locking the receive buffer, the buffer is unlocked.
            status.i2.v = NTSRPY( rpyid.i2.r,[rpyflg.i2.r],[rpyadr.i2a.r],
                                  [rpylen.i2.r],[rpysts.i2.r] )
            status.i2.v = NET_SEND_REPLY( rpyid.i2.r,[rpyflg.i2.r],
                                          [rpysts.i2.r] )
         rpyid    word containing the reply identification of the
                  request being answered.
         rpyflg   word containing the reply modifier bits such as LOCKED
                  and ENDMULT.
         rpyadr   address of the buffer which contains the data to be
                  returned to the requestor.  If this is defaulted, then
                  rpylen must also be defaulted or the length must be 0.
         rpylen   word containing the length of the reply message in words.
         rpysts   word containing a specified ACNET global reply status.
                  If this is not given, SUCCESS will be used
                  except when the ENDMULT bit is set in which case the
                  ENDMLT reply status will be used (if the original
                  request had request multiple-replies with MULTRPY).
         status   returns ACNET Global Status (sign-extended to 32-bits):
                      =0 for complete success
                      >0 for conditional success and pending
                      <0 for error condition
         The error codes returned are:
            -02 = local system out of space: no free buffers
            -21 = not connected to network
            -22 = insufficient number of arguments
            -23 = invalid message length: message too long or length
                  is non-zero but no buffer specified.
            -24 = no such request to reply to.
            -25 = illegal event flag
            -26 = request already cancelled
            -28 = not connected for RUM
            -30 = no such logical node
            -43 = system service error: no network process.
            -44 = nontranslatable error: XSC block does not exist
            -45 = internal network error
            -47 = network error #2: no address of reply id word or
                                    not owner of reply control block
            -48 = network error #3:
                - buffer vector in use
                - already waiting for transmission to complete.