Instant Responses

On twitter when someone we 开发者_StackOverflow中文版follow tweet something, its shown our timeline instantly. Twitter i followed the request and response with firebug there is no preiodical timer to sent a request than receive response (in this case tweets) its look like instantly receiving the new tweets. What is the methodology to do that. And what is the name of that. Can you give me some book or internet sites advices to read?

Summary: How can show the new data as soon as it arrived and how to implement that?Language does not matter.

Open an HTTP request with AJAX, but keep the connection with the server open, such that the server can continually send updated data to the browser without the overhead time and data transfer of closing and opening a new connection.