title: How to prevent login more than once from same user in nodejs chat application?
body: <p>I'm using <code>Socket.io</code> and <code>Express</code> to make a chat application. </p>
  
  <p>The chat is anonymous and I don't want to save anything in any database. I can think of checking the IP address of the user and prevent another login from the same IP address, but I don't think that's a good idea, because people are online with shared IP addresses. Another thing would be session id, but that changes even when the user logs in from a different tab in browser. Is there any easy way to do this without using any database? Preferably without installing any other package/lib? </p>