as follows: Model estimation: L1 generates a sparser estimation of the regression parameters than L2. For large non-sparse dataset, L2 has a smaller estimation error than L1. Feature selection: L1 is more effective in reducing the regression weights for features with high value than L2. Therefore, L1 is a reliable features selection tool. Overfitting: Both L1 and L2 reduce the impact of overfitting. However, L1 has a significant advantage in overcoming overfitting (or excessive complexity of a model) for the same reason it is more appropriate for selecting features. Computation: L2 is conducive to a more efficient computation model. The summation of the loss function and L2 penalty w2 is a continuous and differentiable function for which the first and second derivative can be computed (convex minimization). The L1 term is the summation of |wi|, and therefore, not differentiable. Terminology The ridge regression is sometimes called the penalized least squares regression. The L2 regularization is also known as the weight decay. Let's implement the ridge regression, and then evaluate the impact of the L2-norm penalty factor. Ridge regression The ridge regression is a multivariate linear regression with a L2 norm penalty term, and can be calculated as follows: The computation of the ridge regression parameters requires the resolution of the system of linear equations similar to the linear regression. Matrix representation of ridge regression closed form is as follows: I is the identity matrix and it is using the QR decomposition, as shown here: Implementation The implementation of the ridge regression adds L2 regularization term to the multiple linear regression computation of the Apache Commons Math library. The methods of RidgeRegression have the same signature as its ordinary least squares counterpart. However, the class has to inherit the abstract base class AbstractMultipleLinearRegression in the Apache Commons Math and override the generation of the QR decomposition to include the penalty term, as shown in the following code: class RidgeRegression[T <% Double](val xt: XTSeries[Array[T]], val y: DblVector, val lambda: Double) { extends AbstractMultipleLinearRegression with PipeOperator[Array[T], Double] { private var qr: QRDecomposition = null private[this] val model: Option[RegressionModel] = … … } Besides the input time series xt and the labels y, the ridge regression requires the lambda factor of the L2 penalty term. The instantiation of the class train the model. The steps to create the ridge regression models are as follows: Extract the Q and R matrices for the input values, newXSampleData (line 1) Compute the weights using the calculateBeta defined in the base class (line 2) Return the tuple regression weights calculateBeta and the residuals calculateResiduals private val model: Option[(DblVector, Double)] = { this.newXSampleData(xt.toDblMatrix) //1 newYSampleData(y) val _rss = calculateResiduals.toArray.map(x => x*x).sum val wRss = (calculateBeta.toArray, _rss) //2 Some(RegressionModel(wRss._1, wRss._2)) } The QR decomposition in the AbstractMultipleLinearRegression base class does not include the penalty term (line 3); the identity matrix with lambda factor in the diagonal has to be added to the matrix to be decomposed (line 4). override protected def newXSampleData(x: DblMatrix): Unit = { super.newXSampleData(x) //3 val xtx: RealMatrix = getX val nFeatures = xt(0).size Range(0, nFeatures).foreach(i => xtx.setEntry(i,i,xtx.getEntry(i,i) + lambda)) //4 qr = new QRDecomposition(xtx) } The regression weights are computed by resolving the system of linear equations using substitution on the QR matrices. It overrides the calculateBeta function from the base class: override protected def calculateBeta: RealVector = qr.getSolver().solve(getY()) Test case The objective of the test case is to identify the impact of the L2 penalization on the RSS value, and then compare the predicted values with original values. Let's consider the first test case related to the regression on the daily price variation of the Copper ETF (symbol: CU) using the stock daily volatility and volume as feature. The implementation of the extraction of observations is identical as with the least squares regression: val src = DataSource(path, true, true, 1) val price = src |> YahooFinancials.adjClose val volatility = src |> YahooFinancials.volatility val volume = src |> YahooFinancials.volume //1 val _price = price.get.toArray val deltaPrice = XTSeries[Double](_price .drop(1) .zip(_price.take(_price.size -1)) .map( z => z._1 - z._2)) //2 val data = volatility.get .zip(volume.get) .map(z => Array[Double](z._1, z._2)) //3 val features = XTSeries[DblVector](data.take(data.size-1)) val regression = new RidgeRegression[Double](features, deltaPrice, lambda) //4 regression.rss match { case Some(rss) => Display.show(rss, logger) …. The observed data, ETF daily price, and the features (volatility and volume) are extracted from the source src (line 1). The daily price change, deltaPrice, is computed using a combination of Scala take and drop methods (line 2). The features vector is created by zipping volatility and volume (line 3). The model is created by instantiating the RidgeRegression class (line 4). The RSS value, rss, is finally displayed (line 5). The RSS value, rss, is plotted for different values of lambda <= 1.0 in the following graph: Graph of RSS versus Lambda for Copper ETF The residual sum of squares decreased as λ increases. The curve seems to be reaching for a minimum around λ=1. The case of λ = 0 corresponds to the least squares regression. Next, let's plot the RSS value for λ varying between 1 and 100: Graph RSS versus large value Lambda for Copper ETF This time around RSS increases with λ before reaching a maximum for λ > 60. This behavior is consistent with other findings (refer to Lecture 5: Model selection and assessment, a lecture by H. Bravo and R. Irizarry from department of Computer Science, University of Maryland, in 2010, available at http://www.cbcb.umd.edu/~hcorrada/PracticalML/pdf/lectures/selection.pdf). As λ increases, the overfitting gets more expensive, and therefore, the RSS value increases. The regression weights can by simply outputted as follows: regression.weights.get Let's plot the predicted price variation of the Copper ETF using the ridge regression with different value of lambda (λ): Graph of ridge regression on Copper ETF price variation with variable Lambda The original price variation of the Copper ETF Δ = price(t+1)-price(t) is plotted as λ =0. The predicted values for λ = 0.8 is very similar to the original data. The predicted values for λ = 0.8 follows the pattern of the original data with reduction of large variations (peaks and troves). The predicted values for λ = 5 corresponds to a smoothed dataset. The pattern of the original data is preserved but the magnitude of the price variation is significantly reduced. The reader is invited to apply the more elaborate K-fold validation routine and compute precision, recall, and F1 measure to confirm the findings. Summary The ridge regression is a powerful alternative to the more common least squares regression because it reduces the risk of overfitting. Contrary to the Naïve Bayes classifiers, it does not require conditional independence of the model features. Resources for Article: Further resources on this subject: Differences in style between Java and Scala code [Article] Dependency Management in SBT [Article] Introduction to MapReduce [Article]

