Challenge 1: Build an Echo Server — Possible Solution
====================================================================

import { WebSocketServer } from "ws";

const wss = new WebSocketServer({ port: 8080 });

wss.on("connection", (socket) => {
  console.log("A client connected.");

  socket.on("message", (data) => {
    const text = data.toString();
    console.log("Received:", text);
    socket.send(text); // send it straight back to THIS client only
  });

  socket.on("close", () => {
    console.log("A client disconnected.");
  });

  socket.on("error", (err) => {
    console.error("Socket error:", err);
  });
});

console.log("Echo server listening on port 8080");

WHY THIS WORKS
--------------
- new WebSocketServer({ port: 8080 }) starts listening for incoming
  WebSocket handshakes on that port — the library takes care of the
  entire Chapter 2 handshake process (Upgrade headers, Sec-WebSocket-Key
  hashing, responding 101 Switching Protocols) automatically.
- The "connection" callback receives a fresh "socket" object for EACH
  client — calling socket.send(text) inside THIS callback sends the
  reply back to only the one client whose message triggered it, since
  "socket" here is scoped to that specific connection, not shared across
  clients.
- data.toString() is necessary because "message" events deliver a
  Buffer by default, not a plain string — sending it back with
  socket.send(text) after converting keeps the echoed reply as readable
  text rather than raw binary.
- Handling "close" and "error" isn't strictly required for the echo
  behavior itself, but it's included here because a server that never
  logs disconnects or errors is much harder to debug once something
  actually goes wrong — a habit worth building from the first server
  you write.