socket.io - how to broadcast messages on a namespace?

Question

According to socket.io examples:

To broadcast, simply add a broadcast flag to emit and send method calls. Broadcasting means sending a message to everyone else except for the socket that starts it.

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
  socket.broadcast.emit('user connected');
});

I tried to combine this with the new socket.io namsepace feature, so I got this:

var chat = ioserver.of('/chat');

chat.on('connection', function (socket) {
      console.log('chat connection');   
      socket.on('message', function (msg) {
        console.log(msg);  
        chat.send(msg);
      });
  });

This works fine, everyone on the chat channel (and no other channels) gets the message. But the sender also gets it. So I tried to do the following:

chat.on('connection', function (socket) {
      console.log('chat connection');   
      socket.on('message', function (msg) {
        console.log(msg);  
        chat.broadcast.send(msg);
      });
  });

and got an Exception: 'Cannot call method 'send' of undefined.' Ok, so I thought, that broadcast is the feature of a single socket (it feels a bit weird though - how a single socket can brodacast to all other...). So I tried:

chat.on('connection', function (socket) {
      console.log('chat connection');   
      socket.on('message', function (msg) {
        console.log(msg);  
        socket.broadcast.send(msg);
      });
  });

but now it was even worse - no one received the message, not even the sender. Anyway, it was what I logically expected - one socket cannot broadcast something through itself. And no exceptions this time, so broadcast is defined for the socket.

If I do:

chat.on('connection', function (socket) {
      console.log('chat connection');   
      socket.on('message', function (msg) {
        console.log(msg);  
        socket.send(msg);
      });
  });

then only the original sender gets the message, and that is again pretty logical - I used the 'send' of the client-related socket.

So the question is: what is the correct way to use the broadcast feature?

Maybe the developer of socket.io made a mistake and added the broadcast feature to the wrong object (as I understand, it should be the feature of the namespace but now it is defined only for the socket)?

Answer 1

Seems I was able to solve this for myself after opening a bounty. Sorry about that.

Anyway, see if this helps:

chat.on('connection', function (socket) {
  socket.on('message', function (msg) {
    socket.emit(msg); // Send message to sender
    socket.broadcast.emit(msg); // Send message to everyone BUT sender
  });
});

However, you could save some bandwidth and create a more snappy experience for users if you don't resend it to the sender. Just add their messages directly to the chat log, and optionally use use only self-emit to confirm it was received without issue.

Answer 2

You solution works if you are working in an evented environment where messages from the client trigger a response to all others, but not if you want the server to sent messages to all clients.

You can do this using io.sockets.emit:

var io = require('socket.io').listen(80);
io.sockets.emit('message', { message: "Hello everyone!" });

However the documentation isn't clear for how to do this to a specific namespace. io.sockets is just a shortcut to io.of(''), as such you can broadcast to everyone on a namespace by calling io.of('/namespace').emit:

var io = require('socket.io').listen(80);
io.of('/admins').emit('message', { message: "Hello admins!" });

Answer 3

var customNS = ioserver.of('/chat'); 

customNS.on('connection', function (socket) {
   socket.on('message', function (msg) {

       // Send message to sender 
       socket.emit(msg);

       // Send message to everyone on customNS INCLUDING sender
       customNS.emit(msg);

       // Send message to everyone on customNS BUT sender
       socket.broadcast.emit(msg);

       // Send message to everyone on ROOM chanel of customNS INCLUDING sender
       customNS.in('ROOM').emit(msg); 

       // Send message to everyone on ROOM chanel of customNS BUT sender
       socket.broadcast.in('ROOM').emit(msg); 


   });
});

also check this answer Send response to all clients except sender (Socket.io)

Answer 4

Maybe this will help someone

socket.broadcast.to('room1').emit('updatechat', 'SERVER', username + ' has connected to this room'); 

see

Nodejs and Socketio Multiroom Chat Tutorial