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T_RCVUDATA(3N)                                                  T_RCVUDATA(3N)



NAME
       t_rcvudata - receive a data unit

SYNOPSIS
       #include <&lt;tiuser.h>&gt;

       int t_rcvudata(fd, unitdata, flags)
       int fd;
       struct t_unitdata *unitdata;
       int *flags;

DESCRIPTION
       t_rcvudata() 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 associ-
       ated with the received data unit, and flags is set on return  to  indi-
       cate  that the complete data unit was not received.  unitdata points to
       a t_unitdata structure defined in <&lt;nettli/tiuser.h>&gt; as:
              struct t_unitdata {
                   struct netbuf addr;             /* address        */
                   struct netbuf opt;              /* options        */
                   struct netbuf udata;            /* user data      */
              };

       The maxlen, len, and buf members of the netbuf structure are  described
       in  t_accept(3N).  The maxlen field of addr, opt, and udata must be set
       before issuing t_rcvudata() 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  asso-
       ciated  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 (using t_open(3N) or fcntl()), t_rcvudata()  will  exe-
       cute 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_rcvu-
       data() should be issued to retrieve the rest of the data unit.   Subse-
       quent  t_rcvudata()  call(s)  will  return  zero  for the length of the
       address and options until the full data unit has been received.

RETURN VALUES
       t_rcvudata() returns:

       0      on success.

       -1     on failure and sets t_errno to indicate the error.

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

       TBUFOVFLW           The number of bytes allocated for the incoming pro-
                           tocol 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  trans-
                           port endpoint and requires immediate attention.

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

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

       TSYSERR             The  function  failed due to a system error and set
                           errno to indicate the error.

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

                                21 January 1990                 T_RCVUDATA(3N)