app.js

// Dependency
var express  = require('express');
var mongoose = require('mongoose');
var bodyParser = require('body-parser');
var app      = express();
var server   = require('http').Server(app);
var io       = require('socket.io')(server);

// Config
app.use(bodyParser.urlencoded({ extended: true }));
app.use(function(req,res,next){
	req.io = io;
	next();
});

// Tell express where to serve static files from
app.use(express.static(__dirname + '/public'));

// Connect to DB
mongoose.connect("mongodb://127.0.0.1:27017/realtime_chart");

var schema = mongoose.Schema({name: String});
var Vote = mongoose.model('Vote', schema);

/* 
Routes
*/

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

// Route for voting
app.post('/vote', function(req, res) {
	var field = [{name: req.body.name}];

	var newVote = new Vote(field[0]);
	
	newVote.save(function(err, data) {
		console.log('Saved');
	});

	Vote.aggregate(
		
		[{ "$group": {
			"_id": "$name",
			"total_vote": { "$sum": 1 }
		}}],

		function(err, results) {
			if (err) throw err;
			console.log(results);
			req.io.sockets.emit('vote', results);
		}
		);

	res.send({'message': 'Successfully added.'});
});

app.get('/data', function(req, res) {
	Vote.find().exec(function(err, msgs) {
		res.json(msgs);
	});
});

/*
Socket.io Setting
*/

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

	Vote.aggregate(

		[{ "$group": {
			"_id": "$name",
			"total_vote": { "$sum": 1 }
		}}],

		function(err, results) {
			if (err) throw err;

			socket.emit('vote', results);
		}
	);
});

// Start
server.listen(3000);
console.log('Open http://localhost:3000');