Comet is a programming technique that enables web servers to send data to the client
without having any need for the client to request it. It is a push technique to use
instead of polling to have clients discover new information available at a server.
Clients register with the server as interested in given events or results. They do
this by making a call to the server that is not returned immediately, but only after
something becomes available. It allows creation of event-driven web applications
which are hosted in the browser. You might implement it with signed Applets or Java
Web Start. Other approached to the problem include polling and the server sending out
event notifications to registered listeners (much like Java events). To avoid the
overhead of a sleeping socket connection you might use UDP (User Datagram Protocol).