title: How to dissalow modified clients in an open source client-server project?
body: <p>Suppose I have an open source client and server software, both fully open source.</p>
  
  <p>How can I make sure modified clients cannot connect to the un-modified server? Or detect modified clients? For example to prevent cheating in open-source massive multiplayer online games?</p>
  
  <p>I cannot find anything on this subject and excepf for empty google searches I don't know where to start looking for information on this subject so I thought maybe someone here can answer this or even point me in the right direction to get the answer.</p>