index.html

<html>
    <head>
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <style>
            body {
               background: #ccc; 
            }
            iframe {
                display: block;
                margin: 100px auto 0 auto;
                border: 1px solid black;
                height: 500px;
                width: 400px;
            }
        </style>
    </head>
    <body>
        <iframe src="https://enke.to/i/widgets?parentWindowOrigin=http%3A%2F%2Fenketo.github.io"></iframe>

        <script>
            window.addEventListener("message", receiveMessage, false);

            function receiveMessage(event)
            {
              // TODO in real life, check origin! if (event.origin !== "http://enk.to:8080") return;
              console.log('data received from iframe', JSON.parse(event.data));
              console.log('origin of message', event.origin);
              console.log('source of message', event.source);
            }
        </script>
    </body>
</html>