Help with GlassFish 3.1.1 websocket server, onMessage wont invoke

I have managed to get the websocket listener to accept a connection (I see in Wireshark that the server sending a correct response). Both createSocket and onConnect are invoked. However, when I send a message from the client, onMessage wont invoke. I tried to override both onMessage(Websocket, String) and onMessage(Websocket, byte[]) in my WebSocketConnection class that extends WebSocketApplication- no difference in result.

From my HttpServlet, I fire up the websockets with

private final WebSocketConnection wsconn = new WebSocketConnection();

and

WebSocketEngine.getEngine().register(wsconn);

in the init().

Also, the server wont respond to a disconnect from the client.

GlassFish 3.1.1 (build12) with Grizzly-Websockets 1.9.36.

The client I use for testing is http://websocket.org/echo.html

I have enabled websockets in GlassFish.

I'm very thankful for any advice on how to solve this.