simple TCP socket chat server doesn't work on heroku

I wanted to build a node.js chat server on heroku, the chat clients are going to be iOS apps.

My first attempt is to build a server based on socket.io. It works, but I don't like the fact the the iOS app is talking to the server using long polling instead of websocket or tcp socket.

So my second attempt is to build the server using real TCP socket, code as below:

var net = require('net');

var sockets = [];

var server = net.createServer(function(socket){
    sockets.push(socket);
    socket.on('data', function (data) {
        for(var i=0; i< sockets.length; i++)
        {
            sockets[i].write(data);
        }
    });
    socket.on('end', function() {
        var i  = sockets.indexOf(socket);
        sockets.splice(i, 1);
    })
});

var port  = process.env.PORT || 5000;
console.log("server listening to port " + port);
server.listen(port);

If I deploy this node.js server code in localhost, i can successfully send and receives chat to the TCP server using Terminal as test client

nc localhost 5000

BUT, if I deploy this server code in heroku, I couldn't establish a tcp connection with the server anymore.

My understanding is server will be listening at the process.env.PORT.

So I first traced out this port that the server is listening, e.g. 30134.

Then If I attempt to connect in this way:

nc http://my-heroku-app.herokuapp.com 30134

Nothing happens.

I think I have some fundamental misunderstanding somewhere. Can anyone guide me? Is Real TCP socket chat possible on heroku server?