How to make private chat on Node JS + Socket.io?

Question

Node.js

How to make a private chat between two users? So that a list of online users is displayed on the side and when you click on one of them, you could correspond with him personally. I've heard that rooms should be used, but I don't fully understand how it works. The very logic.

Answer 1

Or the transferred private message is simply sent to the socket of a specific user, and not to all participants.