T_RCVUDATA(3N)                       SysV                       T_RCVUDATA(3N)



NAME
     t_rcvudata - receive a data unit

SYNOPSIS
     #include <tiuser.h>

     int t_rcvudata(fd, unitdata, flags)
     int fd;
     struct t_unitdata *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 netbuf in 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, t_rcvudata 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 t_open or fcntl), t_rcvudata 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 t_rcvudata should be
     issued to retrieve the rest of the data unit.  Subsequent t_rcvudata
     call(s) will return zero for the length of the address and options until
     the full data unit has been received.

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

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

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

     [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)
     Programming with the SysV Transport Interface