engine.io.middleware.js

var app = require('express')(),
    server = require('http').Server(app),
    io = require('engine.io').attach(server);

// Use this middleware to workaround "Access-Control-Allow-Origin" errors on the client.
app.use(function (req, res, next) {
        res.setHeader('Access-Control-Allow-Origin', "http://theWebsiteThatOpensSocketConnection.com");
        res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
        res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
        res.setHeader('Access-Control-Allow-Credentials', 'true');

        next();
    }
);

// Proxied by NGINX. See below.
server.listen(3045);

// Don't forget to set up NGINX properly to allow HTTP upgrades,
// Otherwise engine.io will ALWAYS use long polling, which is not efficient.
//
// NGINX Configuration:
/*
    server {
        listen 80;
        server_name pipe.awesomewebsocketserver.com;
        
        location / {
            proxy_pass   http://127.0.0.1:3045;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_set_header Host $host;
        }
    }
*/