app.js

var favicon = require('static-favicon');
var express= require('express'),
app=express(),
server=require('http').createServer(app),
io=require('socket.io').listen(server),
nicknames=[];

server.listen(3000);

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

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

	socket.on('new user',function(data,callback){
     if(nicknames.indexOf(data)!= -1){
   callback(false);
     } else{
     	callback(true);
     	socket.nickname=data;
     	nicknames.push(socket.nickname);
     	updateNicknames();
     }
	});

	function updateNicknames(){
		io.sockets.emit('usernames',nicknames);
	}
	socket.on('send message', function(data){
        io.sockets.emit('new message',{msg:data,nick:socket.nickname});
	});

	socket.on('disconnect', function(data){
		if(!socket.nickname) return;
        nicknames.splice(nicknames.indexOf(socket.nickname),1);
         updateNicknames();
	})
});