Cannot read property 'protocol' of undefined

This error occurs when something goes wrong in request, for ex. if you set url as undefined, invalid method, or invalid content type, anything wrong with request object will throw this error.

You're issuing a malformed $http request.

You are not supposed to set your headers in a separate call to $http. Call to $http() will actually issue the request, but since you configured it with just the header (no url or method), it throws that error at you (as expected).

If you want to set your header you'll want to do that by passing a custom config object as a second parameter to your $http.get() call:

$http.get(url, {
  headers: {
    'Content-type': 'application/json'
  }
}).success(function (events) {
  $scope.events = events;
});