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0
6786

Packt

16 Dec 2014

9 min read

Adding Graded Activities

Packt

16 Dec 2014

9 min read

This article by Rebecca Barrington, author of Moodle Gradebook Second Edition, teaches you how to add assignments and set up how they will be graded, including how to use our custom scales and add outcomes for grading. (For more resources related to this topic, see here.) As with all content within Moodle, we need to select Turn editing on within the course in order to be able to add resources and activities. All graded activities are added through the Add an activity or resource text available within each section of within a Moodle course. This text can be found in the bottom right of each section after editing has been turned on. There are a number of items that can be graded and will appear within the Gradebook. Assignments are the most feature-rich of all the graded activities and have many options available in order to customize how assessments can be graded. They can be used to provide assessment information for students, store grades, and provide feedback. When setting up the assignment, we can choose for students to submit their work electronically—either through file submission or online text, or we can review the assessment offline and use only the grade and feedback features of the assignment. Adding assignments There are many options *within the assignments, and throughout this article we will set up a number of different assignments and you'll learn about some of their most useful features and options. Let's have a go at creating a range of assignments that are ready for grading. Creating an assignment with a scale The first assignment that we will add will *make use of the PMD scale Click on the Turn editing on button. Click on Add an activity or resource. Click on Assignment and then click on Add. In the Assignment name box, type in the name of the assignment (such as Task 1). In the Description box, provide some assignment details. In the Availability section, we need to disable the date options. We will not make use of these options, but they can be very useful. To disable the options, click on the tick next to the Enable text. However, details of these options have *been provided for future* reference. The Allow submissions from section* is mostly relevant when the assignment will be submitted electronically, as students won't be able to submit their work until the date and time indicated here. The Due date section* can be used to indicate when the assignment needs to be submitted by. If students electronically submit their assignment after the date and time indicated here, the submission date and time will be shown in red in order to notify the teacher that it was submitted past the due date. The Cut off date section* enables teachers to set an extension period after the due date where late submissions will continue to be accepted. In the* Submission types section, ensure *that the File submissions checkbox is enabled by adding a tick there. This will enable students to submit their assignment electronically. There are additional options that we can choose as well. With Maximum number of uploaded files, we can indicate how many files a student can upload. Keep this as 1. We can also determine the Maximum submission size option for each file using the drop-down list shown in the following screenshot: Within the Feedback types section, ensure that all options under the Feedback types *section are *selected. Feedback comments enables *us to provide written feedback along with the grade. Feedback files enables us *to upload a file in order to provide feedback to a student. Offline grading worksheet will *provide us with the option to download a .csv file that contains core information about the assignment, and this can be used to add grades and feedback while working offline. This completed .csv file can be uploaded and the grades will be added to the assignments within the Gradebook. In the Submission settings section, we have options related to how students will submit their assignment and how they will reattempt submission if required. If Require students click submit button is left as No, students will upload* their assignment* and it will be available *to the teacher for grading. If this option is changed to Yes, students can upload their assignment, but the teacher will see that it is in the draft form. Students will click on Submit to indicate that it is ready to be graded. Require that students accept the submission statement will provide students *with a statement that they need to agree to when they submit their assignment. The default statement is This assignment is my own work, except where I have acknowledged the use of works of other people. The submission statement can be changed by a site administrator by navigating to Site administration | plugins | Activity modules | Assignment settings. The Attempts reopened drop-down list* provides options for the status of the assignment after it has been graded. Students will only be able to resubmit their work when it is open. Therefore this setting will control when and if students are able to submit another version of their assignment. The options available to us are:Never: This option should be selected if students will not be able to submit another piece of work.Manually: This will enable anyone who has the role of a teacher to choose to reopen a submission that enables a student to submit their work again.Automatically until pass: This option works when a pass grade is set within the Gradebook. After grading, if the student is awarded the minimum pass *grade or higher, the submission *will remain closed in order to prevent any changes to the submission. However, if the assignment is graded lower than the assigned pass grade, the submission will automatically reopen in order to enable the student to submit the assignment again.Maximum attempts: The maximum *attempts allowed for this assignment will limit the number of times an assignment is reopened. For example, if this option is set to 3, then a student will only be able to submit their assignment three times. After they have submitted their assignment for a third time, they will not be allowed to submit it again. The default is unlimited, but it can be changed by clicking on the drop-down list. In the Submission settings section, ensure that the options for Require students click on submit button and Require that students accept the submission statement are set to Yes. Also, change the Attempts reopened to Automatically until passed. Within the Grade section, navigate to Grade | Type | Scale and choose the PMD scale. Select Use marking workflow by changing the drop-down list to Yes.Use marking workflow is a new feature of Moodle 2.6* that enables *the grading process to go through a range of stages in order to indicate that the marking is in progress or is complete, is being reviewed, or is ready for release to students. Click on* Save and return to course. Creating an online assignment with a number grade The next *assignment that we will create will have an online* text option that will have a maximum grade of 20. The following steps show you how to create an online assignment with a number grade: Enable editing by clicking on Turn editing on. Click on Add an activity or resource. Click on Assignment and then click on Add. In the Assignment name box, type in the name of the assignment (such as Task 2). In the Description box, provide the assignment details. In the Submission types section, ensure that Online text has a tick next to it. This will enable students to type directly into Moodle. When choosing this option, we can also set a maximum word limit by clicking on the tick box next to the Enable text. After enabling this option, we can add a number to the textbox. For this assignment, enable a word limit of 200 words. When using* online text* submission, we have an additional feedback option within the Feedback types section. Under the Comment inline text, click on No and switch to Yes to enable yourself to add written feedback for students within the written text submitted by students. In the Submission settings section, ensure that the options for Require students click submit button and Require that students accept the submission statement are set to Yes. Also, change Attempts reopened to Automatically until passed. Within the Grades section, navigate to Grade | Type | Point and ensure that Maximum points is set to 20. Click *on* Save and return to course. Creating an assignment including outcomes The next assignment that we will *create will add some of the Outcomes: Enable editing by clicking on Turn editing on. Click on Add an activity or resource. Click on Assignment and then click on Add. In the Assignment name box, type in the name of the assignment (such as Task 3). In the Description box, provide the assignment details. In the Submission types box, ensure that Online text and File submissions are selected. Set Maximum number of uploaded files to 2. In the Submission settings section, ensure that the options for Require students to click submit button and Require that students accept the submission statement are amended to Yes. Change Attempts reopened to Manually. Within the Grades section, navigate to Grade | Type | Point and Maximum points is set to 100. In the Outcomes *section, choose the outcomes as Evidence provided and Criteria 1 met. Scroll to the bottom of the screen and click on Save and return to course. Summary In this article, we added a range of assignments that made use of number and scale grades as well as added outcomes to an assignment. Resources for Article: Further resources on this subject: Moodle for Online Communities [article] What's New in Moodle 2.0 [article] Moodle 2.0: What's New in Add a Resource [article]

