I found the problem: it was me!

The problem is with how I stored multiple sessions.  For example, let's suppose that 3 users have established a websocket.  My code was was storing those 3 sessions in a HashSet.  Then, when I wanted to send each of them a message, I would loop thru the Set of sessions and for each one do a: session.getBasicRemote().sendText(message); .  Trouble is: some of those sessions might have been closed.  So I changed my for-loop to have a try/catch block surrounding each "sendText()" call.

WRONG is:

try {

     for(Session session : sessions) {

          session.getBasicRemote().sendText(message);

     }

}

catch(Exception e) {

}

CORRECT is:

for(Session session : sessions) {

     try {

          session.getBasicRemote().sendText(message);

     }

     catch(Exception e) {

     }

}

Now it works fine.  But now there's another problem: How will I know a websocket has closed so I can remove it from my Set of sessions?  I thought that when the Javascript called "websocketSession.close()" that the server-side "onClose()" method would get called, but it doesn't.  So how will I know?

Thanks.