Session time out not working properly

In my web application I have set the session timeout for 30 minutes. But users has complai开发者_C百科ned me that the application session doesn't time out properly. In clint side once a 30 seconds it sends ajax requst to the webserver to retrieve data from the server. Is this automated ajax request avoid the session being time out. Can some one pls explain.

Session timeout means that if a request is not made for certain time (30 min) then user session is deleted/invalidated.

Every AJAX request is of course treated as any other HTTP request and will reset the timeout.

So an app making AJAX requests every 30 seconds, will never reach a session timeout.