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2660

article-image-building-information-radiator-part-1

Andrew Fisher

16 Dec 2014

9 min read

Building an Information Radiator - Part 1

Andrew Fisher

16 Dec 2014

9 min read

Download the code files for this project here. I love lights; specifically, I love LEDs - which have been described to me as "catnip for geeks". LEDs are low powered but bright, which means they can be embedded into all sorts of interesting places and, when coupled with a network, can be used for all sorts of ambient display purposes. In this post, I'll show you how to build an "information radiator" with a bit of Python and some LEDs, which you can then use to make your own for your own personal needs. // An information radiator light showing the forecast temperature in Melbourne. An information radiator is so called as it radiates information outwards from (often) a fixed point so that it can be interpreted by an observer. More complex information can be encoded through the use of color, brightness, or frequency of lighting to encode more information. I'm going to show you how to build an ambient display that scrapes some data from a weather service and then display it using colored light to indicate the forecasted temperature. This is quite a simple example, but by the end of this two-part post series, you will be able to change your information radiator to consider rain or multiple elements, or even point to something that is important to you. Bill of materials Item Description Cost Ethernet Arduino The Freetronics EtherTen is excellent, but an Arduino Uno with an Ethernet shield works too. $60 RGB LED The light discs from DFRobot are great as they produce a lot of light. $10 Computer This is needed to run the Python script to check the weather. Wire Red, green, blue, and white is ideal, but anything you have available is fine. $2 Light fitting Anything that diffuses light will be interesting. $1+ Tools required These common tools will come in handy: Soldering iron Wire strippers Design You don't want the light attached to the computer all the time - what's the point of a light if you can just look up the weather on Google? The device will connect to the network and exist somewhere visible, and then the processing can run on a mini server somewhere (such as a Raspberry Pi) and just send the device messages when needed. So, the system design looks like this: The microcontroller looks after the LED and exposes a network interface. A Python script runs periodically on the server to check the weather forecast, get the data, and then send a message to the Arduino. Building the light The build of the light is quite straightforward. Cut four pieces of wire about 6 inches long (personal preference) and solder them to the four connections on the light disk. // Light disc with wires soldered on. Strip 5mm of wire from the other end and wire the light disk to the Arduino in the following way: R to pin 5 G to pin 6 B to pin 9 Depending on the version of the light disc you have, wire GND to GND or 5V to 5V. The specifics are labelled on the disc itself, and the newer discs are GND. // Light disc wired into Arduino. That's it! You're all done electronics-wise. Plug in an Ethernet cable and ensure you have 7-20V power supplied from a power pack to the Arduino. Programming the Arduino If you have never programmed an Arduino before, I suggest this tutorial as an excellent starting point. I'm going to assume you have got the Arduino IDE installed on your computer and you can upload sketches. First, you need to test your wiring. The following Arduino code will cycle through combinations of colors for about 1 second each. It will print the color to the serial console as well, so you can observe it with the serial monitor: #define RED 5 #define GREEN 6 #define BLUE 9 #define MAX_COLOURS 8 #define GND true // change this to false if 5V type char* colours[] = {"Off", "red", "green", "yellow", "blue", "magenta", "cyan", "white"}; uint8_t current_colour = 0; void setup() { Serial.begin(9600); Serial.println("Testing lights"); pinMode(RED, OUTPUT); pinMode(GREEN, OUTPUT); pinMode(BLUE, OUTPUT); if (GND) { digitalWrite(RED, LOW); digitalWrite(GREEN, LOW); digitalWrite(BLUE, LOW); } else { digitalWrite(RED, HIGH); digitalWrite(GREEN, HIGH); digitalWrite(BLUE, HIGH); } } void loop () { Serial.print("Current colour: "); Serial.println(colours[current_colour]); if (GND) { digitalWrite(RED, current_colour & 1); digitalWrite(GREEN, current_colour & 2); digitalWrite(BLUE, current_colour & 4); } else { digitalWrite(RED, !(bool)(current_colour & 1)); digitalWrite(GREEN, !(bool)(current_colour & 2)); digitalWrite(BLUE, !