NAME [Toc] [Back]
t_sndudata() - send a data unit
SYNOPSIS [Toc] [Back]
#include <xti.h> /* for X/OPEN Transport Interface - XTI */
/* or */
#include <tiuser.h> /* for Transport Layer Interface - TLI )
int t_sndudata(fd, unitdata);
struct t_unitdata *unitdata;
DESCRIPTION [Toc] [Back]
The t_sndudata() function is used in connectionless mode to send a
data unit to another transport user. The argument fd identifies the
local transport endpoint through which data is sent. The argument
unitdata points to a type t_unitdata structure used to specify a data
unit being sent through the transport endpoint specified by the fd
parameter. The t_unitdata structure has the following members:
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
The type netbuf structure is defined in the <xti.h> or <tiuser.h>
header file. This structure, which is used to define buffer
parameters, has the following members:
unsigned int maxlen maximum byte length of the data buffer
unsigned int len actual byte length of data written to
char *buf points to buffer location
In unitdata, addr specifies the protocol address of the destination
user, opt identifies protocol-specific options that the user wants
associated with this request and udata specifies the user data to be
sent. The user may choose not to specify what protocol options are
associated with the transfer by setting the len field of opt to zero.
In this case, the provider may use default options.
If the len field of udata is zero, and sending of zero octets is not
supported by the underlying transport service, the t_sndudata() will
return -1 with t_errno set to [TBADDATA].
By default, t_sndudata() executes in the synchronous operating 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 (via t_open() or fcntl()), t_sndudata()
will execute in asynchronous mode and will fail under such conditions.
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The process can arrange to be notified of the clearance restriction
via either t_look() or the EM interface.
If the amount of data specified in udata exceeds the TSDU size as
returned in the tsdu field of the info argument of t_open() or
t_getinfo(), a [TBADDATA] error will be generated. If t_sndudata() is
called before the destination user has activated its transport
endpoint, the data unit may be discarded.
If it is not possible for the transport provider to immediately detect
the conditions that cause errors [TBADADDR] and [TBADOPT], then these
errors will alternatively be returned by t_rcvuderr(). Therefore, an
application must be prepared to receive these errors both of these
Thread-Safeness [Toc] [Back]
The t_sndudata() function is safe to be called by multithreaded
applications, and it is thread-safe for both POSIX Threads and DCE
User Threads. It has a cancellation point. It is neither asynccancel
safe nor async-signal safe. Finally, it is not fork-safe.
RETURN VALUE [Toc] [Back]
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate the error.
ERRORS [Toc] [Back]
On failure, t_errno is set to one of the following:
[TBADDATA] Illegal amount of data. Zero octets is not
[TBADF] The specified file descriptor does not refer to a
[TFLOW] Asynchronous mode is indicated because O_NONBLOCK
was set, but the transport provider cannot accept
the data because of flow-control restrictions.
[TLOOK] (XTI only) An asynchronous event has occurred on
this transport endpoint and requires immediate
[TNOTSUPPORT] This function is not supported by the underlying
[TOUTSTATE] (XTI only) The t_sndudata() function was issued
in the wrong sequence on the transport endpoint
referenced by the fd parameter.
[TSYSERR] A system error occurred during execution of this
function. A protocol error may not cause the
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t_sndudata() function to fail until a subsequent
call is made to access the transport endpoint
specified by the fd parameter.
[TBADADDR] The specified protocol address was in an incorrect
format or contained illegal information.
[TBADOPT] The specified options were in an incorrect format
or contained illegal information.
[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
SEE ALSO [Toc] [Back]
fcntl(2), t_alloc(3), t_open(3), t_rcvudata(3), t_rcvuderr(3).
STANDARDS CONFORMANCE [Toc] [Back]
t_sndudata(): SVID2, XPG3, XPG4
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