Using socket.io

  1. insall socket.io
npm i socket.io -S
  1. make files

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <script src="<https://cdn.socket.io/socket.io-3.0.1.min.js>"></script>
    <title>Hello Socket.io!</title>
  </head>
  <body>
    <script>
      const socket = io("ws://localhost:3000");
      socket.on("connect", () => {
        socket.send("Hello!");
      });

      socket.on("message", (data) => {
        console.log(data);
      });
    </script>
  </body>
</html>

app.js

const socketIo = require("socket.io");

const io = socketIo(3000);
  1. Save and Open html file

: Errors are normal because it's not a valid url. It's fine.

Make server can handle socket

app.js

const socketIo = require("socket.io");

const io = socketIo(3000, {
    cors: {
        origin: "*",
        methods: ["GET", "POST"]
    }
});