SocketIO 3 -> Server API -> get socket objects by ID?

[tgbv]

According to docs I can do:

await io.of('/').allSockets()

....and receive all connected socket IDs.

But how to retrieve the actual socket objects based on those IDs? 🤔

[darrachequesne]

You can use the namespace#sockets attribute:

for (const [id, socket] of io.of("/").sockets) {
  console.log(id, socket.handshake);
}

Please note that this Map contains only the socket instances on the current Socket.IO server, while the allSockets() method returns all socket IDs across multiple Socket.IO servers.

[tgbv]

Thank you for reply!

contains only the socket instances on the current Socket.IO server
[ ... ]
across multiple Socket.IO servers

By "socketio server" you mean socket namespace?

[darrachequesne]

In the following example:

Running:

for (const [id, socket] of io.of("/").sockets) {
  console.log(id, socket.handshake);
}

on Server A will loop on 2 Socket instances (Client 1 & 2).

But:

const ids = await io.of("/").allSockets();

will return 3 Socket IDs (provided that you use the Redis adapter).

Documentation: https://socket.io/docs/v3/using-multiple-nodes/

This is also true for other namespaces:

// loop on the "local" socket instances
for (const [id, socket] of io.of("/admin").sockets) {
  console.log(id, socket.handshake);
}
// fetch all the IDs across Socket.IO servers
const ids = await io.of("/admin").allSockets();

Documentation: https://socket.io/docs/v3/namespaces/

[tgbv]

Understood! Thank you