code: def process_npdu(self, npdu):
          
          if _debug: NetworkAdapter._debug("process_npdu %r (net=%r)", npdu, self.adapterNet)
  
          pdu = PDU(user_data=npdu.pduUserData)
          npdu.encode(pdu)
          self.request(pdu)
docs: Encode NPDUs from the service access point and send them downstream.