NodeJS and Socket.io

Question

I have just installed these nodejs and socket.io but I am having problems with getting the client to connect to the server.

In my server I have:

var http = require('http');
http.createServer(function (req, res) {
 res.writeHead(200, {'Content-Type': 'text/plain'});
 res.end('Hello World\n');
}).listen(3000, 'localhost');
console.log('Server running at http://localhost:3000/');
var io = require('socket.io').listen(3000);
io.sockets.on('connection', function (socket) {
 socket.emit('Hi.') ;
});

And on my client:

<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io.connect('http://localhost:3000');
socket.on('connect', function () {
 socket.emit('set nickname', confirm('What is your nickname?'));
 socket.on('ready', function () {
 console.log('Connected !');
 socket.emit('msg', confirm('What is your message?'));
 });
});

I am getting a number of errors in Chrome inspector:

GET http://localhost:9261/socket.io/socket.io.js 404 (Not Found)
Uncaught ReferenceError: io is not defined

Answer 1

you are not serving the client via nodeJS, this will not work :

<script src="/socket.io/socket.io.js"></script>

try using the this instead:

<script src="http://localhost:3000/socket.io/socket.io.js"></script>

• imperium2335: I have tried that, I don't get the 404 anymore, just get require and io not defined.
• Saad Bourziza: are you sure you have installed socket.io ? you must open a terminal, go to the same directory as your server and then write 'npm install socket.io'
• imperium2335: im using windows, I used command prompt to install it in my current app folder (im using dreamweaver), it installed socket.io into a folder called node_modules, so the directory is like this: F:\xampp\htdocs\mySite\node_modules\socket.io

Answer 2

It seems like you're sending only the 'Hello World' to the client, not the html with the client code.

Your server code should look like this (from http://socket.io/#how-to-use ):

var app = require('http').createServer(handler)
 , io = require('socket.io').listen(app)
 , fs = require('fs')
app.listen(80);
function handler (req, res) {
 fs.readFile(__dirname + '/index.html',
 function (err, data) {
 if (err) {
 res.writeHead(500);
 return res.end('Error loading index.html');
 }
 res.writeHead(200);
 res.end(data);
 });
}
io.sockets.on('connection', function (socket) {
 socket.emit('news', { hello: 'world' });
 socket.on('my other event', function (data) {
 console.log(data);
 });
});

Your client code should be in index.html. Also make sure that you have a folder named socket.io that contains the script socket.io.js

• imperium2335: I have gone through it a couple of times but I still can't seem to get it working. I now have the errors: Uncaught ReferenceError: require is not defined Uncaught ReferenceError: io is not defined
• mihai: "require is not defined" - seems like you're using require on the client side (which is wrong). How are you running the server?
• imperium2335: From command prompt using the command: node server.js, it runs fine with no errors.
• imperium2335: By the way I'm running the server on the same machine as I am trying to run the client, is this not possible? Must be on a different machine/VM?
• imperium2335: The code above is now giving me an error when I try to run the server: Cannot find module 'socket.io'

Answer 3

It is not able to connect because your client is not able to find socket.io.js you can resolve by using proper file, from node_modules\socket.io\node_modules\socket.io-client\dist directory use socket.io.js and put it into your local directory and use it in script tag.

Answer 4

<script src="http://localhost:3000/socket.io/socket.io.js"></script>var socket = io.connect("http://localhost:3000");

for this way client connected to node server.This will work

Answer 5

Also note that when you move to production the code in your client should be updated:

var socket = io.connect('http://localhost:3000');

To something like

var socket = io.connect('my_host');

I've sent the my_host to the client side script with the page where I'm loading socket.io, by extracting the parameters req.headers.host, so for me it looks like:

 io.connect('http://' + host)

You can expose variables on the client side through express-expose.

Answer 6

This is likely because io was not properly instantiated, thus Uncaught ReferenceError: io is not defined

// Instantiate without argument
var io = require('socket.io')();
// Instantiate with new keyword
var Server = require('socket.io')
 , io = new Server();
// Instantiate io server with app as argument
var app = require('http').createServer(handlerFunc)
 , io = require('socket.io')(app);
app.listen(80);
// Attaching socket.io with express server
var app = express()
 , server = require('http').createServer(app)
 , io = require('socket.io')(server);
server.listen(80, handlerFunc);