How to send data to a specific user via socket.io?

Question

JavaScript

Hello everyone
In general, there is a game where users do various actions.
All actions are processed and data is transferred to the database of users, but I don’t know how to transfer exactly its data from the database through sockets and so that it displays the changes, if any
. need to show these changes in
real time Authorization done by jwt + passport.js
Please help

Answer 1

We store in memory (or cache) a "table" with connection and user associations. When connected, the table is replenished, when disconnected, the necessary records are deleted accordingly. When an event occurs, we look for all its connections and for each helmet the same message.

Answer 2

When reporting from a specific socket, return the message to the socket, not to the server.
server:

io.on('connect', function(socket) {
  socket.emit('message','Учите документацию!');
});

client:

socket.on('message', function(data) {
  console.log(data);
});