title: What is the "t=" query parameter in a socket.io handshake
body: <p>A socketIO handshake looks something like this :  </p>
  
  <p><code>http://localhost:3000/socket.io/?EIO=3&amp;transport=polling&amp;t=M5eHk0h</code></p>
  
  <p>What is the <code>t</code> parameter? Can't find a explanation.</p>