HTML5 Event Source API not working through reverse proxy (IIS7.5)

On a website hosted on IIS 7.5 i make several HTTP Calls to a node.js server running on localhost:3000. So the reverse proxy fordwards from http://example.com/node/* --> localhost:3000/*

Every HTTP call works perfectly except one:

A HTTP Call that uses HTML5 Event Source API (Server-sent events) to sent a message to the client. Do I need to perform additional customizations to allow this type of calls via the IIS reverse proxy?

client:

var source = new EventSource("http://example.com/node/payments?wallet="+btcwalletdir);
                      source.addEventListener('message', function(e) { 
                             // do whatever here with e
                         }  
}, false);

node.js:

app.get('/payments', function(req, res) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "X-Requested-With");
    res.connection.setTimeout(0); // this could take a while

    res.writeHead(200, {
        'Content-Type': 'text/event-stream',
        'Connection': 'keep-alive',
        'Cache-Control': 'no-cache',
    });
    ee.on("payment"+req.query.wallet, function (datoak) {
            res.write("data: "+ JSON.stringify({'wallet': datoak.address, 'refund_address': datoak.refund_address,'payment_status': 'paid'})+ "\n\n")
            });
});

Regards,