The chat sample used to illustrate Tomcat's CometProcessor doesn't work. To be fair, it is listed as pseudo code and it's nice in that it illustrates the proper flow, but I wanted more proof and so fleshed out the sample to be able to chat.

The major changes:

• It compiles
• If you request chat, your message is added to the list (original version just throws them away)
• Any request other than chat is a hold. This is the 'long poll' socket -- a response is not returned immediately.
• Chat messages are posted to the held sockets.
• It uses the JSESSIONID cookie to track if there has already been established. If so, it's released. This fixes a case in Internet Explorer where if you navigate away, the socket is still held & when you return to the chat page, you miss message.

The code is here.

Update (2/25/2009): I took down the chat pushlet server, as I'm no longer running Tomcat on port 80. The code (a bit hacky, I know, but I didn't want to completely rewrite the sample) moved around, but it's there again.