Websockets are subject to the same origin policy. There's nothing you can do to ...

oefrha · on June 6, 2020

That's not true. You can talk to any other origin with ws. Simple example:

index.html:

  <html>
    <head></head>
    <body>
      <div id="message"></div>
      <script>
        let ws = new WebSocket("ws://localhost:5000/");
        ws.onopen = () => ws.send("hello server!");
        ws.onmessage = ev => {
          const $message = document.getElementById("message");
          $message.textContent = `ws://localhost:5000/ response: ${ev.data}`;
        };
      </script>
    </body>
  </html>

server.js:

  const express = require("express");
  const http = require("http");
  const WebSocket = require("ws");
  
  const app = express();
  const server = http.createServer(app);
  const wss = new WebSocket.Server({ server });
  
  wss.on("connection", ws => {
    ws.on("message", message => {
      console.log(`received: ${message}`);
      ws.send("hello client");
    });
  });
  
  server.listen(5000, () => console.log("ws server listening on localhost:5000"));

Server runs on localhost:5000. Now serve index.html from any other origin and see it talk to the server without any problem.