server.js

// SSL Certificates
var fs = require('fs');

var options = {key:  fs.readFileSync('certs/privatekey.pem').toString(),
               cert: fs.readFileSync('certs/certificate.pem').toString(),
               ca:  [fs.readFileSync('certs/certrequest.csr').toString()]}

// Get AppFog port, or set 8080 as default one (dotCloud mandatory)
var port = process.env.VMC_APP_PORT || 8080

// HTTP server
function requestListener(req, res)
{
  res.writeHead(200, {'Content-Type': 'text/html'});
  res.write('This is a DataChannel polyfill backend server. ')
  res.write('You can get a copy of the source code at ')
  res.end('<a href="https://github.com/piranna/DataChannel-polyfill">GitHub</a>')
}

var server = require('http').createServer(requestListener)
//var server = require('https').createServer(options, requestListener)
    server.listen(port);

// DataChannel proxy server
var WebSocketServer = require('ws').Server
var wss = new WebSocketServer({server: server});

//Dict to store connections
wss.sockets = {}

wss.on('connection', function(socket)
{
    // Forward raw message to the other peer
    function onmessage_proxy(message)
    {
        this.peer.send(message.data)
    };

    // Handshake
    socket.onmessage = function(message)
    {
        var args = JSON.parse(message.data)

        var eventName = args[0]
        var socketId  = args[1]

        var soc = wss.sockets[socketId]

        switch(eventName)
        {
            case 'create':  // socketId is the peer ID
                if(soc)
                {
                    // Both peers support native DataChannels
                    if(args[3] && soc.nativeSupport)
                    {
                        // Notify that both peers has native support
                        socket.send(JSON.stringify(['create.native']))
                        soc.send(JSON.stringify(['create.native']))

                        // Close both peers since they have native support
                        socket.close();
                        soc.close();
                    }

                    // At least one of the peers doesn't support DataChannels
                    else
                    {
                        // Register the new peer connection
                        socket.id = id()
                        wss.sockets[socket.id] = socket

                        // Send the other peer the request to connect
                        args[1] = socket.id
                        args.splice(3, 1)

                        soc.send(JSON.stringify(args))
                    }
                }

                // Second peer was not connected
                // Send error message and close socket
                else
                {
                    socket.send(JSON.stringify(['create.error', socketId]))
                    socket.close();
                }

                break

            case 'ready':   // socketId is the UDT ID
                if(soc)
                {
                    // Link peers and update onmessage event to just forward
                    socket.peer = soc
                    soc.peer = socket

                    socket.onmessage = onmessage_proxy
                    soc.onmessage = onmessage_proxy

                    // Send 'ready' signal to the first peer and dettach it
                    soc.send(JSON.stringify(['ready']))

                    delete soc.id
                    delete wss.sockets[socketId]
                }

                // First peer was disconnected
                // Send error message and close socket
                else
                {
                    socket.send(JSON.stringify(['ready.error', socketId]))
                    socket.close();
                }

                break

            // Register peer signaling socket with this ID
            case 'setId':
                wss.sockets[socketId] = socket
                wss.sockets[socketId].nativeSupport = args[2]
        }
    };

    // Peer connection is closed, close the other end
    socket.onclose = function()
    {
        // Sockets were connected, just close them
        if(socket.peer != undefined)
            socket.peer.close();

        // Socket was not connected, remove it from sockets list
        else
            delete wss.sockets[socket.id]
    };
})

// generate a 4 digit hex code randomly
function S4()
{
  return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1)
}

// make a REALLY COMPLICATED AND RANDOM id, kudos to dennis
function id()
{
  return S4()+S4() +"-"+ S4() +"-"+ S4() +"-"+ S4() +"-"+ S4()+S4()+S4()
}