Socket.io has a really good example how to implement a simple chat with private rooms (1:1)
- https://socket.io/get-started/private-messaging-part-1/
- https://socket.io/get-started/private-messaging-part-2/
- https://socket.io/get-started/private-messaging-part-3/
- https://socket.io/get-started/private-messaging-part-4/
Github repo https://github.com/socketio/socket.io/tree/master/examples/private-messaging