(bool)(current_colour & 4)); } if ((++current_colour) >= MAX_COLOURS) current_colour=0; delay(1000); } Notably, there is a flag to flip (#define GND true | false) depending on whether your light disc uses GND or 5V. All this does is reverse the bit-shifting logic (on the GND disc, the light goes on when the pin goes HIGH, but on the 5V disc, the light goes on when the pin goes LOW). If the colors are muddled, you have probably just connected a wire to the wrong pin; just flip them over and it should be fine. If you aren't seeing any light, check your connections and ensure you are getting power to the light disk. The next thing to do is write the sketch that will take messages from the network and update the light. To do this, we need to establish a protocol. There are many ways to define this, but for simplicity, a text protocol like JSON works sufficiently well. Each message will look like this: {r:val, g:val, b:val} In each case, val is an unsigned byte, so will be in the range 0-255: // Adapted from generic web server example as part of IDE created by David Mellis and Tom Igoe. #include "Arduino.h" #include <Ethernet.h> #include <SPI.h> #include <string.h> #include <stdlib.h> #define DEBUG false // <1> // Enter a MAC address and IP address for your controller below. // The IP address will be dependent on your local network: byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xAE }; byte ip[] = { <PUT YOUR IP HERE AS COMMA BYTES> }; //eg 192,168,0,100 byte gateway[] = { <PUT YOUR GW HERE AS COMMA BYTES}; // eg 192,168,0,1 byte subnet[] = { <PUT YOUR SUBNET HERE>}; //eg 255,255,255,0 // Initialize the Ethernet server library // with the IP address and port you want to use (in this case telnet) EthernetServer server(23); #define BUFFERLENGTH 255 // these are the pins you wire each LED to. #define RED 5 #define GREEN 6 #define BLUE 9 #define GND true // change this to false if 5V type, true if GND type light disc void setup() { Ethernet.begin(mac, ip, gateway, subnet); server.begin(); #ifdef DEBUG Serial.begin(9600); Serial.println("Awaiting connection"); #endif } void loop() { char buffer[BUFFERLENGTH]; int index = 0; // Listen EthernetClient client = server.available(); if (client) { #ifdef DEBUG Serial.println("Got a client"); #endif // reset the input buffer index = 0; while (client.connected()) { if (client.available()){ char c = client.read(); // if it's not a new line, then add it to the buffer <2> if (c != 'n' && c != 'r') { buffer[index] = c; index++; if (index > BUFFERLENGTH) index = BUFFERLENGTH -1; continue; } else { buffer[index] = ' '; } // get the message string for processing String msgstr = String(buffer); // get just the bits we want between the {} msgstr = msgstr.substring(msgstr.lastIndexOf('{')+1, msgstr.indexOf('}', msgstr.lastIndexOf('{'))); msgstr.replace(" ", ""); msgstr.replace("'", ""); #ifdef DEBUG Serial.println("Message:"); Serial.println(msgstr); #endif // rebuild the buffer with just the URL msgstr.toCharArray(buffer, BUFFERLENGTH); // iterate over the tokens of the message - assumed flat. <3> char *p = buffer; char *str; while ((str = strtok_r(p, ",", &p)) != NULL) { #ifdef DEBUG Serial.println(str); #endif char *tp = str; char *key; char *val; // get the key key = strtok_r(tp, ":", &tp); val = strtok_r(NULL, ":", &tp); #ifdef DEBUG Serial.print("Key: "); Serial.println(key); Serial.print("val: "); Serial.println(val); #endif // <4> if (GND) { if (*key == 'r') analogWrite(RED, atoi(val)); if (*key == 'g') analogWrite(GREEN, atoi(val)); if (*key == 'b') analogWrite(BLUE, atoi(val)); } else { if (*key == 'r') analogWrite(RED, 255-atoi(val)); if (*key == 'g') analogWrite(GREEN, 255-atoi(val)); if (*key == 'b') analogWrite(BLUE, 255-atoi(val)); } } break; } } delay(10); // give client time to send any data back client.stop(); } } The most notable parts of the code are as follows: You add your own network settings in here This text parser just adds text to a buffer until a n arrives As this protocol is simple, I use a string tokenizer to break up the message into its constituent pieces as key-value pairs Use the RGB values to set the appropriate level on the PWM pins (noting polarity reversal for GND vs 5V light discs) To test the code, upload the sketch, ensure your Ethernet cable is plugged in, and attempt to connect to the device: telnet <ip> 23 This should return something like the following: Trying 10.0.1.91... Connected to 10.0.1.91. Escape character is '^]'. Now, enter: {r:200,g:0, b:0} <enter> If the light changes to red, then everything is working - time to get some data. If not, check your code and make sure the messages are being interpreted properly (plug in your computer to use the serial debugger to watch the messages). Play around with changing the colors of your light by sending different values to the device. In the Part 2 post, I’ll explain how to scrape the weather data we want and use that to update the light periodically. About the Author Andrew Fisher is a creator (and destroyer) of things that combine mobile web, ubicomp, and lots of data. He is a programmer, interaction researcher, and CTO at JBA, a data consultancy in Melbourne, Australia. He can be found on Twitter at @ajfisher.

