t_snd(3N)                        DG/UX 5.4.2                       t_snd(3N)


NAME
       t_snd - send data or expedited data over a connection

SYNOPSIS
       #include <tiuser.h>

       int t_snd (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 or O_NONBLOCK is set (via t_open or fcntl), t_snd will
       execute in asynchronous mode, and will fail immediately if there are
       flow control restrictions.

       Even when there are no flow control restrictions, t_snd will wait if
       STREAMS internal resources are not available, regardless of the state
       of O_NDELAY or O_NONBLOCK.

       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 or O_NONBLOCK 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 and sending of zero bytes is not supported
       by the underlying transport provider, t_snd() will return -1 with
       t_errno set to TBADDATA.  A return value of zero indicates that the
       request to send a zero-length data message was sent to the provider.

       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 is 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



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t_snd(3N)                        DG/UX 5.4.2                       t_snd(3N)


       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.  If the size
       is exceeded, a TSYSERR with system error EPROTO will occur.  However,
       the t_snd may not fail because EPROTO errors may not be reported
       immediately.  In this case, a subsequent call that accesses the
       transport endpoint will fail with the associated TSYSERR.

       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, T_INREL or T_IDLE, the provider will generate a TSYSERR
       with system error EPROTO (which may be reported in the manner
       described above).

       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 or O_NONBLOCK 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 [see intro(2)] has been detected
                           during execution of this function.

       [TBADDATA]          nbytes is zero and sending zero bytes is not
                           supported by the transport provider.

SEE ALSO
       t_open(3N), t_rcv(3N).
       UNIX System V Network Programmer's Guide.

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.
















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