README.md

OpenTok Hello World Node

This is a simple demo app that shows how you can use the OpenTok Node SDK to create Sessions, generate Tokens with those Sessions, and then pass these values to a JavaScript client that can connect and conduct a group chat.

Running the App

First, download the dependencies using npm in this directory.

$ npm install

Next, add your own API Key and API Secret to the environment variables. There are a few ways to do this but the simplest would be to do it right in your shell.

$ export API_KEY=0000000
$ export API_SECRET=abcdef1234567890abcdef01234567890abcdef

Finally, start the app using node

$ node index.js

Visit http://localhost:3000 in your browser. Open it again in a second window. Smile! You've just set up a group chat.

Walkthrough

This demo application uses the express web framework. It is a popular web framework and similar to others. Its concepts won't be explained but can be explored further at the website linked above.

Server module (index.js)

The first thing done in this file is to require the the dependencies. We now have the express framework, and most importantly the OpenTok SDK available.

// Dependencies
var express = require('express'),
    OpenTok = require('../../lib/opentok');

Next the app performs some basic checks on the environment and initializes the express application (app).

The first thing that we do with OpenTok is to initialize an instance. The very next thing we do is create a Session. This application will be setting up a group chat, where anyone that loads the page will be be connected to the same Session. So before we get started we need one sessionId, and that will be used for every client that connects. In many applications, you would store this value in a database. Once the Session is created and there are no errors, we store that sessionId in our app. Then we call an init function when we know that the app is ready to start.

// Initialize OpenTok and store it in the express app
var opentok = new OpenTok(apiKey, apiSecret);

// Create a session and store it in the express app
opentok.createSession(function(err, session) {
  if (err) throw err;
  app.set('sessionId', session.sessionId);
  // We will wait on starting the app until this is done
  init();
});

Now we are ready to configure some routes. We only need one GET route for the root path because this application only has one page. Inside the route handler, we just need to get the three values a client will need to connect: sessionId, apiKey, and token. The sessionId is stored in the express app, so we get it from there. The apiKey is available from the outer scope. Last, we generate a fresh token for this client so that it has permission to connect.

app.get('/', function(req, res) {
  var sessionId = app.get('sessionId'),
      // generate a fresh token for this client
      token = opentok.generateToken(sessionId);

  // ...
  });
});

To finish the response we load a template called index.ejs in the views/ directory, and pass in the three values.

  res.render('index.ejs', {
    apiKey: apiKey,
    sessionId: sessionId,
    token: token
  });

Finally, we have the init function that we called from inside the createSession callback. To start the express app, it calls the listen method, and log that the app is ready.

// Start the express app
function init() {
  app.listen(3000, function() {
    console.log('You\'re app is now ready at http://localhost:3000/');
  });
}

Main Template (views/index.ejs)

This file simply sets up the HTML page for the client JavaScript application to run, imports the JavaScript library, and passes the values created by the server into the client application public/js/helloworld.js.

JavaScript Applicaton (public/js/helloworld.js)

The group chat is mostly implemented in this file. At a high level, we connect to the given Session, publish a stream from our webcam, and listen for new streams from other clients to subscribe to.

For more details, read the comments in the file or go to the JavaScript Client Library for a full reference.