Socket.Io how to emit to all members in a room from a socket instance including the sender

How do I emit to all members of a room from a socket instance?

I know I can do io.in('room').emit('event', data); if I have access to the IO instance, but in my case I only have access to the socket of the sender, I store the socket of the user in a user object, and pass it around my code so that I can emit from anywhere, but as a result I have no access to the IO instance.

How can I emit to all members of a room including the sender from the sender’s socket instance?

Answer

Well, it is best to give yourself access to the io instance in some way so you can do io.in(room).emit(...). You can either export it from where you create it and then import it where you are or you can make it available some other way.

Here are four other ways to do it:

Attach .io property to each socket

In the file, where you create the io instance, you can attach it as a property to every socket.

// put io on each socket
io.on('connection', socket => {
    socket.io = io;
});

Then, on any socket, you can get io with socket.io.

---

Put io instance in your app object

If app is available, then some folks put the io instance on the app object with app.set("io", io); so code elsewhere can get it with io.get("io");.

---

Send to both room and self

As a work-around, you could also just send to both:

socket.broadcast(room).emit(...);
socket.emit(...);

---

Use undocumented socket.server

There is also an undocumented property on the socket which gives you access to the server object. Use at your own risk:

socket.server.in("room").emit(...);

which essentially gives you the io instance.