code: def indication(self, pdu):
          
          if _debug: Node._debug("indication(%s) %r", self.name, pdu)
  
          # make sure we're connected
          if not self.lan:
              raise ConfigurationError("unbound node")
  
          # if the pduSource is unset, fill in our address, otherwise
          # leave it alone to allow for simulated spoofing
          if pdu.pduSource is None:
              pdu.pduSource = self.address
          elif (not self.spoofing) and (pdu.pduSource != self.address):
              raise RuntimeError("spoofing address conflict")
  
          # actual network delivery is a zero-delay task
          OneShotFunction(self.lan.process_pdu, pdu)
docs: Send a message.