Remembering a client even after they disconnect nodeJS socket.io

Question

I have a chat app and currently, the client is saving its name in a text file, this works fine for windows but mac has some weird directory settings so it makes it harder to read the text file. I'm wondering if it's possible that when a client connects my server saves their IP or some sort of constant data about the client so when the client connects again I can know who it is and assign the name accordingly.

I'm using nodeJS socket.io

Answer 1

First thing that comes to my mind is to make the client responsible for identifying itself by sending a generated UUID to server after connecting

socket.on("connect", () => {
  const CLIENT_UUID = 'uuid';
  // Get client UUID from local storage
  let clientUuid = localStorage.getItem(CLIENT_UUID);

  // Check whether if this is a new client and it doesn't have UUID
  if (!clientUuid) {
    // Then generate random UUID, you'll need to implement `generateRandomUuid`
    clientUuid = generateRandomUuid();
    // Then save it to local storage
    localStorage.setItem(CLIENT_UUID, clientUuid);
  }

  // Then just emit the connected event
  // This will be the actual connection event as once this is emitted and received
  socket.emit('connected', {
    uuid: clientUuid
  });
});

Now on server you can handle the client based on it's UUID

io.on('connection', (socket) => {
  // Here you handle the `connected` event
  socket.on('connected', (clientUuid) => {
    // And now you can handle this clientUuid
    const chats = getCurrentClientChats(clientUuid);
    const groups = getCurrentClientGroups(clientUuid);

    socket.emit('current-chats', { chats });
    socket.emit('current-groups', { groups });
  });
});

Notice that way, you'r client is now actually known on the connected event

Same approach but probably cleaner is to send the client UUID upon connecting to the server, since it's really easy to do that with socket IO

const socket = io("ws://example.com/my-namespace", {
  query: { clientUuid }
});

And just use it upon connection

io.on('connection', (socket) => {
  const clientUuid = socket.handshake.query.name;
  const chats = getCurrentClientChats(clientUuid);
  const groups = getCurrentClientGroups(clientUuid);

  socket.emit('current-chats', { chats });
  socket.emit('current-groups', { groups });
});