Pushing data to an Applet

Hi,

I have a Java Swing applet in my site. It talks to server via Applet to
Servlet Communication. There is one application running at the server
side, which processes some order.

Now the functionality which I have to build is that the application
should be able to push orders to the applets, so that the users who are
currently watching the applet should be able to see the latest data
automatically without sendinga request.

I searched on web but couldn't find anything as to how can I push data
to all the connected applets of the site.

The solution which I thought is the applet will poll the server after
every say 1 minute to check if there is any new to show. But suppose the
number of user is more and there is nothing new to show, the applets
will unnecessary making the request to the server.

I can't use Socket connection or RMI as the site will browsed outside
the firewall. Is there any way by which I can push data from server to
applets, so that when ever new thing will come server will make
connection with applets and push data thereby using network only when
needed. Unlike in polling the network is used unnecessarily.

Regards
Bhushan