Socket.io error hooking into express.js

Question

I'm trying to hook socket.io and express.js together:

var socket = require('./socket_chat/socket.js');

var express = require('express'),
    app = module.exports.app = express();

    var io = require('socket.io').listen(app);

    app.use(express.static(__dirname + '/app'));

io.sockets.on('connection', socket);

At the line: var io = require('socket.io').listen(app); I'm getting an error:

Error: You are trying to attach socket.io to an expressrequest handler function. Please pass a http.Server instance.

There doesn't seem to be anything on SO/google about this error...

Solution 1

You can do it without using http module

app.listen return a server instance you can use for socket.io

const express = require('express');
const app = express();
const server = app.listen(port, () => {
    console.log("Listening on port: " + port);
});
const io = require('socket.io')(server);

Solution 2

You should use http module:

var http = require('http');
var express = require('express'),
    app = module.exports.app = express();

var server = http.createServer(app);
var io = require('socket.io').listen(server);  //pass a http.Server instance
server.listen(80);  //listen on port 80

//now you can use app and io

More details you can find in a documentation: http://socket.io/docs/#using-with-express-3/4

Solution 3

For socket.io to work with express, you need a server instance and therefore attach it to socket.io

I'll use .listen method of express since it returns an http.Server object. Read the docs here

const port = 3000,
      app = require('express')(),
      io = require('socket.io')();

// Your normal express routes go here...

// Launching app
const serverInstance = app.listen(port, () => {
    console.log('App running at http://localhost:' + port);
});

// Initializing socket.io
io.attach(serverInstance);