chat.js

var express = require('express'),
 app = express(),
 http = require('http'),
 server = http.createServer(app),
 io = require('socket.io').listen(server);

server.listen(3000);

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

var usernames = {};
var rooms = ['room1', 'room2', 'room3'];


io.sockets.on('connection', function(socket) {
 //Everything we do in here is related to socket connections
 //socket is the user, we can communicate with it from here.
 socket.on('addUser', function(username){
 //When the client emits an add user, we perform that functionality
 socket.username = username;
 console.log(username + "Connected");

 //tell the user to join the default room
 socket.room = rooms[0];
 //save the user
 usernames[username] = username;
 //physically join the player and it's socket to the room
 socket.join(socket.room);

 //emit, to the client, you've connected
 updateClient(socket, username, socket.room);

 //emit to the room, a person has connected
 //socket.broadcast.to(socket.room).emit('updateChat', 'SERVER', username + ' has connected');
 updateChatRoom(socket, 'connected');
 updateRoomList(socket, socket.room);

 });
 //take in the message, emit it
 socket.on('sendChat', function (data) {
 //send the message to everyone
 console.log(socket.username + " sent a message");
 io.sockets.in(socket.room).emit('updateChat', socket.username, data);
 })
 //when we switch a room
 socket.on('switchRoom', function(newRoom) {
 socket.leave(socket.room);
 socket.join(newRoom);
 //update client
 updateClient(socket, socket.username, newRoom);
 //update old room
 updateChatRoom(socket, 'disconnected');
 //change room
 socket.room = newRoom;
 //update new room
 updateChatRoom(socket, 'connected');
 updateRoomList(socket, socket.room);
 })
 //disconnecting from a room
 socket.on('diconnect', function() {
 // remove the user from global list
 delete usernames[socket.username];
 // tell the user list on the client side
 io.sockets.emit('updateUsers', usernames);
 //tell everyone\
 updateGlobal(socket, 'disonnected');
 //leave channel
 socket.leave(socket.room);
 })


});
//update single client with this.
function updateClient(socket, username, newRoom) {
 socket.emit('updateChat', 'SERVER', 'You\'ve connected to '+ newRoom);
}

function updateRoomList(socket, currentRoom ) {
 socket.emit('updateRooms', rooms, currentRoom);
}

//We will use this function to update the chatroom when a user joins or leaves
function updateChatRoom(socket, message) {
 socket.broadcast.to(socket.room).emit('updateChat', 'SERVER', socket.username + ' has ' + message);
}
//We will use this function to update everyone!
function updateGlobal(socket, message) {
 socket.broadcast.emit('updateChat', 'SERVER', socket.username + ' has ' + message);
}