Example of how to fallback to alternative websocket library for old protocol clients.

websocket-fallback.js

#!/usr/bin/env node
var WebSocketRequest = require('websocket').request;
var http = require('http');

var server = http.createServer(function(request, response) {
    console.log((new Date()) + " Received request for " + request.url);
    response.writeHead(404);
    response.end();
});
server.listen(8080, function() {
    console.log((new Date()) + " Server is listening on port 8080");
});

var serverConfig =  {
    // All options *except* 'httpServer' are required when bypassing
    // WebSocketServer.
    maxReceivedFrameSize: 0x10000,
    maxReceivedMessageSize: 0x100000,
    fragmentOutgoingMessages: true,
    fragmentationThreshold: 0x4000,
    keepalive: true,
    keepaliveInterval: 20000,
    assembleFragments: true,
    // autoAcceptConnections is not applicable when bypassing WebSocketServer
    // autoAcceptConnections: false,
    disableNagleAlgorithm: true,
    closeTimeout: 5000
};

// Handle the upgrade event ourselves instead of using WebSocketServer
server.on('upgrade', function(req, socket, head) {
    var wsConnection;
    var wsRequest = new WebSocketRequest(socket, req, serverConfig);
    try {
        wsRequest.readHandshake();
        wsConnection = wsRequest.accept(wsRequest.requestedProtocols[0], wsRequest.origin);
        // wsConnection is now live and ready for use
    }
    catch(e) {
        console.log("WebSocket Request unsupported by WebSocket-Node: " + e.toString());
        return;
        // Attempt old websocket library connection here.
        // wsConnection = /* some fallback code here */
    }
    
    handleWebSocketConnect(wsConnection);
});

function handleWebSocketConnect(connection) {
    console.log((new Date()) + " Connection accepted.");
    connection.on('message', function(message) {
        if (message.type === 'utf8') {
            console.log("Received Message: " + message.utf8Data);
            connection.sendUTF(message.utf8Data);
        }
        else if (message.type === 'binary') {
            console.log("Received Binary Message of " + message.binaryData.length + " bytes");
            connection.sendBytes(message.binaryData);
        }
    });
    connection.on('close', function(connection) {
        console.log((new Date()) + " Peer " + connection.remoteAddress + " disconnected.");
    });
}

The library is still under development -- in particular, I'm planning on reworking it to provide a streaming API, and then build a message-oriented API on top of that (in a way that's backward compatible with applications already using the library). That's a fair amount of work, and I'd have to do it multiple times (one for each draft version) to support them all. I'd really rather not complicate the library with extra code that is there to support an obsolete draft version.

As for the AS3WebSocket library - it's an ActionScript 3 library distributed as a .swc file for importing into Flash Builder or use with the open source flex sdk. I haven't written a polyfill shim for javascript-based projects, my AS3WebSocket library is meant to be a client library for flash applications. It probably wouldn't be too hard to write a small flash application to expose the API to JavaScript, but I'm swamped with other work right now :-/

Did anyone succeed in adding node-websocket-server to this example (to get a fallback for draft75/draft76 connections)?

@nicokaiser I haven't had any reports from anyone.. :-/

Unfortunately this does not work, "new WebSocketRequest" rejects older protocols (like draft-76) and closes the socket, so fallback libraries cannot do anything in the "catch" block.

@nicokaiser -- As it turns out, you're quite right! Apologies! I've updated it the code in v0.0.16 not to automatically close the connection. That responsibility is deferred to WebSocketServer in the normal case, or you in the case where you're handling the fallback.

I've updated the gist to reflect my update.

Here is a Gist that implements a working example of a server that handles draft-08/-09/-10 connections with WebSocket-Node and the rest with miksago's node-websocket-server:

https://gist.github.com/1219165