title: Sending message to specific group of clients in socketio
body: <p>What's the best way to send a message via socket io to a group of users, for example only those in a specific chat room instead of all users?</p>
  
  <p>I am aware of <a href="https://stackoverflow.com/questions/4943573/sending-data-only-to-chosen-users-using-socket-io-node">Sending data only to chosen users using Socket.io-node</a> but socketio version .7 was released recently and seems like there might be a more elegant way with the new api using either get/set or namespacing?</p>