code: def protocol(self):
          
          proto_id = self.lib.iperf_get_test_protocol_id(self._test)
  
          if proto_id == SOCK_STREAM:
              self._protocol = 'tcp'
          elif proto_id == SOCK_DGRAM:
              self._protocol = 'udp'
  
          return self._protocol
docs: The iperf3 instance protocol
  
          valid protocols are 'tcp' and 'udp'
  
          :rtype: str