t_sndudata - Send a data unit
struct t_unitdata *unitdata );
XTI Library (libxti.a)
Interfaces documented on this reference page conform to
industry standards as follows:
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
The following table summarizes the relevance of input and
output parameters before and after t_sndudata() is called:
Parameters Before Call After Call
fd y n
unitdata->addr.maxlen n n
unitdata->addr.len y n
unitdata->addr.buf y(y) n
unitdata->opt.maxlen n n
unitdata->opt.len y n
unitdata->opt.buf o(o) n
unitdata->udata.maxlen n n
unitdata->udata.len y n
unitdata->udata.buf y(y) n
Notes to Table: This is a meaningful parameter. The content
of the object pointed to by y is meaningful. This is
a meaningful but optional parameter. The content of the
object pointed to by o is meaningful. This is not a meaningful
parameter. Specifies a file descriptor returned by
the t_open() function that identifies the transport endpoint
through which data is sent. 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: References a buffer for protocol address information
of the remote transport user. The type netbuf structure
referenced by this member is defined in the xti.h
include file and has the following members: Specifies a
maximum byte length of the data buffer. Specifies the
actual byte length of the data written to the buffer.
Points to the buffer location. Identifies options that
the user wants associated with this request. 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.
Specifies the user data unit that is being sent to the
remote transport user.
The unitdata->addr.maxlen, unitdata->opt.maxlen,
and unitdata->udata.maxlen parameters are not meaningful
with the t_sndudata() function.
If the udata.len parameter is specified as 0
(zero), and the underlying transport service does
not support the sending of 0 (zero) octets, t_errno
is set to [TBADDATA] and -1 is returned.
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 is generated. If t_sndudata() is called
before the destination user has activated its
transport endpoint, the data unit may be discarded.
The t_sndudata() function is an XTI connectionless service
function that is used to send a data unit to a remote
transport user. By default, t_sndudata() executes in the
synchronous operating mode. The t_sndudata() function
waits for the transport provider to accept the data before
returning control to the calling transport user.
When the transport endpoint specified by the fd parameter
has been previously opened with the O_NONBLOCK option set
in the t_open() or fcntl() functions, the t_sndudata()
function executes in asynchronous mode. In asynchronous
mode, when a data unit is not accepted control is immediately
returned to the caller. The t_look() function or the
EM interface can be used to determine when flow control
restrictions have been lifted.
If the t_sndudata() function fails, t_errno may be set to
one of the following values: Illegal amount of data. Zero
octets is not supported. File descriptor fd is not a
valid transport endpoint. Asynchronous mode is indicated
because O_NONBLOCK was set, but the transport provider
cannot accept the data because of flow-control restrictions.
An asynchronous event has occurred on this transport
endpoint and requires immediate attention. This
function is not supported by the underlying transport
provider. The t_sndudata() function was issued in the
wrong sequence on the transport endpoint referenced by the
fd parameter. A system error occurred during execution of
this function. A protocol error may not cause the t_sndudata()
function to fail until a subsequent call is made to
access the transport endpoint specified by the fd parameter.
The specified protocol address was in an incorrect
format or contained illegal information. The specified
options were in an incorrect format or contained illegal
information. This error indicates that a communication
problem has been detected between XTI and the transport
provider for which there is no other suitable
The t_sndudata() function can be called only in the T_IDLE
transport provider state.
Upon successful completion, a value of 0 (zero) is
returned. Otherwise, a value of -1 is returned and t_errno
is set to indicate the error.
Functions: fcntl(2), t_alloc(3), t_open(3), t_rcvuderr(3),
Network Programmer's Guide
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