server.js

var   express = require('express')
    , app = express.createServer()
    , io  = require('socket.io').listen(app)
    , port = process.env.PORT || 3000;

app.listen(port);

app.configure(function() {
    app.use(express.static(__dirname + '/public'));
      app.use(app.router);
});

app.get('/', function (req, res) {
  res.sendfile(__dirname + '/index.html');
});

io.configure(function () {
    io.set('transports', ['xhr-polling']);
    io.set('polling duration', 10);
});

var usernames = {};

var rooms = ['room1', 'room2', 'room3'];

io.sockets.on('connection', function (socket) {

  socket.on('adduser', function(username) {
    socket.username = username;
    usernames[username] = username;
    socket.join('room1');
    socket.emit('updatechat', 'SERVER', 'you have connected to room1');
    socket.broadcast.to('room1').emit('updatechat', 'SERVER', username + ' has connected to this room');
    socket.emit('updaterooms', rooms, 'room1');
  });

  socket.on('sendchat', function (data) {
    io.sockets.in(socket.room).emit('updatechat', socket.username, data);
  });

  socket.on('switchRoom', function(newroom) {
    socket.leave(socket.room);
    socket.join(newroom);
    socket.emit('updatechat', 'SERVER', 'you have connected to ' + newroom);
    socket.broadcast.to(socket.room).emit('updatechat', 'SERVER', socket.username + 'has left this room');
    socket.room = newroom
    socket.broadcast.to(newroom).emit('updatechat', 'SERVER', socket.username + 'has joined this room');
    socket.emit('updaterooms', rooms, newroom);
  });

  socket.on('disconnect', function () {
    delete usernames[socket.username];
    io.sockets.emit('updateusers', usernames);
    socket.broadcast.emit('updatechat', 'SERVER', socket.username + ' has disconnected');
  });
});