socket.io + mongodb source code

app.js

//
/**
 * Module dependencies.
 * https://blogs.msdn.microsoft.com/cdndevs/2014/09/19/a-chatroom-for-all-part-3-building-a-backend-with-node-mongo-and-socket-io/
 */

var express = require('express');
var routes = require('./routes');
var user = require('./routes/user');
var http = require('http');
var path = require('path');

var mongo = require('mongodb').MongoClient;

var app = express();

// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(require('stylus').middleware(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'public')));

// development only
if ('development' == app.get('env')) {
  app.use(express.errorHandler());
}

app.get('/', routes.index);
app.get('/users', user.list);

var serve = http.createServer(app);
var io = require('socket.io')(serve);

serve.listen(app.get('port'), function () {
    console.log('Express server listening on port ' + app.get('port'));
});

io.on('connection', function (socket) {
    console.log('a user connected');

    mongo.connect(process.env.CUSTOMCONNSTR_MONGOLAB_URI, function (err, db) {
        var collection = db.collection('chat messages')
        var stream = collection.find().sort({ _id : -1 }).limit(10).stream();
        stream.on('data', function (chat) { socket.emit('chat', chat); });
    });

    socket.on('disconnect', function () {
        console.log('user disconnected');
    });

    socket.on('chat', function (msg) {
        mongo.connect(process.env.CUSTOMCONNSTR_MONGOLAB_URI, function (err, db) {
            var collection = db.collection('chat messages');
            collection.insert({ content: msg }, function (err, o) {
                if (err) { console.warn(err.message); }
                else { console.log("chat message inserted into db: " + msg); }
            });
        });

        socket.broadcast.emit('chat', msg);
    });
});