title: Expose socket.io listeners after client action
body: <p>Is there a way to set up socket.io listeners for certain clients after they execute a command? For example:</p>
  
  <pre><code>socket.on('setupServer', function (data) {
      console.log("setupServer called");
  
      // Now set up listeners
      socket.on('serverAction', function (data) {
          console.log('Listener for clients calling setupServer');
      });
  
  });
  </code></pre>
  
  <p>In the above, a client has connected and has issued a 'setupServer' command to the node.js server. The server now listens for 'serverAction' from the specific client. Other clients won't be able to use 'serverAction' without calling 'setupServer' first.</p>