Warning, it is legacy functionality. Nowadays almost nobody configures client computers to not have the access to Internet in games mode. You likely will skip reading this manual chapter.
Client programs working on Windows XP/2003 allow you to use embedded network filter. Unfortunately, this method was disabled in WIndows Vista/7/8 and above. We are working on replacement of this method. Using it, you can deny internet usage in games mode, accurately configure differentiation of games and internet modes. To setup its network filter rules, start client program setup (SetupClient2.exe) and press "Network filter setup" button. Then, you should enable network filter by checking corresponding tick.
Warning! This functionality requires serious network administration skills and could require help of experienced network administrator.
That is how network filter window looks like:
Network filter can be customized for three modes: free, games and internet. Rules can be entered, edited and reordered by pressing corresponding buttons at the top of the window. Rules are processed from top to bottom. Example above shows nine rules. First eight rules allows (forward) network packets using all protocols for program ports 850..853. Last rule blocks all the rest of network traffic. I.e. when computer was not paid for, nothing except client program will work.
Using this functionality you can accurately setup a set of network rules for your cafe. If it is needed, allow games to use network, but deny Internet Explorer (TCP ports 80, 3128, 21 etc) and other programs. You can type all the IP addresses of allowed game servers, ports used by games.
Network rules are stored in file CZ2IPF.cfg. You don't have to setup it for each client computer separately. You should just copy this file from the computer that you had set up to the rest of client computers (to the folder of client program).