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t_sndudata - Send a data unit
struct t_unitdata *unitdata );
XTI Library (libxti.a)
Interfaces documented on this reference page conform to industry standards
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:
y This is a meaningful parameter.
(y) The content of the object pointed to by y is meaningful.
o This is a meaningful but optional parameter.
(o) The content of the object pointed to by o is meaningful.
n This is not a meaningful parameter.
fd 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:
struct netbuf addr
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:
unsigned int maxlen
Specifies a maximum byte length of the data buffer.
unsigned int len
Specifies the actual byte length of the data written to the
Points to the buffer location.
struct netbuf opt
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.
struct netbuf udata
Specifies the user data unit that is being sent to the remote
The unitdata->addr.maxlen, unitdata->opt.maxlen, and unitdata-
>udata.maxlen parameters are not meaningful with the t_sndudata()
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. (See t_bind().)
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
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
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
The specified options were in an incorrect format or contained illegal
This error indicates that a communication problem has been detected
between XTI and the transport provider for which there is no other
The t_sndudata() function can be called only in the T_IDLE transport
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), t_rcvudata(3)
Network Programmer's Guide
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