code: def stop(self, now=False):
          
          if now:
              self.shutdown_immediately = True
          else:
              self.shutdown_gracefully = True
docs: Stop the server gracefully. Do not take any new transfers,
          but complete the existing ones. If force is True, drop everything
          and stop. Note, immediately will not interrupt the select loop, it
          will happen when the server returns on ready data, or a timeout.
          ie. SOCK_TIMEOUT