http.listen vs app.listen

[nickrttn]

In the index.js the app object is being passed into http.Server(), which is later on called with http.listen(). Is there any difference or upside to this method over just using express' builtin app.listen();? Why and how does this work?

[jsmoorman]

You must pass an HTTP server instance to socket which is created by the line:

var http = require('http').Server(app);

Express' built in listen() function does return an HTTP server instance, so it is possible to use app.listen().

This:

var app = require('express')();
var http = require('http').Server(app); // The server instance is created here.
var io = require('socket.io')(http); // The server instance is passed here.

Is equivalent to:

var app = require('express')();
var server = app.listen(3033); // The server instance is returned from app.listen()
var io = require('socket.io').listen(server); // The server instance is passed here.

However, I'm unsure if either provide any benefits over the other.