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t_snd(3c)
t_snd(3C) Standard C Library Functions t_snd(3C)
NAME
t_snd - send data or expedited data over a connection
SYNOPSIS
#include <xti.h>
int t_snd(int fd, void *buf, unsigned int nbytes, int flags);
DESCRIPTION
This routine is part of the XTI interfaces which evolved from the TLI
interfaces. XTI represents the future evolution of these interfaces.
However, TLI interfaces are supported for compatibility. When using a
TLI routine that has the same name as an XTI routine, the tiuser.h
header file must be used. Refer to the TLI COMPATIBILITY section for a
description of differences between the two interfaces.
This function is used to send either normal or expedited data. The ar‐
gument fd identifies the local transport endpoint over which data
should be sent, buf points to the user data, nbytes specifies the num‐
ber of bytes of user data to be sent, and flags specifies any optional
flags described below:
T_EXPEDITED If set in flags, the data will be sent as expedited data
and will be subject to the interpretations of the trans‐
port provider.
T_MORE If set in flags, this indicates 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 (or ETSDU).
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(3C) or t_getinfo(3C), the
T_MORE flag is not meaningful and will be ignored if
set.
The sending of a zero-length fragment of a TSDU or ETSDU
is only permitted where this is used to indicate the end
of a TSDU or ETSDU; that is, when the T_MORE flag is not
set. Some transport providers also forbid zero-length
TSDUs and ETSDUs.
T_PUSH If set in flags, requests that the provider transmit all
data that it has accumulated but not sent. The request
is a local action on the provider and does not affect
any similarly named protocol flag (for example, the TCP
PUSH flag). This effect of setting this flag is proto‐
col‐dependent, and it may be ignored entirely by trans‐
port providers which do not support the use of this fea‐
ture.
Note that the communications provider is free to collect data in a send
buffer until it accumulates a sufficient amount for transmission.
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_NONBLOCK
is set by means of t_open(3C) or fcntl(2), t_snd() will execute in
asynchronous mode, and will fail immediately if there are flow control
restrictions. The process can arrange to be informed when the flow con‐
trol restrictions are cleared by means of either t_look(3C) or the EM
interface.
On successful completion, t_snd() returns the number of bytes (octets)
accepted by the communications provider. Normally this will equal the
number of octets specified in nbytes. However, if O_NONBLOCK is set or
the function is interrupted by a signal, it is possible that only part
of the data has actually been accepted by the communications provider.
In this case, t_snd() returns a value that is less than the value of
nbytes. If t_snd() is interrupted by a signal before it could transfer
data to the communications provider, it returns -1 with t_errno set to
TSYSERR and errno set to EINTR.
If nbytes is zero and sending of zero bytes is not supported by the un‐
derlying communications service, t_snd() returns −1 with t_errno set to
TBADDATA.
The size of each TSDU or ETSDU must not exceed the limits of the trans‐
port provider as specified by the current values in the TSDU or ETSDU
fields in the info argument returned by t_getinfo(3C).
The error TLOOK is returned for asynchronous events. It is required
only for an incoming disconnect event but may be returned for other
events.
RETURN VALUES
On successful completion, t_snd() returns the number of bytes accepted
by the transport provider. Otherwise, -1 is returned on failure and
t_errno is set to indicate the error.
Note that if the number of bytes accepted by the communications
provider is less than the number of bytes requested, this may either
indicate that O_NONBLOCK is set and the communications provider is
blocked due to flow control, or that O_NONBLOCK is clear and the func‐
tion was interrupted by a signal.
ERRORS
On failure, t_errno is set to one of the following:
TBADDATA Illegal amount of data:
o A single send was attempted specifying a TSDU
(ETSDU) or fragment TSDU (ETSDU) greater than
that specified by the current values of the
TSDU or ETSDU fields in the info argument.
o A send of a zero byte TSDU (ETSDU) or zero
byte fragment of a TSDU (ETSDU) is not sup‐
ported by the provider.
o Multiple sends were attempted resulting in a
TSDU (ETSDU) larger than that specified by
the current value of the TSDU or ETSDU fields
in the info argument - the ability of an XTI
implementation to detect such an error case
is implementation-dependent. See WARNINGS,
below.
TBADF The specified file descriptor does not refer to a trans‐
port endpoint.
TBADFLAG An invalid flag was specified.
TFLOW O_NONBLOCK was set, but the flow control mechanism pre‐
vented the transport provider from accepting any data at
this time.
TLOOK An asynchronous event has occurred on this transport
endpoint.
TNOTSUPPORT This function is not supported by the underlying trans‐
port provider.
TOUTSTATE The communications endpoint referenced by fd is not in
one of the states in which a call to this function is
valid.
TPROTO This error indicates that a communication problem has
been detected between XTI and the transport provider for
which there is no other suitable XTI error (t_errno).
TSYSERR A system error has occurred during execution of this
function.
TLI COMPATIBILITY
The XTI and TLI interface definitions have common names but use differ‐
ent header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
Interface Header
The XTI interfaces use the header file, xti.h. TLI interfaces should
not use this header. They should use the header:
#include <tiuser.h>
Error Description Values
The t_errno values that can be set by the XTI interface and cannot be
set by the TLI interface are:
TPROTO
TLOOK
TBADFLAG
TOUTSTATE
The t_errno values that this routine can return under different circum‐
stances than its XTI counterpart are:
TBADDATA
In the TBADDATA error cases described above, TBADDATA is returned, only
for illegal zero byte TSDU ( ETSDU) send attempts.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ MT LevelSafe
SEE ALSO
t_rcv(3C), fcntl(2), t_getinfo(3C), t_look(3C), t_open(3C), attrib‐
utes(7)
WARNINGS
It is important to remember that the transport provider treats all
users of a transport endpoint as a single user. Therefore if several
processes issue concurrent t_snd() calls then the different data may be
intermixed.
Multiple sends which exceed the maximum TSDU or ETSDU size may not be
discovered by XTI. In this case an implementation-dependent error will
result, generated by the transport provider, perhaps on a subsequent
XTI call. This error may take the form of a connection abort, a TSY‐
SERR, a TBADDATA or a TPROTO error.
If multiple sends which exceed the maximum TSDU or ETSDU size are de‐
tected by XTI, t_snd() fails with TBADDATA.
Oracle Solaris 11.4 7 May 1998 t_snd(3C)