Socket.io + Redis - clients are joining each others' "private" rooms

Question

I've just started working with Socket.io and Redis for pub/sub messaging and it's pretty great. One important feature of my application is that the server needs to be able to broadcast messages to all subscribers of a room, and also choose 1 subscriber in that room and narrowcast a message just to them. For now, that subscriber is chosen at random. Based on reading socket.io's documentation, I think I can accomplish this.

However, I've come across something I don't understand. In Socket.io's Default Room documentation (https://socket.io/docs/rooms-and-namespaces/#default-room), they say that each socket automatically joins a room named after its socket ID. This looks like it would solve my narrowcast requirement -- look at the list of client IDs connected to my "big" room, choose one at random, and then send a message to the room with the same name as the chosen ID.

However, it doesn't work because for some reason all clients are joining each others' default rooms. I'm not seeing any exceptions in my code, but my "narrowcast" messages are going to all clients.

Here's my server-side code:

var io = require('socket.io');
var redisAdapter = require('socket.io-redis');
var server = io();

server.adapter(redisAdapter({ host: 'localhost', port: 6379 }))

server.on('connect', (socket) => {
  console.log(`${socket.id} connected!`);
  socket.join('new');
  server.emit('welcome', `Please give a warm welcome to ${socket.id}!`);
  server.to(socket.id).emit('private', 'Just between you and me, I think you are going to like it here');
});

server.listen(3000);

setInterval(whisperAtRandom, 2000);

function whisperAtRandom() {
  server.in('new').adapter.clients((err, clients) => {
    if (err) throw err;

    console.log('Clients on channel "new": ', clients);
    chosenOne = clients[Math.floor(Math.random()*clients.length)];
    console.log(`Whispering to ${chosenOne}`);
    server.to(chosenOne).emit('private', { message: `Psssst... hey there ${chosenOne}`});
    server.in(chosenOne).adapter.clients((err, clients) => {
      console.log(`Clients in ${chosenOne}: ${clients}`)
    })
  });
}

It stands up the server, listens on port 3000, and then every 2 seconds sends a message to a random client in the "new" room. It also logs out the list of clients who are connected to the "new" room and the "" room.

Here's the client-side code:

var sock = require('socket.io-client')('http://localhost:3000');

sock.connect();

sock.on('update', (data) => {
  console.log('Updating...');
  console.log(data);
});

sock.on('new', (data) => {
  console.log(`${sock.id} accepting request for new`);
  console.log(data.message);
});

sock.on('welcome', (data) => {
  console.log('A new challenger enters the ring');
  console.log(data);
});

sock.on('private', (data) => {
  console.log(`A private message for me, ${sock.id}???`);
  console.log(data);
});

My problem is that all my clients are connected to each others' "" room. Here's a sample from my logs:

0|socket-s | Clients on channel "new":  [ 'dJaoZd6amTfdQy5NAAAA', 'bwG1yTT46dr5R_G6AAAB' ]
0|socket-s | Whispering to bwG1yTT46dr5R_G6AAAB
2|socket-c | A private message for me, dJaoZd6amTfdQy5NAAAA???
2|socket-c | Psssst... hey there bwG1yTT46dr5R_G6AAAB
1|socket-c | A private message for me, bwG1yTT46dr5R_G6AAAB???
1|socket-c | Psssst... hey there bwG1yTT46dr5R_G6AAAB
0|socket-s | Clients in bwG1yTT46dr5R_G6AAAB: dJaoZd6amTfdQy5NAAAA,bwG1yTT46dr5R_G6AAAB

You can see that the "private" message is received by both clients, dJaoZ... and bwG1y..., and that both clients are connected to the default room for bwG1y....

Why is this? Does it have something to do with the fact that both of my clients are running on the same machine (with different Node processes)? Am I missing something in Socket.io's documentation? Any help is appreciated!

PS -- to add even more confusion, the private messaging that occurs in server.on('connect', ... works! Each clients receives the "Just between you and me ..." message exactly once, right after they connect to the server.

Answer 1

Your main problem could caused by server.to in whisperAtRandom function, use socket instead of server for the private message:

socket.to(chosenOne).emit('private', { message: `Psssst... hey there ${chosenOne}`});

To answer your other problems, try to change these:

server.emit('welcome', `Please give a warm welcome to ${socket.id}!`);
server.to(socket.id).emit('private', 'Just between you and me, I think you are going to like it here');

To:

socket.broadcast.emit('welcome', `Please give a warm welcome to ${socket.id}!`);
socket.emit('private', 'Just between you and me, I think you are going to like it here');

Check out my Socket.IO Cheatsheet:

// Socket.IO Cheatsheet

// Add socket to room
socket.join('some room');

// Remove socket from room
socket.leave('some room');

// Send to current client
socket.emit('message', 'this is a test');

// Send to all clients include sender
io.sockets.emit('message', 'this is a test');

// Send to all clients except sender
socket.broadcast.emit('message', 'this is a test');

// Send to all clients in 'game' room(channel) except sender
socket.broadcast.to('game').emit('message', 'this is a test');

// Send to all clients in 'game' room(channel) include sender
io.sockets.in('game').emit('message', 'this is a test');

// sending to individual socket id
socket.to(socketId).emit('hey', 'I just met you');