That's just it: the web server will only send stuff to the browser in response to a request from the browser. So how's the browser to know when to make a request?
You could use regular (and irritatingly frequent) browser refreshes (ick!), but in the long run I think a better solution would be to see if there's some telnet-in-Java applet (funnily enough, a Google search on "telnet in Java applet" works quite well) that could be used instead. That's assuming that using a telnet client instead of a web browser is out of the question 🙂