How one can know if the client has closed the connection

I've been playing with the new Servlet 3.0 async features with Tomcat 7.0.4. I found this Chat Application, that lets clients hang on GET request to get message updates. This is working just fine when it comes to receiving the mess开发者_Go百科ages.

The problem arises when the client is disconnected i.e. the user closes the browser. It seems that the server does not raise IOException, even though the client has disconnected. The message thread (see the source code from link above) is happily writing to all stored AsyncContext's output streams.

Is this a Tomcat bug? or am I missing something here? If this is not a bug, then how I'm supposed to detect whether the client has closed the connection?

The code there at line 44 - 47 is taking care of it,

} catch(IOException ex) {
    System.out.println(ex);
    queue.remove(ac);
}

And here too at 75 - 83, using timeout thingie,

req.addAsyncListener(new AsyncListener() {
    public void onComplete(AsyncEvent event) throws IOException {
        queue.remove(ac);
    }

    public void onTimeout(AsyncEvent event) throws IOException {
        queue.remove(ac);
    }
});

EDIT: After getting a little more insight.

1. Tomcat 7.0.4 is still in beta. So, you can expect such behaviour
2. I tried hard but can't find the method setAsyncTimeout() in the doc, neither here, nor here. So, I think they dropped it completely in the final version due to some unknown valid reason
3. The example states, "why should I use the framework instead of waiting for Servlet 3.0 Async API". Which infers that its written before the final thingie

So, what I can say, after combining all these fact, that you are trying to work with the thing that is broken in a sense. That also, may be, the reason for different and weird results.