Need to capture actual session time - help!

Question

I am trying to capture the time a user is on the actual site.
I tried using onSessionEnd in my application.cfc but that just
drops in the time of the actual last click variable I set and when
the session times out. I don't capture the actual time the person
left the site. I don't want to use short timeout values because the
site has some very long pages to read and someone could spend 30
minutes on the page. Is there a way to have a hidden layer or
graphic that keeps an open connection with the browser and the
server so I can use short timeout values and not worry about the
person just sitting there on one page reading? I also need to make
sure whatever method is the most browser friendly and as
unnoticeable by the user as possible. Thanks!

Answer 1

You could use AJAX to ping a back-end page to keep your
session alive. You would need to have a javascript run every x
seconds firing the AJAX call. Something like (not full script just
an example):
<script type="text/javascript">
// Every 10 seconds call the keepAlive function
window.setInterval("keepAlive('<cfoutput>#session.CFID#</cfoutput>')",10000);
function keepAlive(sessionid){
//do ajax keep alive call here (i.e. call to keepalive.cfm)
</script>