0
0
2523

How-To Tutorials

Packt

16 Dec 2014

7 min read

Role of AngularJS

Packt

16 Dec 2014

7 min read

This article by Sandeep Kumar Patel, author of Responsive Web Design with AngularJS we will explore the role of AngularJS for responsive web development. Before going into AngularJS, you will learn about responsive "web development in general. Responsive" web development can be performed "in two ways: Using the browser sniffing approach Using the CSS3 media queries approach (For more resources related to this topic, see here.) Using the browser sniffing approach When we view" web pages through our browser, the browser sends a user agent string to the server. This string" provides information like browser and device details. Reading these details, the browser can be redirected to the appropriate view. This method of reading client details is known as browser sniffing. The browser string has a lot of different information about the source from where the request is generated. The following diagram shows the information shared by the user string: Details of the parameters" present in the user agent string are as follows: Browser name: This" represents the actual name of the browser from where the request has originated, for example, Mozilla or Opera Browser version: This represents" the browser release version from the vendor, for example, Firefox has the latest version 31 Browser platform: This represents" the underlying engine on which the browser is running, for example, Trident or WebKit Device OS: This represents" the operating system running on the device from where the request has originated, for example, Linux or Windows Device processor: This represents" the processor type on which the operating system is running, for example, 32 or 64 bit A different browser string is generated based on the combination of the device and type of browser used while accessing a web page. The following table shows examples of browser "strings: Browser Device User agent string Firefox Windows desktop Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Firefox/31.0 Chrome OS X 10 desktop Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.66 Safari/537.36 Opera Windows desktop Opera/9.80 (Windows NT 6.0) Presto/2.12.388 Version/12.14 Safari OS X 10 desktop Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/537.13+ (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2 Internet Explorer Windows desktop Mozilla/5.0 (compatible; MSIE 10.6; Windows NT 6.1; Trident/5.0; InfoPath.2; SLCC1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727) 3gpp-gba UNTRUSTED/1.0 AngularJS has features like providers or services which can be most useful for this browser user-agent sniffing and a redirection approach. An AngularJS provider can be created that can be used in the configuration in the routing module. This provider can have reusable properties and reusable methods that can be used to identify the device and route the specific request to the appropriate template view. To discover more about user agent strings on various browser and device combinations, visit http://www.useragentstring.com/pages/Browserlist/. CSS3 media queries approach CSS3 brings a "new horizon to web application development. One of the key features" is media queries to develop a responsive web application. Media queries uses media types and features as "deciding parameters to apply the style to the current web page. Media type CSS3 media queries" provide rules for media types to have different styles applied to a web page. In the media queries specification, media types that should be supported by the implemented browser are listed. These media types are as follows: all: This is used" for all media type devices aural: This is "used for speech and sound synthesizers braille: This is used "for braille tactile feedback devices embossed: This" is used for paged braille printers handheld: This is "used for small or handheld devices, for example, mobile print: This" is used for printers, for example, an A4 size paper document projection: This is" used for projection-based devices, such as a projector screen with a slide screen: This is "used for computer screens, for example, desktop and "laptop screens tty: This is" used for media using a fixed-pitch character grid, such as teletypes and terminals tv: This is used "for television-type devices, for example, webOS "or Android-based television A media rule can be declared using the @media keyword with the specific type for the targeted media. The following code shows an example of the media rule usage, where the background body color" is black and text is white for the screen type media, and background body color is white and text is black for the printer media type: @media screen { body { background:black; color:white; } } @media print{ body { background:white; color:black; } } An external style "sheet can be downloaded and applied to the current page based on the media type with the HTML link tag. The following code uses the link type in conjunction with media type: <link rel='stylesheet' media='screen' href='<fileName.css>' /> To learn more about" different media types,visit https://developer.mozilla.org/en-US/docs/Web/CSS/@media#Media_types. Media feature Conditional styles can be "applied to a page based on different features of a device. The features that are "supported by CSS3 media queries to apply styles are as follows: color: Based on the" number of bits used for a color component by the device-specific style sheet, this can be applied to a page. color-index: Based "on the color look up, table styles can be applied "to a page. aspect-ratio: Based "on the aspect ratio, display area style sheets can be applied to a page. device-aspect-ratio: Based "on the device aspect ratio, styles can be applied to a page. device-height: Based "on device height, styles can be applied to a page. "This includes the entire screen. device-width: Based "on device width, styles can be applied to a page. "This includes the entire screen. grid: Based "on the device type, bitmap or grid, styles can be applied "to a page. height: Based on" the device rendering area height, styles can be used "to a page. monochrome: Based on" the monochrome type, styles can be applied. "This represents the number of bits used by the device in the grey scale. orientation: Based" on the viewport mode, landscape or portrait, styles can be applied to a page. resolution: Based" on the pixel density, styles can be applied to a page. scan: Based on the "scanning type used by the device for rendering, styles can be applied to a page. width: Based "on the device screen width, specific styles can be applied. The following" code shows some examples" of CSS3 media queries using different device features for conditional styles used: //for screen devices with a minimum aspect ratio 0.5 @media screen and (min-aspect-ratio: 1/2) { img { height: 70px; width: 70px; } } //for all device in portrait viewport @media all and (orientation: portrait) { img { height: 100px; width: 200px; } } //For printer devices with a minimum resolution of 300dpi pixel density @media print and (min-resolution: 300dpi) { img { height: 600px; width: 400px; } } To learn more" about different media features, visit https://developer.mozilla.org/en-US/docs/Web/CSS/@media#Media_features. Summary In this chapter, you learned about responsive design and the SPA architecture. "You now understand the role of the AngularJS library when developing a responsive application. We quickly went through all the important features of AngularJS with the coded syntax. In the next chapter, you will set up your AngularJS application and learn to create dynamic routing-based on the devices. Resources for Article: Further resources on this subject: Best Practices for Modern Web Applications [article] Important Aspect of AngularJS UI Development [article] A look into responsive design frameworks [article]

