How to send error before destroying socket nodejs socket

Question

I'm using the ws library to create a websocket server on nodejs.

the code I'm using:

const express = require('express');
const app = express();
const WebSocket = require('ws');

const server = http.createServer(app);
const wss = new WebSocket.Server({ noServer: true });

wss.on('connection', function connection(ws, request) {
  ws.on('message', function message(msg) {
    console.log(`Received message ${msg} from user ${request.}`);
  });
});

server.on('upgrade', function upgrade(req, socket, head) {
  authenticateServerUpgrade(req, (err, roomCreds) => {
    if (err) {
        socket.write('HTTP/1.1 401 Unauthorized\r\n\r\n');
        socket.destroy();
    }
    wss.handleUpgrade(req, socket, head, ws => {
        req.roomCreds = roomCreds;
        wss.emit('connection', ws, req);
    });
  });
});

server.listen(8080);

Its almost the exact same script from ws. I have implemented the authenticateServerUpgrade() which calls the callback with an error if user is not authenticated.

I want to send this error back to the client so the user knows why the socket was destroyed. I can send it in socket.write, but it doesn't seem to be accessible by socket.onerror in browser. so, is there a better way to do this?

Answer 1

Please try this solution https://stackoverflow.com/a/49775432/3780276

Basically authenticate after the upgrade has been made and send a regular message over the websocket to indicate the error to the client before closing the socket.