[PlayLSX_Founder]

You could probably do this with a plug-in. Have a look in the plug-in section for an anti-cheat plug-in and see how they do it. You won't be able to stop them connecting if they do not have the client-side package, however, you could maybe add a callback in, something like "AC_OnPlayerMissingClientFiles(playerid);" that you could code under and kick the player or ban them, etc. whatever you wanted to do to them, send them a link to download the client files before kicking them, whatever ..