0
23
41358

How-To Tutorials

Packt

16 Dec 2014

7 min read

Overview of Chips

Packt

16 Dec 2014

7 min read

In this article by Olliver M. Schinagl, author of Getting Started with Cubieboard, we will overview various development boards and compare a few popular ones to help you choose a board tailored to your requirements. In the last few years, ARM-based Systems on Chips (SoCs) have become immensely popular. Compared to the regular x86 Intel-based or AMD-based CPUs, they are much more energy efficient and still performs adequately. They also incorporate a lot of peripherals, such as a Graphics Processor Unit (GPU), a Video Accelerator (VPU), an audio controller, various storage controllers, and various buses (I2C and SPI), to name a few. This immensely reduces the required components on a board. With the reduction in the required components, there are a few obvious advantages, such as reduction in the cost and, consequentially, a much easier design of boards. Thus, many companies with electronic engineers are able to design and manufacture these boards cheaply. (For more resources related to this topic, see here.) So, there are many boards; does that mean there are also many SoCs? Quite a few actually, but to keep the following list short, only the most popular ones are listed: Allwinner's A-series Broadcom's BCM-series Freescale's i.MX-series MediaTek's MT-series Rockchip's RK-series Samsung's Exynos-series NVIDIA's Tegra-series Texas Instruments' AM-series and OMAP-series Qualcomm's APQ-series and MSM-series While many of the potential chips are interesting, Allwinner's A-series of SoCs will be the focus of this book. Due to their low price and decent availability, quite a few companies design development boards around these chips and sell them at a low cost. Additionally, the A-series is, presently, the most open source friendly series of chips available. There is a fully open source bootloader, and nearly all the hardware is supported by open source drivers. Among the A-series of chips, there are a few choices. The following is the list of the most common and most interesting devices: A10: This is the first chip of the A-series and the best supported one, as it has been around for long. It is able to communicate with the outside world over I2C, SPI, MMC, NAND, digital and analog video out, analog audio out, SPDIF, I2S, Ethernet MAC, USB, SATA, and HDMI. This chip initially targeted everything, such as phones, tablets, set-top boxes, and mini PC sticks. For its GPU, it features the MALI-400. A10S: This chip followed the A10; it focused mainly on the PC stick market and left out several parts, such as SATA and analog video in/out, and it has no LCD interface. These parts were left out to reduce the cost of the chip, making it interesting for cheap TV sticks. A13: This chip was introduced more or less simultaneously with the A10S for primary use in tablets. It lacked SATA, Ethernet MAC, and also HDMI, which reduced the chip's cost even more. A20: This chip was introduced way after the others and hence it was pin-compatible to the A10 intended to replace it. As the name hints, the A20 is a dual-core variant of the A10. The ARM cores are slightly different; Cortex-A7 has been used in the A10 instead of Cortex-A8. A23: This chip was introduced after the A31 and A31S and is reasonably similar to the A31 in its design. It features a dual-core Cortex-A7 design and is intended to replace the A13. It is mainly intended to be used in tablets. A31: This chip features four Cortex-A7 cores and generally has all the connections that the A10 has. It is, however, not popular within the community because it features a PowerVR GPU that, until now, has seen no community support at all. Additionally, there are no development boards commonly available for this chip. A31S: This chip was released slightly after the A31 to solve some issues with the A31. There are no common development boards available. Choosing the right development board Allwinner's A-series of SoCs was produced and sold so cheaply that many companies used these chips in their products, such as tablets, set-top boxes, and eventually, development boards. Before the availability of development boards, people worked on and with tablets and set-top boxes. The most common and popular boards are from Cubietech and Olimex, in part because both companies handed out development boards to community developers for free. Olimex Olimex has released a fair amount of different development boards and peripherals. A lot of its boards are open source hardware with schematics and layout files available, and Olimex is also very open source friendly. You can see the Olimex board in the following image: Olimex offers the A10-OLinuXino-LIME, an A10-based micro board that is marketed to compete with the famous Raspberry Pi price-wise. Due to its small size, it uses less standard, 1.27 mm pitch headers for the pins, but it has nearly all of these pins exposed for use. You can see the A10-OLinuXino-LIME board in the following image: The Olimex OLinuXino series of boards is available in the A10, A13, and A20 flavors and has more standard, 2.54 mm pitch headers that are compatible with the old IDE and serial connectors. Olimex has various sensors, displays, and other peripherals that are also compatible with these headers. Cubietech Cubietech was formed by previous Allwinner employees and was one of the first development boards available using the Allwinner SoC. While it is not open source hardware, it does offer the schematics for download. Cubietech released three boards: the Cubieboard1, the Cubieboard2, and the Cubieboard3—also known as the Cubietruck. Interfacing with these boards can be quite tricky, as they use 2 mm pitch headers that might be hard to find in Europe or America. You can see the Cubietech board in the following image: Cubieboard1 and Cubieboard2 use identical boards; the only difference is that A20 is used instead of A10 in Cubieboard2. These boards only have a subset of the pins exposed. You can see the Cubietruck board in the following image: Cubietruck is quite different but a well-designed A20 board. It features everything that the previous boards offer, along with Gigabit Ethernet, VGA, Bluetooth, Wi-Fi, and an optical audio out. This does come at the cost that there are fewer pins to keep the size reasonably small. Compared to Raspberry Pi or LIME, it is almost double the size. Lemaker Lemaker made a smart design choice when releasing its Banana Pi board. It is an Allwinner A20-based board but uses the same board size and connector placement as Raspberry Pi and hence the name Banana Pi. Because of this, many of those Raspberry Pi cases could fit the Banana Pi and even shields will fit. Software-wise, it is quite different and does not work when using Raspberry Pi image files. Nevertheless, it features composite video out, stereo audio out, HDMI out Gigabit Ethernet, two USB ports, one USB OtG port, CSI out and LVDS out, and a handful of pins. Also available are a LiPo battery connector and a SATA connector and two buttons, but those might not be accessible on a lot of standard cases. See the following image for the topside of the Banana Pi: Itead and Olimex Itead and Olimex both offer an interesting board, which is worth mentioning separately. The Iteaduino Plus and the Olimex A20-SoM are quite interesting concepts; the computing module, which is a board with the SoC, memory, and flash, which are plugin modules, and a separated baseboard. Both of them sell a very complete baseboard as open source hardware, but anybody can design their own baseboard and buy the computing module. You can see the following board by Itead: Refer to the following board by Olimex: Additional hardware While a development board is a key ingredient, there are several other items that are also required. A power supply, for example, is not always supplied and does have some considerations. Also, additional hardware is required for the initial communication and to debug. Summary In this article, you looked at the additional hardware and a few extra peripherals that will help you understand the stuff you require for your projects. Resources for Article: Further resources on this subject: Home Security by BeagleBone [article] Mobile Devices [article] Making the Unit Very Mobile – Controlling the Movement of a Robot with Legs [article]

