TRCVUDATA(3N)             DG/UX 4.30              TRCVUDATA(3N)



     NAME
          t_rcvudata - receive a data unit

     SYNOPSIS
          #include <tiuser.h>

          int trcvudata(fd, unitdata, flags)
          int fd;
          struct tunitdata *unitdata;
          int *flags;

     DESCRIPTION
          This function is used in connectionless mode to receive a
          data unit from another transport user.  Fd identifies the
          local transport endpoint through which data will be
          received, unitdata holds information associated with the
          received data unit, and flags is set on return to indicate
          that the complete data unit was not received.  Unitdata
          points to a t_unitdata structure containing the following
          members:

               struct netbuf addr;
               struct netbuf opt;
               struct netbuf udata;

          The maxlen [see netbufin intro(3)] field of addr, opt, and
          udata must be set before issuing this function to indicate
          the maximum size of the buffer for each.

          On return from this call, addr specifies the protocol
          address of the sending user, opt identifies protocol-
          specific options that were associated with this data unit,
          and udata specifies the user data that was received.

          By default, trcvudata operates in synchronous mode and will
          wait for a data unit to arrive if none is currently
          available.  However, if O_NDELAY is set (via topen or
          fcntl), trcvudata will execute in asynchronous mode and
          will fail if no data units are available.

          If the buffer defined in the udata field of unitdata is not
          large enough to hold the current data unit, the buffer will
          be filled and T_MORE will be set in flags on return to
          indicate that another trcvudata should be issued to
          retrieve the rest of the data unit.  Subsequent trcvudata
          call(s) will return zero for the length of the address and
          options until the full data unit has been received.

          On failure, t_errno may be set to one of the following:

          [TBADF]             The specified file descriptor does not
                              refer to a transport endpoint.



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     TRCVUDATA(3N)             DG/UX 4.30              TRCVUDATA(3N)



          [TNODATA]           O_NDELAY was set, but no data units are
                              currently available from the transport
                              provider.

          [TBUFOVFLW]         The number of bytes allocated for the
                              incoming protocol address or options is
                              not sufficient to store the information.
                              The unit data information to be returned
                              in unitdata will be discarded.

          [TLOOK]             An asynchronous event has occurred on
                              this transport endpoint and requires
                              immediate attention.

          [TNOTSUPPORT]       This function is not supported by the
                              underlying transport provider.

          [TSYSERR]           A system error has occurred during
                              execution of this function.

     SEE ALSO
          intro(3), t_rcvuderr(3N), t_sndudata(3N).

     DIAGNOSTICS
          trcvudata returns 0 on successful completion and -1 on
          failure and t_errno is set to indicate the error.





























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