Create WebSockets between a TCP server and HTTP server in node.js

Question

I have created a TCP server using Node.js which listens to clients connections. I need to transmit data from TCP server to HTTP server again in Node.js possibly through a Websocket (socket.io).

However, I do not know how to create such connection such that TCP server is able to push data to HTTP server through Websocket.

Many Thanks.

Sherlocke

You can use socket.io-client to connect HTTP server using socket.io – Myrmecophagous

@Myrmecophagous : Can you please help me with the code sample please ? – Sherlocke

Take the code from socket.io example socket.io/#how-to-use for client-side, only JavaScript part and var io = require('socket.io-client'); – Myrmecophagous

Answer 1

I was trying lot of things to get this work. Most of the time I was relying on socket.io to get this working, but it was just not working with TCP.

However, net.Socket suffices the purpose.

Here is the working example of it.

TCP Server

var net = require('net');

var HOST = 'localhost';
var PORT = 4040;

var server = net.createServer();
server.listen(PORT, HOST);

server.on('connection', function(sock) {
    console.log('CONNECTED: ' + sock.remoteAddress +':'+ sock.remotePort);
sock.write("TCP sending message : 1");
    console.log('Server listening on ' + server.address().address +':'+ 
        server.address().port);
}).listen(PORT, HOST);

HTTP Server

var http = require('http').createServer(httpHandler),
    fs = require("fs"),
    wsock = require('socket.io').listen(http),
    tcpsock = require('net');

var http_port = 8888;

var tcp_HOST = 'localhost';
var tcp_PORT = 4040;

/**
 * http server
 */
function httpHandler (req, res) {
  fs.readFile(__dirname + '/index.html',
  function (err, data) {
    if (err) {
      res.writeHead(500);
      return res.end('Error loading index.html');
    }

    res.writeHead(200);
    res.end(data);
  });
}

http.listen(http_port);
console.info("HTTP server listening on " + http_port);

wsock.sockets.on('connection', function (socket) { 

    var tcpClient = new tcpsock.Socket();
    tcpClient.setEncoding("ascii");
    tcpClient.setKeepAlive(true);

    tcpClient.connect(tcp_PORT, tcp_HOST, function() {
        console.info('CONNECTED TO : ' + tcp_HOST + ':' + tcp_PORT);

        tcpClient.on('data', function(data) {
            console.log('DATA: ' + data);
            socket.emit("httpServer", data);
        });

        tcpClient.on('end', function(data) {
            console.log('END DATA : ' + data);
        });
    });

    socket.on('tcp-manager', function(message) {
        console.log('"tcp" : ' + message);
        return;
    });

    socket.emit("httpServer", "Initial Data");
});

Browser Client

<script src="/socket.io/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost');
  socket.on('httpServer', function (data) {
    console.log(data);
    document.write(data + "\r\n");
    socket.emit('tcp', "For TCP");
  });
</script>

This way, there is a socket opened between HTTP server and TCP server in Node.js.

Sherlocke

So 2 different servers? – Charming

@Ravis to send message from web client i tried to post a message to http server which end with Allow-origin-allow-origin error. Is it a correct way to post message from web client or i am doing any mistake? i have raised a question stackoverflow.com/q/32999794/4657065 . thanks for your help. – Radii

Answer 2

If you need to communicate server-server than websockets is probably not a best choice. Try one of RPC libraries, or just use HTTP or your own protocol.

Wolfy

Hey, Thanks @Andrey and rdrey. Although I got the sockets working between a TCP and HTTP Server in Node.js. However, I would definitely try the RPC libraries in this case. Thanks a lot. :) – Sherlocke

Answer 3

You can use either socket.io or ws (only WebSocket) on Node.js as client (not only in browser)

var io = require('socket.io-client');
var socket = io.connect('http://IP address of Websocket server');
socket.on('news', function (data) {
  console.log(data);
  socket.emit('my other event', { my: 'data' });
});

Myrmecophagous

I tried this. However, the problem is that it is not able to communicate with the TCP server created on Node.js. i.e. var app = require('net').createServer(handle); But it works when I change it to http. – Sherlocke