Now, let's look at how to build a simple Ajax chat system using Ajax with the long polling technique. We've used the jQuery framework of JavaScript for most of the JavaScript code. In the traditional Ajax polling system, a request is sent to the server at regular intervals; so, whether there is new data or not, the server has to deal with the HTTP request. But in Ajax, with the long polling technique, the request is kept open from the server-side script until the server has new data to send to the browser.

However, in our chat example, we're keeping the Ajax request open for 90 seconds. If there is no new chat message received from the server, the connection is closed and a new Ajax polling is opened.

Getting ready

First of all, let's look at what the interface of this application is like:

This chat utility has a very simple interface. You need to set a username to send chat messages.