CODEWITHSUNDEEP
node.jstcpwebsocket
bodokaiser
bodokaiser

Reputation: 15752

Why do nodejs WebSocket implementations not use net.Server?

I am currently experiencing with Websockets.

By reviewing some active projects/implementations like einaros/ws (and others as well) I found out that they implement the server their own. Instead of using the node net module which provides a tcp server. Is there a reason for this approach?

https://github.com/einaros/ws/blob/master/lib/WebSocketServer.js

Regards

Update:

var server = net.createServer(function(c) {

  c.on('data', function(data) {
    // data is a websocket fragment which has to get parsed
  });
  // transformToSingleUtfFragment is building a websocket valid
  // byte fragment which contains hello as application payload
  // and sets the right flags so the receiver knows we have a single text fragment
  c.write(transformToSingleUtfFragment('hello'));
  c.pipe(c);
});
server.listen(8124, function() { //'listening' listener
  console.log('server bound');
});

Upvotes: 3

Views: 2189

Answers (1)

Ivo Wetzel
Ivo Wetzel

Reputation: 46756

WebSocket's a a protocol layered on top of normal HTTP.

How it works is basically that the browser sends a UPGRADE HTTP request and then makes use of the HTTP 1.1 keep alive functionality to keep the underlying TCP socket of the HTTP connection open.

The data is then send via the WebSocket Protocol (Rather large RFC behind the link), which itself is built on top of TCP.

Since the HTTP part is required, and you need to re-use the TCP connection from that one, it makes sense to go with the normal HTTP server instead of net.Server. Otherwise you'd had to implement the HTTP handling part yourself.

Implementing the WebSocket Protocol needs to be done in either case, and since any HTTP connection can be upgraded, you can, in theory, simply connect your WebSocket "server" to the normal HTTP Server on Port 80 and thus handle both normal HTTP requests and WebSockets on the same port.

Upvotes: 7

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