Build a Node.js Chat Application with Socket.IO on a Windows Azure Cloud Service

Socket.IO provides realtime communication between between your node.js server and clients. This tutorial will walk you through hosting a socket.IO based chat application on Windows Azure. For more information on Socket.IO, see http://socket.io/.

A screenshot of the completed application is below:

Create a Cloud Service Project

The following steps create the cloud service project that will host the Socket.IO application.

1. From the Start Menu or Start Screen, search for Windows Azure PowerShell. Finally, right-click Windows Azure PowerShell and select Run As Administrator.

   

   Something missing?

   To successfully complete this section, you must have a working installation of Node.js and the Windows Azure SDK for Node.js for your platform.

   • Install the Windows Azure SDK for Node.js: Windows installer | Mac installer | Linux download
   • If you are using Mac or Linux, install Node.js from http://nodejs.org. The Windows installer already includes Node.js.

   
   

2. Change directories to the c:\node directory and then enter the following commands to create a new solution named chatapp and a worker role named WorkerRole1:

   PS C:\node> New-AzureServiceProject chatapp
   PS C:\Node> Add-AzureNodeWorkerRole

   You will see the following response:

   

Download the Chat Example

For this project, we will use the chat example from the Socket.IO GitHub repository. Perform the following steps to download the example and add it to the project you previously created.

1. Create a local copy of the repository by using the Clone button. You may also use the ZIP button to download the project.

   

2. Navigate the directory structure of the local repository until you arrive at the examples\chat directory. Copy the contents of this directory to the C:\node\chatapp\WorkerRole1 directory created earlier.

   

   The highlighted items in the screenshot above are the files copied from the examples\chat directory

3. In the C:\node\chatapp\WorkerRole1 directory, delete the server.js file, and then rename the app.js file to server.js. This removes the default server.js file created previously by the Add-AzureNodeWorkerRole cmdlet and replaces it with the application file from the chat example.

Modify Server.js and Install Modules

Before testing the application in the Windows Azure emulator, we must make some minor modifications. Perform the following steps to the server.js file:

1. Open the server.js file in Notepad or other text editor.

2. Find the Module dependencies section at the beginning of server.js and change the line containing sio = require('..//..//lib//socket.io') to sio = require('socket.io') as shown below:

   var express = require('express')
   , stylus = require('stylus')
   , nib = require('nib')
   //, sio = require('..//..//lib//socket.io'); //Original
   , sio = require('socket.io');                //Updated

3. To ensure the application listens on the correct port, open server.js in Notepad or your favorite editor, and then change the following line by replacing 3000 with process.env.port as shown below:

   //app.listen(3000, function () {            //Original
   app.listen(process.env.port, function () {  //Updated
     var addr = app.address();
     console.log('   app listening on http://' + addr.address + ':' + addr.port);
   });

After saving the changes to server.js, use the following steps to install required modules, and then test the application in the Windows Azure emulator:

1. Using Windows Azure PowerShell, change directories to the C:\node\chatapp\WorkerRole1 directory and use the following command to install the modules required by this application:

   PS C:\node\chatapp\WorkerRole1> npm install

   This will install the modules listed in the package.json file. After the command completes, you should see output similar to the following:

   

2. Since this example was originally a part of the Socket.IO GitHub repository, and directly referenced the Socket.IO library by relative path, Socket.IO was not referenced in the package.json file, so we must install it by issuing the following command:

   PS C:\node\chatapp\WorkerRole1> npm install socket.io -save

Test and Deploy

1. Launch the emulator by issuing the following command:

   PS C:\node\chatapp\WorkerRole1> Start-AzureEmulator -Launch

2. When the browser window opens, enter a nickname and then hit enter. This will all you to post messages as a specific nickname. To test multi-user functionality, open additional browser windows using the same URL and enter different nicknames.

   

3. After testing the application, stop the emulator by issuing the following command:

   PS C:\node\chatapp\WorkerRole1> Stop-AzureEmulator

4. To deploy the application to Windows Azure, use the Publish-AzureServiceProject cmdlet. For example:

   PS C:\node\chatapp\WorkerRole1> Publish-AzureServiceProject -ServiceName mychatapp -Location "East US" -Launch

   Note

   Be sure to use a unique name, otherwise the publish process will fail. After the deployment has completed, the browser will open and navigate to the deployed service.

   If you receive an error stating that the provided subscription name doesn't exist in the imported publish profile, you must download and import the publishing profile for your subscription before deploying to Windows Azure. See the Deploying the Application to Windows Azuresection of Build and deploy a Node.js application to a Windows Azure Cloud Service

   

   Note

   If you receive an error stating that the provided subscription name doesn't exist in the imported publish profile, you must download and import the publishing profile for your subscription before deploying to Windows Azure. See the Deploying the Application to Windows Azuresection of Build and deploy a Node.js application to a Windows Azure Cloud Service

Your application is now running on Windows Azure, and can relay chat messages between different clients using Socket.IO.

Next steps

In this tutorial you learned how to create a basic chat application hosted in a Windows Azure Cloud Service. To learn how to host this application in a Windows Azure Web Site, see Build a Node.js Chat Application with Socket.IO on a Windows Azure Web Site.