Return information about the request or USM.
            status.i2.v = NTWREQ( rpyid.i2.r,[lenadr.i2.r],[nodadr.i2.r],
                                  [srcadr.i1a.r] )
            status.i2.v = NET_WAIT_REQUEST( rpyid.i2.r,[lenadr.i2.r],
                                             [reqid.i2.r],[srcadr.i1a.r] )
         rpyid    word to receive the reply identification code of
                  the received request (will be set to 0 for a USM).
         lenadr   word to receive the length of the request or USM
                  message (in words).
         nodadr   word to receive the destination logical trunk and node.
                  The trunk (also known as LAN id) will be stored in
                  the upper byte of this word.
         flgadr   byte to receive the request flags and the message
                  type code.
         reqid    word to receive the request identification of the
         srcadr   word to receive the source logical node and source
                  logical task id (high byte) bytes.
         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:
            +01 = Pending: receive buffer is unlocked and empty.
            -21 = not connected to the network
            -22 = insufficient number of arguments
            -28 = this task not connected for RUM
            -29 = local locked receive buffer: receive buffer locked
                  by an "old" USM or a Request that does not exist any more.
            -31 = truncated request
            -43 = system service error: no network process
            -44 = nontranslatable error: no XSC block.
            -45 = internal network error
            -47 = network error #2: no address for a reply id or not
                                    owner of reply control block