What is the Apache Tomcat Comet API
The term Comet was coined by Alex at the Dojo Foundation, it might be a good start to read the introduction on the Comet "http://alex.dojotoolkit.org/?p=545"
Tomcat has a Comet implementation, this page is intended to serve as a quick FAQ to explain the basic question around Comet.
What Is Comet?
Comet is a client/server interaction handled over one HTTP request and one HTTP response
Comet is able to push data from the server and from the client, to over come the regular HTTP request polling scalability limitation
Comet is a way to do asynchronous servlets in Tomcat, ie send a response asynchronously to a client
Comet is implemented using the Comet Processor/Comet Event interfaces in Tomcat
Comet is an event based implementation, events are mainly thrown based on underlying IO
A presentation on Tomcat Comet can be found here "http://people.apache.org/~fhanik/ApacheCon2007-ZeroLatencyHTTP.ppt"
What Comet is Not.
It is not a socket API.
It is not a high level poller, for underlying poll()/select() methods
It is not
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