dWorker(url, {})
          .then(function(message) {
              var pre = document.getElementById('received_message')
              var headers = message.headers;
              pre.innerHTML = "";
              pre.innerHTML += url + ":\n\n";
              pre.innerHTML += JSON.stringify(headers, null, 2) + "\n\n"
              assert_own_property(headers, "host")
              assert_own_property(headers, "connection")
            });
      }, "Worker is responding with HTTP headers");
    </script>

  