Simple Engineering

WebSocket

The reactive aspect of nodejs applications is synonymous with the nodejs runtime itself. However, the real-time magic is attributed to the WebSocket addition. This article introduces how to integrate WebSocket support within an existing nodejs application.

In this article we will talk about:

  • WebSocket support with or without socket.io
  • WebSocket support with or without expressjs
  • Modularizations of WebSocket

Even though this blog post was designed to offer complementary materials to those who bought my Testing nodejs Applications book, the content can help any software developer to tuneup working environment. You use this link to buy the book. Testing nodejs Applications Book Cover

Show me the code

Express routes use socket.io instance to deliver messages of a socket/socket.io enabled application looks like following:

//module/socket.js - server or express app instance 
module.exports = function(server){
  var io = socket();
  io = io.listen(server);
  io.on('connect', fn); 
  io.on('disconnect',fn);
};
//OR
//module/socket.js 
var io = require('socket.io');
module.exports = function(server){
  //server will be provided by the calling application
  //server = require('http').createServer(app);
  io = io.listen(server);
  return io;
};

//module/routes.js - has all routes initializations
var route = require('express').Router();
module.exports = function(){
    route.all('',function(req, res, next){ 
    	res.send(); 
    	next();
 });
};

//in server.js 
var app = require('express').express(),
  server = require('http').createServer(app),
  sio = require('module/socket.js')(server);

//@link http://stackoverflow.com/a/25618636/132610
//Sharing session data between SocketIO and Express 
sio.use(function(socket, next) {
    sessionMiddleware(socket.request, socket.request.res, next);
});

//application app.js|server.js initialization, etc. 
require('module/routes')(server); ;

What can possibly go wrong?

When working in this kind of environment, we will find these two points to be of interest, if not challenging:

  • For socket.io application to use same expressjs server instance, or sharing route instance with socket.io server
  • Sharing session between socket.io and expressjs application

Conclusion

In this article, we revisited how to add real-time experience to a nodejs application. The use of WebSocket and Pub/Sub powered by a key/value data store was especially the main focus of this article. There are additional complimentary materials in the “Testing nodejs applications” book.

References

#snippets #nodejs #integration #WebSocket