[TYPO3] Recognize fe visitors which did not login

[Rens Admiraal]

Hi,

I would like to recognize visitors that are on my website. It is  
meant for the session only.
Typo3 sets a cookie (fe_typo_user) which can be used, and has a  
challenge code in the $_SESSION array, but, on a system on which  
cookies are disabled none of those excist.

Is there a default function in tslib_*** which contains a value that  
is constant for the length of a session? Or do I have to create  
something myself?

Thanks