Twitter is a service that allows users to publish and subscribe to real-time messaging updates from friends. Twitter's architecture is based on a 'push' model just like the Comet technique, where users are automatically notified instead of needing to constantly poll for updates. Jean-Francois Arcand illustrates how to use the Grizzly Comet implementation and create a similar twitter like application in 150 lines of Java code. Read Jean-Francois's post 'Writing a Twitter like application using Grizzly Comet part 1: The Servlet'