Jean-François "Grizzly" Arcand has posted two slide decks he used last month during his European tour : • Grizzly (covers basics, use in GlassFish V3, and the recent 1.7 release) • Comet, aka Ajax Push (if you ask Jean-François, it's the best thing since slided bread, and who knows, he may be right :)

Grizzly has been updated to the latest Bayeux Spec. This includes all the distributions including Grizzly 1.0.19, GlassFish v2.1 (9.1ur1 b09), Sailfin and Grizzly snapshots/1.6.2. GlassFish v3 will follow soon. For more details, check out JFA's note.

Comet (also known as "Long Lived HTTP Connections" or "Ajax Push") lets server-side applications notify changes to its clients (Server-Initiated Message Delivery). Typical use-cases include chat, document-sharing application or much more ambitious architectures. Bayeux is a JSON-based protocol specification of Comet and gCometd is the name of the implementation inside Grizzly 1.0.11+ (DOJO or Ajax only) and GlassFish v2 b35+ (JSP, JSF, servlet).

The Comet/Bayeux spec (0.1draft5) released by the Dojo foundation couple of months ago is now supported in GlassFish v2 build 52. Unfortunately, this specification breaks most comet clients. Jean-François "Grizzly" Arcand recommends that you update to the new DOJO library if that's what you're using (and you probably should be since writing a Bayeux client isn't trivial).

More generally on Comet, check out:

• Comet Basics
• A good presentation
• Writing a Comet web application using GlassFish
• This simple, yet very cool demo.