title: With AFNetworking in iOS, what is the best way to determine if a failure response is a server error or connection error?
body: <p>With AFNetworking in iOS, what is the best way to determine if a failure response is a server error or connection error?</p>
  
  <p>For example, if an upload fails due to a connection error, I may want to retry the upload automatically after some time interval.  Conversely, if an upload fails because of a server error, I will want to permanently stop trying the request.  (Errors where I would NOT want to retry would be most 400 and 500 errors.)</p>
  
  <p>Please tell me how can I most easily determine if I'm simply seeing a connection error or if I am seeing a server error? </p>