You’ve pretty much figured it out. Only the server can emit to specific rooms, because it is only the server that is actually connected to multiple clients. In other words, clients aren’t connected to each other — the client-side library only manages communications between that one client and the server. So, if you want your client app to instruct the server to emit a message to all clients connected to a given room… that’s basic API design. You could emit a socket event, or just do a regular http call to a route on your server. Either way you’ll be sending metadata about which room(s) the server should broadcast to. The former (emitting) is probably preferred however, because that way on the server side you can use socket.broadcast.to to emit to all clients in the room EXCEPT the socket that initiated the call (a pretty common use case).