Is it possible to enable tcp, http and websocket all using the same port?

Question

I am trying to enable tcp, http and websocket.io communication on the same port. I started out with the tcp server (part above //// line), it worked. Then I ran the echo server example found on websocket.io (part below //// line), it also worked. But when I try to merge them together, tcp doesn't work anymore.

SO, is it possible to enable tcp, http and websockets all using the same port? Or do I have to listen on another port for tcp connections?

var net = require('net');
var http = require('http');
var wsio = require('websocket.io');

var conn = [];

var server = net.createServer(function(client) {//'connection' listener
    var info = {
        remote : client.remoteAddress + ':' + client.remotePort
    };
    var i = conn.push(info) - 1;
    console.log('[conn] ' + conn[i].remote);

    client.on('end', function() {
        console.log('[disc] ' + conn[i].remote);
    });

    client.on('data', function(msg) {
        console.log('[data] ' + conn[i].remote + ' ' + msg.toString());
    });

    client.write('hello\r\n');
});

server.listen(8080);

///////////////////////////////////////////////////////////

var hs = http.createServer(function(req, res) {
    res.writeHead(200, {
        'Content-Type' : 'text/html'
    });
    res.end(['<script>', "var ws = new WebSocket('ws://127.0.0.1:8080');", 'ws.onmessage = function (data) { ws.send(data); };', '</script>'].join(''));
});

hs.listen(server);

var ws = wsio.attach(hs);
var i = 0, last;

ws.on('connection', function(client) {

    var id = ++i, last

    console.log('Client %d connected', id);

    function ping() {
        client.send('ping!');
        if (last)
            console.log('Latency for client %d: %d ', id, Date.now() - last);
        last = Date.now();
    };

    ping();
    client.on('message', ping);

});

Solution

You can have multiple different protocols handled by the same port but there are some caveats:

• There must be some way for the server to detect (or negotiate) the protocol that the client wishes to speak. You can think of separate ports as the normal way of detecting the protocol the client wishes to speak.

• Only one server process can be actually listening on the port. This server might only serve the purpose of detecting the type of protocol and then forwarding to multiple other servers, but each port is owned by a single server process.

• You can't support multiple protocols where the server speaks first (because there is no way to detect the protocol of the client). You can support a single server-first protocol with multiple client-first protocols (by adding a short delay after accept to see if the client will send data), but that's a bit wonky.

An explicit design goal of the WebSocket protocol was to allow WebSocket and HTTP protocols to share the same server port. The initial WebSocket handshake is an HTTP compatible upgrade request.

The websockify server/bridge is an example of a server that can speak 5 different protocols on the same port: HTTP, HTTPS (encrypted HTTP), WS (WebSockets), WSS (encrypted WebSockets), and Flash policy response. The server peeks at the first character of the incoming request to determine if it is TLS encrypted (HTTPS, or WSS) or whether it begins with "<" (Flash policy request). If it is a Flash policy request, then it reads the request, responds and closes the connection. Otherwise, it reads the HTTP handshake (either encrypted or not) and the Connection and Upgrade headers determine whether it is a WebSocket request or a plain HTTP request.

Disclaimer: I made websockify

Comments

[Dax Joshi]

@kanaka : how many clients can connect to a single port ? I want to know that at a time how many web socket connections a Java web app can handle ? On each web socket request from client do we need a diff port on server ?

[kanaka]

@DaxJoshi that's probable better as a separate question. It also really doesn't have to do anything with Websockets. The server port where TCP connections are accepted can handle a lot of connections. You don't a separate server port for each client. In the websockify case, if you are want different clients to connect to different targets via websockify, then you should look at the TokenFile plugin/target config functionality of websockify.

[curiouser]

No, you cannot have multiple "servers" or services bound to the same port, but you can certainly have a single service that can handle both HTTP and Websocket requests.