server.js

var mongo = require('mongodb').MongoClient,
	client = require('socket.io').listen(8090).sockets;

mongo.connect('mongodb://127.0.0.1/chat',function(err, db){
	if(err) throw err;
	
	client.on('connection',function(socket) {
	
		var col = db.collection('messages'),
		sendStatus = function(s) {
			socket.emit('status',s);
		};
		
		//emit all messages
		col.find().limit(100).sort({_id:1}).toArray(function(err, res) {
				if(err) throw err;
				socket.emit('output', res);
		});
		
		//wait for input
		socket.on('input',function(data){
			var name = data.name,
				message = data.message;
				whitespacePattern = /^\s*$/;
				
			if(whitespacePattern.test(name) || whitespacePattern.test(message))	
			{	
				sendStatus('Name and message is required.');
			}
			else
			{
				col.insert({name:name,message:message}, function(){
				
					//Emit all messages to all clients
					client.emit('output',[data]);
				
					sendStatus({
						message: "message sent",
						clear: true
					});
				});
			}
		});
	});

});