<!DOCTYPE HTML>
<html>
<body>
  <script type="application/javascript">

  function ok(what, msg) {
    window.parent.postMessage({type: what ? 'OK' : 'KO', msg }, '*');
  }

  window.addEventListener('message', receiveMessage);
  function receiveMessage(evt) {
    if (evt.data.type == 'PORT') {
      var port = evt.data.port;
      var counter = 0;
      port.onmessage = function(event) {
        if (counter++ == 0) {
          ok(!(event.data % 2), "The number " + event.data + " has been received correctly by the iframe");

          window.parent.postMessage({ type: 'PORT', port }, '*', [port]);
        }
        else {
          ok(false, "Wrong message!");
        }
      }
    } else {
      ok(false, "Unknown message");
    }
  }

  </script>
</body>
</html>
