t_snd(3N)t_snd(3N)NAMEt_snd - send data or expedited data over a connection
SYNOPSIS
#ifdef _XOPEN_SOURCE
#include <xti.h>
#else
#include <tiuser.h>
#endif
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
Page 1
t_snd(3N)t_snd(3N)
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. 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).
This function resides within both the X/Open compliant libxnet and the
SVR4 compliant libnsl Network Services libraries. Network Services
applications which require X/Open compliance must link-load with -lxnet.
Network Services applications which require SVR4 compliance must link-
load with -lnsl.
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 There are multiple conditions which could cause this
t_errno to be generated. One condition is: nbytes
is zero and sending zero bytes is not supported by
the transport provider. Another condition is: if
_XOPEN_SOURCE is defined and a single send was
attempted specifying a TSDU greater than that
specified by the current values of the TSDU field in
the info argument.
TOUTSTATE If _XOPEN_SOURCE is defined and t_snd() is issued in
the wrong sequence on the transport endpoint
referenced by fd, the TOUTSTATE error value is
returned within the variable t_errno.
Page 2
t_snd(3N)t_snd(3N)NOTES
The t_snd routine does not look for a disconnect indication (showing that
the connection was broken) before passing data to the provider.
SEE ALSOt_open(3N), t_rcv(3N)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.
Page 3