0
0
8868

How-To Tutorials

article-image-how-make-game-using-only-free-tools

Ellison Leao

16 Dec 2014

3 min read

How to Make a Game Using Only Free Tools

Ellison Leao

16 Dec 2014

3 min read

Being an independent game developer is never easy. Many developers do not have enough money or sponsorship to buy great game development tools to continue creating great games. If you are starting a career in game development or if you are already a game developer who doesn't want to spend money on licenses,in this post we will examine how to create great games using only free tools. There are some game engines with some free licenses available, which are limited but very powerful. Here are some of them: GameMaker GameMaker, by YoYo Studios, is a very powerful tool that doesn't require a lot of programming skills, since it uses a proper script language called GML, which has a very small learning curve. The free version only exports to Windows. To learn more about it, go to their website: https://www.yoyogames.com/studio. Unity Unity3D is the most famous game development tool these days. With Unity you can create games from 2D platformers to 3D FPS with a few drag-and-drop elements and some scripting. And speaking about scripting, you can create Unity scripts using C#, UnityScript (a Unity version of JavaScript), or Boo. You can use most of the engine features, but if you want to make some money with your games, you can only use the free version if your game annual income does not exceed $100,000. If so, you will need to buy a Pro license. Construct 2 Similar to the GameMaker tool, Construct 2 by Scirraprovidessome abstraction layers for non-programmers and makes it easy and quick to deliver a game. The free version can export to the Windows Store, the Chrome Web Store, and Facebook. But if you are a good programmer who likes a bit of a challenge, there are several tools for you. Here are some frameworks to get you started: Phaser Phaser is an open source HTML5 framework, which provides some nice features, such as WebGL and canvas renders, a physics, particles, animation and camera systems, and more. It also supports Typescript for development. Monogame Monogame is the open source version of the XNA 4 framework. The main goal is to let Monogame users build their games for many platforms, such as iOS, Android, Mac OS X, Linux, and Windows 8. FlashPunk FlashPunk is a framework written in ActionScript3 that helps you build 2D flash games. It has anything that a game needs, from collision support, audio and graphics system, to a live debugger that helps you fix bugs. These tools are just a sample of many other tools that exist out there. We've created a GitHub repo, gathering information from many places and listing a lot of game development resources that you can use to enhance your game development experience. It covers many types of tools, like 3D tools to render terrains, audio tools to make sound effect and soundtracks, free assets websites and more. You can find the list by clicking here. About the Author Ellison Leão (@ellisonleao) is a passionate software engineer with more than 6 years of experience in web projects. He is a contributor to the MelonJS framework and other open source projects. When he is not writing games, he loves to play drums.

0
0
7177

How-To Tutorials

article-image-how-to-auto-scale-your-cloud-with-saltstack

Nicole Thomas

15 Dec 2014

10 min read

How to Auto-Scale Your Cloud with SaltStack

Nicole Thomas

15 Dec 2014

10 min read

0
0
11265

article-image-how-to-build-a-koa-web-application-part-1

Christoffer Hallas

15 Dec 2014

8 min read

How to Build a Koa Web Application - Part 1

Christoffer Hallas

15 Dec 2014

8 min read

You may be a seasoned or novice web developer, but no matter your level of experience, you must always be able to set up a basic MVC application. This two part series will briefly show you how to use Koa, a bleeding edge Node.js web application framework to create a web application using MongoDB as its database. Koa has a low footprint and tries to be as unbiased as possible. For this series, we will also use Jade and Mongel, two Node.js libraries that provide HTML template rendering and MongoDB model interfacing, respectively. Note that this series requires you to use Node.js version 0.11+. At the end of the series, we will have a small and basic app where you can create pages with a title and content, list your pages, and view them. Let’s get going! Using NPM and Node.js If you do not already have Node.js installed, you can download installation packages at the official Node.js website, http://nodejs.org. I strongly suggest that you install Node.js in order to code along with the article. Once installed, Node.js will add two new programs to your computer that you can access from your terminal; they’re node and npm. The first program is the main Node.js program and is used to run Node.js applications, and the second program is the Node Package Manager and it’s used to install Node.js packages. For this application we start out in an empty folder by using npm to install four libraries: $ npm install koa jade mongel co-body Once this is done, open your favorite text editor and create an index.js file in the folder in which we will now start our creating our application. We start by using the require function to load the four libraries we just installed: var koa = require('koa'); var jade = require('jade'); var mongel = require('mongel'); var parse = require(‘co-body'); This simply loads the functionality of the libraries into the respective variables. This lets us create our Page model and our Koa app variables: var Page = mongel('pages', ‘mongodb://localhost/app'); var app = koa(); As you can see, we now use the variables mongel and koa that we previously loaded into our program using require. To create a model with mongel, all we have to do is give the name of our MongoDB collection and a MongoDB connection URI that represents the network location of the database; in this case we’re using a local installation of MongoDB and a database called app. It’s simple to create a basic Koa application, and as seen in the code above, all we do is create a new variable called app that is the result of calling the Koa library function. Middleware, generators, and JavaScript Koa uses a new feature in JavaScript called generators. Generators are not widely available in browsers yet except for some versions of Google Chrome, but since Node.js is built on the same JavaScript as Google Chrome it can use generators. The generators function is much like a regular JavaScript function, but it has a special ability to yield several values along with the normal ability of returning a single value. Some expert JavaScript programmers used this to create a new and improved way of writing asynchronous code in JavaScript, which is required when building a networked application such as a web application. The generators function is a complex subject and we won’t cover it in detail. We’ll just show you how to use it in our small and basic app. In Koa, generators are used as something called middleware, a concept that may be familiar to you from other languages such as Ruby and Python. Think of middleware as a stack of functions through which an HTTP request must travel in order to create an appropriate response. Middleware should be created so that the functionality of a given middleware is encapsulated together. In our case, this means we’ll be creating two pieces of middleware: one to create pages and one to list pages or show a page. Let’s create our first middleware: app.use(function* (next) { … }); As you can see, we start by calling the app.use function, which takes a generator as its argument, and this effectively pushes the generator into the stack. To create a generator, we use a special function syntax where an asterisk is added as seen in the previous code snippet. We let our generator take a single argument called next, which represents the next middleware in the stack, if any. From here on, it is simply a matter of checking and responding to the parameters of the HTTP request, which are accessible to us in the Koa context. This is also the function context, which in JavaScript is the keyword this, similar to other languages and the keyword self: if (this.path != '/create') { yield next; return } Since we’re creating some middleware that helps us create pages, we make sure that this request is for the right path, in our case, /create; if not, we use the yield keyword and the next argument to pass the control of the program to the next middleware. Please note the return keyword that we also use; this is very important in this case as the middleware would otherwise continue while also passing control to the next middleware. This is not something you want to happen unless the middleware you’re in will not modify the Koa context or HTTP response, because subsequent middleware will always expect that they’re now in control. Now that we have checked that the path is correct, we still have to check the method to see if we’re just showing the form to create a page, or if we should actually create a page in the database: if (this.method == 'POST') { var body = yield parse.form(this); var page = yield Page.createOne({ title: body.title, contents: body.contents }); this.redirect('/' + page._id); return } else if (this.method != 'GET') { this.status = 405; this.body = 'Method Not Allowed'; return } To check the method, we use the Koa context again and the method attribute. If we’re handling a POST request we now know how to create a page, but this also means that we must extract extra information from the request. Koa does not process the body of a request, only the headers, so we use the co-body library that we downloaded early and loaded in as the parse variable. Notice how we yield on the parse.form function; this is because this is an asynchronous function and we have to wait until it is done before we continue the program. Then we proceed to use our mongel model Page to create a page using the data we found in the body of the request, again this is an asynchronous function and we use yield to wait before we finally redirect the request using the page’s database id. If it turns out the method was not POST, we still want to use this middleware to show the form that is actually used to issue the request. That means we have to make sure that the method is GET, so we added an else if statement to the original check, and if the request is neither POST or GET we respond with an HTTP status 405 and the message Method Not Allowed, which is the appropriate response for this case. Notice how we don’t yield next; this is because the middleware was able to determine a satisfying response for the request and it requires no further processing. Finally, if the method was actually POST, we use the Jade library that we also installed using npm to render a create.jade template in HTML: var html = jade.renderFile('create.jade'); this.body = html; Notice how we set the Koa context’s body attribute to the rendered HTML from Jade; all this does is tell Koa that we want to send that back to the browser that sent the request. Wrapping up You are well on your way to creating your Koa app. In Part 2 we will implement Jade templates and list and view pages. Ready for the next step? Read Part 2 here. Explore all of our top Node.js content in one place - visit our Node.js page today! About the author Christoffer Hallas is a software developer and entrepreneur from Copenhagen, Denmark. He is a computer polyglot and contributes to and maintains a number of open source projects. When not contemplating his next grand idea (which remains an idea) he enjoys music, sports, and design of all kinds. Christoffer can be found on GitHub as hallas and at Twitter as @hamderhallas.

