const { args, listen, copy } = Deno;
const addr = args[1] || "127.0.0.1:4544";
const listener = listen("tcp", addr);
console.log("listening on", addr);
listener.accept().then(
  async (conn): Promise<void> => {
    await copy(conn, conn);
    conn.close();
    listener.close();
  }
);