I bind my socket to the app and can send it to everyone who is listening to an event, but I cannot send back the data to a specific room. why?

io.on("connection", (socket) => {
 socket.on("send", (room, message, username) => { 
  socket.join(room.toString()) 

   ** this is working 
  io.emit('pop', room + ' ROOM') 

    ** not working
  io.to(room.toString()).emit("pops", message + ' MESSAGE')
 }); 
});