multithreading http server

I have completed and tested http_server application for single user/ thread. Application asks  the user couple of questions.  Eaqch in different screen. Since the next question is based on processing current information But when I changed to multi threaded application by using
:- use_module(library(http/thread_httpd)),  
each screen has different session ID, thus I can not collect informations using http_session_dat, http_session_assert, http_session_retract.

Please advice, how to have a session per user. I run on Mac OS X , Snow Leopard with stable 6.6 version

Thanks Josef Frydl