gistfile1.js

// socket.io 
var socket = io.listen(app); 
var buffer = [];

socket.on('connection', function(client){ 
	client.send({ buffer: buffer });
	client.broadcast({ announcement: client.sessionId + ' connected' });
	
	client.on('message', function(message){
		var msg = { message: [client.sessionId, message] };
		buffer.push(msg);
		if (buffer.length > 15) buffer.shift();
		console.log(msg);
		client.broadcast(msg);
	});

	client.on('disconnect', function(){
		client.broadcast({ announcement: client.sessionId + ' disconnected' });
	});
});