Published on

Simple Way to Keep WS Client State in NodeJS


I [previously](/03-05-2019-setting-up-a-basic-websocket-client-server-nodejs/] spoke about how to setup a basic websocket server in NodeJS. One thing that I was not sure about at the time was how to keep track of ws client state on the server side.

It turns out this is fairly simple although not 100% sure how production grade this is:

import uuidv4 from 'uuid/v4';
// wss => web socket server
const wss = new WebSocket.Server({ server });

wss.on('connection', (ws) => {
    //this gets hit when the ws connection is first established
    ws.on('message', (message)=> { = uuidv4();

      //this is hit when the ws receives a message
      // handle message here
      const detail = JSON.parse(message);

      if(detail && detail.type === 'topic-you-expose') {
        ws.clients.forEach((client) => {
            if(client != ws && client.readyState === WebSocket.OPEN){

In the above after the ws.on('message' I assign the websocket client (which has been given the name ws in this case) an id using the uuid library. You can assign any value you want in the above I just called it id by attaching it to the ws object using = uuidv4();. You can then easily access these fields by simply going or ws.yourField.