T_SND(3N)                            SysV                            T_SND(3N)



NAME
     t_snd - send data or expedited data over a connection

SYNOPSIS
     #include <tiuser.h>

     int t_snd(fd, buf, nbytes, flags)
     int fd;
     char *buf;
     unsigned nbytes;
     int flags;

DESCRIPTION
     This function is used to send either normal or expedited data.  fd
     identifies the local transport endpoint over which data should be sent,
     buf points to the user data, nbytes specifies the number of bytes of user
     data to be sent, and flags specifies any optional flags described below.

     By default, t_snd operates in synchronous mode and may wait if flow
     control restrictions prevent the data from being accepted by the local
     transport provider at the time the call is made.  However, if O_NDELAY is
     set (via t_open or fcntl), t_snd will execute in asynchronous mode, and
     will fail immediately if there are flow control restrictions.

     On successful completion, t_snd returns the number of bytes accepted by
     the transport provider.  Normally this will equal the number of bytes
     specified in nbytes.  However, if O_NDELAY is set, it is possible that
     only part of the data will be accepted by the transport provider.  In
     this case, t_snd will set T_MORE for the data that was sent (see below)
     and will return a value less than nbytes.  If nbytes is zero, no data
     will be passed to the provider and t_snd will return zero.

     If T_EXPEDITED is set in flags, the data will be sent as expedited data,
     and will be subject to the interpretations of the transport provider.

     If T_MORE is set in flags, or set as described above, an indication is
     sent to the transport provider that the transport service data unit
     (TSDU) (or expedited transport service data unit -  ETSDU) is being sent
     through multiple t_snd calls.  Each t_snd with the T_MORE flag set
     indicates that another t_snd will follow with more data for the current
     TSDU.  The end of the TSDU (or ETSDU) is identified by a t_snd call with
     the T_MORE flag not set.  Use of T_MORE enables a user to break up large
     logical data units without losing the boundaries of those units at the
     other end of the connection.  The flag implies nothing about how the data
     is packaged for transfer below the transport interface.  If the transport
     provider does not support the concept of a TSDU as indicated in the info
     argument on return from t_open or t_getinfo, the T_MORE flag is not
     meaningful and should be ignored.

     The size of each TSDU or ETSDU must not exceed the limits of the
     transport provider as returned by t_open or t_getinfo.  Failure to comply
     will result in protocol error EPROTO.  (See TSYSERR below.)

     If t_snd is issued from the T_IDLE state, the provider may silently
     discard the data.  If t_snd is issued from any state other than
     T_DATAXFER or T_IDLE, the provider will generate an EPROTO error.

DIAGNOSTICS
     On successful completion, t_snd returns the number of bytes accepted by
     the transport provider, and it returns -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.

     [TFLOW]             O_NDELAY was set, but the flow control mechanism
                         prevented the transport provider from accepting data
                         at this time.

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

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

SEE ALSO
     t_open(3N), t_rcv(3N)
     Programming with the SysV Transport Interface