CometD is the highly scalable, clustered, web messaging library that supports publish-subscribe, peer-to-peer, and remote-call modes of operation, available in Java and JavaScript (browser and Node) platforms.
With CometD, requests can be batched, connections can be shared, you can avoid tripping on browser connection limits, and you can enforce better organization and security through channels and filters. CometD can also be used to communicate to a variety of user interface frameworks, such as Dojo or GWT.
CometDs exceptional scalability is tested every day by massive online games, call centers, freight tracking systems, and more with minimal resource usage.