Networking Services Library Functions
NAME t_sndudata - send a data unit
, const struct t_unitdata *unitdata
This routine is part of the XTI
interfaces which evolved from the TLI
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;
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
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
, 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.
RETURN VALUES 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.
VALID STATES T_IDLE.
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 endpoint.
This function is not supported by the underlying transport provider.
The communications endpoint referenced by fd is not in one of the states in which a call to this function is valid.
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 function.
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.
interfaces use the header file, xti.h. TLI
interfaces should not
use this header. They should use the header:
Error Description Values
values that can be set by the XTI
interface and cannot be set by the TLI
Notes 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.
(5) for descriptions of the following attributes:
SEE ALSO 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), attributes(5)