如何创建实时AJAX？

Question

A good example of what I want is a chat system, where I send a message to someone and he can instantly see my message and vice versa.

So I want the best way to track if in the database there is a new answer for me if yes then show it with AJAX.

Example Websites:

1. Twitter
2. Friend Feed

Answer 1

You probably want to look at Comet, or one of the other push technologies