Posted by Jerry Stuckle on 08/22/07 11:31

Sanders Kaufman wrote:
> Jerry Stuckle wrote:
>
>
>> Short answer - you can't. You can tell when someone logged on, but
>> not if they're still on the site.
>
>
> Actually, you can. It' called a "beacon" and hackers use it all the time.
>
> The problem is that your more tech-savvy users will see it, and get real
> pissed off. Most folks don't like for you to *monitor* their activity -
> even if you feel that your motives are benign.
>
> There are a number of ways to do it, but the best one seems to be to
> simply have a client-side script that sends a URL request every so often
> to refresh an image (visible or not, but preferably visible - to calm
> techie nerves). For example:
>
> if (sTime > (sNow+15)){
> MyImage.src = "myimage.php?" + sTime + "&" + sToken;
> }
>
> Then, have the PHP file generate the image and log the request.
>
>

Beacons waste bandwidth and give a false sense of accuracy. They are no
more accurate than any other method, and in many ways are LESS accurate.

Get with it. HTML is a stateless protocol. You can guess, but not know.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

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