title: socket io rooms names and number of users inside specific room
body: <p>I'm trying to build some basic chat (based with rooms) using socket.io versions:</p>
  
  <pre><code>"socket.io": "^2.1.1"
  "socket.io-client": "^2.1.1"
  </code></pre>
  
  <p>I have a few basic questions that I couldn't find any working answers no matter how deep I looked for them.</p>
  
  <ol>
  <li><p>When a user gets in a specific room I'm doing it (in the server)
  <code>socket.join(roomName)</code> so the room 'exists' only if there is at least on socket connected to this room ?</p></li>
  <li><p>I want to create a screen with the rooms name and the number of the participates - (is it possible to get it by the client side socketIO's object ?), I found that it's possible to get the rooms names(server-side) by using <code>io.sockets.adapter.rooms</code> but I get really weird strings which are definitely not the room names.    </p></li>
  <li><p>I'm trying to create a page inside each room that shows the users that are connected to that room (connection that got into a room with <code>socket.join(roomName)</code>)</p></li>
  </ol>
  
  <p>I'm new to socket.io I hope someone can help me to understand better how to work with that, and what I'm missing in here. </p>
  
  <p>thanks!</p>