//app.js
var express = require('express');
var app = express();
var serv = require('http').Server(app);

app.get('/',function(req, res) {
	res.sendFile(__dirname + '/client/index.html');
});
app.use('/client',express.static(__dirname + '/client'));

serv.listen(2000);
console.log("Server started.");

var SOCKET_LIST = {};

var io = require('socket.io')(serv,{});
io.sockets.on('connection', function(socket){
	socket.id = Math.random();
	socket.x = 0;
	socket.y = 0;
	socket.number = "" + Math.floor(10 * Math.random());
	SOCKET_LIST[socket.id] = socket;

	socket.on('disconnect',function(){
		delete SOCKET_LIST[socket.id];
	});

});

setInterval(function(){
	var pack = [];
	for(var i in SOCKET_LIST){
		var socket = SOCKET_LIST[i];
		socket.x++;
		socket.y++;
		pack.push({
			x:socket.x,
			y:socket.y,
			number:socket.number
		});
	}
	for(var i in SOCKET_LIST){
		var socket = SOCKET_LIST[i];
		socket.emit('newPositions',pack);
	}




},1000/25);


//index.html
<canvas id="ctx" width="500" height="500" style="border:1px solid #000000;"></canvas>

<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script>
<script>
	var ctx = document.getElementById("ctx").getContext("2d");
	ctx.font = '30px Arial';

	var socket = io();

	socket.on('newPositions',function(data){
		ctx.clearRect(0,0,500,500);
		for(var i = 0 ; i < data.length; i++)
			ctx.fillText(data[i].number,data[i].x,data[i].y);
	});
</script>