T_SNDUDATA(3NSL) Networking Services Library Functions T_SNDUDATA(3NSL)


t_sndudata - send a data unit


#include <xti.h>

int t_sndudata(int fd, const struct t_unitdata *unitdata);


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 in connectionless-mode to send a data unit to
another transport user. The argument fd identifies the local transport
endpoint through which data will be sent, and unitdata points to a
t_unitdata structure containing the following members:

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;

In unitdata, addr specifies the protocol address of the destination user,
opt identifies 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 uses the option
values currently set for the communications endpoint.

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() 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(3NSL) or fcntl(2), t_sndudata() will
execute in asynchronous mode and will fail under such conditions. The
process can arrange to be notified of the clearance of a flow control
restriction by means of either t_look(3NSL) 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(3NSL) or
t_getinfo(3NSL), a TBADDATA error will be generated. If t_sndudata() is
called before the destination user has activated its transport endpoint
(see t_bind(3NSL)), the data unit may be discarded.

If it is not possible for the transport provider to immediately detect
the conditions that cause the errors TBADADDR and TBADOPT, these errors
will alternatively be returned by t_rcvuderr. Therefore, an application
must be prepared to receive these errors in both of these ways.

If the call is interrupted, t_sndudata() will return EINTR and the
datagram will not be sent.


Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate an error.




On failure, t_errno is set to one of the following:

The specified protocol address was in an incorrect format
or contained illegal information.

Illegal amount of data. A single send was attempted
specifying a TSDU greater than that specified in the info
argument, or a send of a zero byte TSDU is not supported
by the provider.

The specified file descriptor does not refer to a
transport endpoint.

The specified options were in an incorrect format or
contained illegal information.

O_NONBLOCK was set, but the flow control mechanism
prevented the transport provider from accepting any data
at this time.

An asynchronous event has occurred on this transport

This function is not supported by the underlying transport

The communications endpoint referenced by fd is not in
one of the states in which a call to this function is

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).

A system error has occurred during execution of this


The XTI and TLI interface definitions have common names but use different
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:


Whenever this function fails with t_error set to TFLOW, O_NONBLOCK must
have been set.

Option Buffers

The format of the options in an opt buffer is dictated by the transport
provider. Unlike the XTI interface, the TLI interface does not fix the
buffer format.


See attributes(7) for descriptions of the following attributes:

|MT Level | Safe |


fcntl(2), t_alloc(3NSL), t_bind(3NSL), t_error(3NSL), t_getinfo(3NSL),
t_look(3NSL), t_open(3NSL), t_rcvudata(3NSL), t_rcvuderr(3NSL),

May 7, 1998 T_SNDUDATA(3NSL)