How to implement sending a response to a specific client?

Question

Node.js

Let's take a nodejs server with complex work logic. For example, a multiplayer turn-based game: tic-tac-toe or checkers/poker.
An event has occurred and I need to send information about the event to a specific client or group of clients. How are things like this done?

Answer 1

websockets, in the context of node.js I recommend socket.io. Lots of examples.

Answer 2

Socketstream pub/sub I recommend to look at the implementation.