Socket.io: How to correctly join and leave rooms

Question

I\'m trying to learn Socket.io by building a set of dynamically created chatrooms that emit \'connected\' and \'disconnected\' messages when users enter and leave. After loo

Answer 1

Socket.IO : recently released v2.0.3

Regarding joining / leaving rooms [read the docs.]

To join a room is as simple as socket.join('roomName')

//:JOIN:Client Supplied Room
socket.on('subscribe',function(room){  
  try{
    console.log('[socket]','join room :',room)
    socket.join(room);
    socket.to(room).emit('user joined', socket.id);
  }catch(e){
    console.log('[error]','join room :',e);
    socket.emit('error','couldnt perform requested action');
  }
})

and to leave a room, simple as socket.leave('roomName'); :

//:LEAVE:Client Supplied Room
socket.on('unsubscribe',function(room){  
  try{
    console.log('[socket]','leave room :', room);
    socket.leave(room);
    socket.to(room).emit('user left', socket.id);
  }catch(e){
    console.log('[error]','leave room :', e);
    socket.emit('error','couldnt perform requested action');
  }
})

Informing the room that a room user is disconnecting

Not able to get the list of rooms the client is currently in on disconnect event

Has been fixed (Add a 'disconnecting' event to access to socket.rooms upon disconnection)

 socket.on('disconnect', function(){(
    /*
      socket.rooms is empty here 
      leaveAll() has already been called
    */
 });
 socket.on('disconnecting', function(){
   // socket.rooms should isn't empty here 
   var rooms = socket.rooms.slice();
   /*
     here you can iterate over the rooms and emit to each
     of those rooms where the disconnecting user was. 
   */
 });

Now to send to a specific room :

// sending to all clients in 'roomName' room except sender
  socket.to('roomName').emit('event', 'content');

Socket.IO Emit Cheatsheet

Answer 2

This is how I inform users of a "disconnecting user"

socket.on('disconnecting', function(){
        console.log("disconnecting.. ", socket.id)
        notifyFriendOfDisconnect(socket)
    });

function notifyFriendOfDisconnect(socket){
    var rooms = Object.keys(socket.rooms);
    rooms.forEach(function(room){
        socket.to(room).emit('connection left', socket.id + ' has left');
    });
}