Comet: Low Latency Data for the Browser: I think the end of the request-response model of HTTP communications is upon us. This reverses Ajax — using Comet (still not quite sure how it’s done), the server can reach out and contact the browser at will.
Comet applications can deliver data to the client at any time, not only in response to user input. The data is delivered over a single, previously-opened connection. This approach reduces the latency for data delivery significantly.