NodeJS and Socket.io

Question

NodeJS and Socket.io

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

node.js
socket.io

Answer 1

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

Answer 2

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>

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

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 5

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);

Answer 6

<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