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article-image-how-to-run-hadoop-on-google-cloud-1

Robi Sen

15 Dec 2014

4 min read

How to Run Hadoop on Google Cloud – Part 1

Robi Sen

15 Dec 2014

4 min read

Setting up and working with Hadoop can sometimes be difficult. Furthermore, most people with limited resources develop on Hadoop instances on Virtual Machines locally or on minimal hardware. The problem with this is that Hadoop is really designed to run on many machines in order to realize its full capabilities. In this two part series of posts, we will show you how you can get started with Hadoop in the cloud with Google services quickly and relatively easily. Getting Started The first thing you need in order to follow along is a Google account. If you don’t have a Google account, you can sign up here: https://accounts.google.com/SignUp. Next, you need to create a Google Compute and Google Cloud storage enabled project via the Google Developers Console. Let’s walk through that right now. First go to the Developer Console and log in using your Google account. You will need your credit card as part of this process; however, to complete this two part post series, you will not need to spend any money. Once you have logged in, you should see something like what is shown in Figure 1. Figure 1: Example view of Google Developers Console Now select Create Project. This will pop up the create new project windows, as shown in Figure 2. In the project name field, go ahead and name your project HadoopTutorial. For the Project ID, Google will assign you a random project ID or you can try to select your own. Whatever your project ID is, just make note of it since we will be using it later. If, however, you forget your project ID, you can just come back to the Google console to look it up. You do not need to select the first checkbox shown in Figure 2, but go ahead and check the second checkbox, which is the terms of service. Now select Create. Figure 2: New Project window When you select Create, be prepared for a small delay as Google builds your project. When it is done, you should see a screen like that shown in Figure 3. Figure 3: Project Dashboard Now click on Enable an API. You should now see the APIs screen. Make sure you check to see whether the Google Cloud Storage and Google Cloud Storage JSON API options are enabled, that is, showing a green ON button. Now scroll down and find the Google Compute Engine and select the OFF button to enable it like the one shown in Figure 4. If you don’t have a payment account set up on Google, you will be asked to do that now and put in a valid credit card. Once that is done, you can go back and enable the Google Compute Engine. Figure 4: Setting up your Google APIs You should now have your Google developer account up and running. In the next post, I will walk you through the installation of the Google Cloud SDK and setting up Hadoop via Windows and Cygwin. Read part 2 here. Want more Hadoop content? Check out our dynamic Hadoop page, updated with our latest titles and most popular content. About the author Robi Sen, CSO at Department 13, is an experienced inventor, serial entrepreneur, and futurist whose dynamic twenty-plus year career in technology, engineering, and research has led him to work on cutting edge projects for DARPA, TSWG, SOCOM, RRTO, NASA, DOE, and the DOD. Robi also has extensive experience in the commercial space, including the co-creation of several successful start-up companies. He has worked with companies such as Under Armour, Sony, CISCO, IBM, and many others to help build out new products and services. Robi specializes in bringing his unique vision and thought process to difficult and complex problems, allowing companies and organizations to find innovative solutions that they can rapidly operationalize or go to market with.

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