asp.net periodically send messages to server
<p>I'm using VS2010,C# for developing ASP.NET. I want to send periodical messages to server in order that server knows which user is really active (with open windows), so that when a user closes window or changes url (instead of clicking on logout button), my server can detect user sign out and can close his session. what are my options here? I don't think JavaScript would be safe as I should probably update my database (is there any other way? for instance can I call an address in my JS function?)</p>

<p>Another solution would be to use AJAX to send server side messages to server, is it safe and efficient? what is the best way? security is really important for me</p>
