Create and join custom chat rooms stored in mongodb with Node.js and Socket.IO Rooms

I'm starting to develop a chat app for mobile devices and I've decided to use Node.js plus Socket.IO to build the main functionality. Basically, what I want to achieve is a private messaging system between users and chat groups that can be created by the users. Everybody can join into a chat room, and those rooms are going to be stored into mongodb. For creating the rooms in the database, I'm going to use Express with a simple request with the basic data (room name, description).

I'm pretty new to all the Node.js/Socket.IO, so I don't know exactly where do I have to query the database about all the available rooms. What I thought is the following thing:

1. Use Express to get a JSON list of available chat rooms.
2. List all the chat rooms available. Tap on one of them and

3. Get the chat room 'name' or 'id' and use to do the following

   io.sockets.on('connection', function (socket, room) {
       socket.join(room);
       socket.broadcast.to(room).send('Hello room!');
   });
   

I will have to do the connection when the user selects a room, am I right? If so, the room is going to be the token for the connection?