client.html

<!doctype html>
<html>

<head>
  <title>Test Websocket connection</title>
</head>

<body>
    <span>Test Websocket connection</span>
  <ul>
    <li><button id="closebtn">Close Conn</button></li>
    <li><button id="sendbtn">Send Data</button></li>
  </ul>
  
  
  <script>

    var ws = new WebSocket('ws://127.0.0.1:1201');

    document.getElementById("closebtn").addEventListener('click', ev => {
      ws.close();
    });

    document.getElementById("sendbtn").addEventListener('click', ev => {
      ws.send("Potato")
    });

    ws.onopen = function () {
      ws.send("My test message")
    };

    ws.onclose = function (evt) {
      console.log("Connection closed");
      ws = null;
    }

    // Log errors
    ws.onerror = function (error) {
      console.log('WebSocket Error ' + error);
    };

    // Log messages from the server
    ws.onmessage = function (e) {
        console.log(e.data);
    };


  </script>
</body>

</html>