PUB/SUB with java applet subscriber

For a banking application (trading) we think about a natural@web configuration on unix. When a product a partly bought we need to be able to inform plenty of users that this has been done. So the central server has to publish a message to all several users on the browser. We think about an applet which subscribes (for all end users interested). We need to implement what is called strealing in this sector. Ideas are wellcome.