Then if you are getting a message of type RESPONSE with a blank/empty error then the problem must be in your code somewhere else. Either it’s stalling or unable to process the incoming messages correctly.
My own pubsub handler is working as expected. The only difference we have is that you are using code that matches W3C WebSocket API and I am not.
You have
$socket.onmessage = socketMessage;
Where I have instead
ws.on(‘message’, function(msg) { // do stuff with msg });
I’ve not tried using the W3C method with the Twitch PubSub to confirm if that works.