t_snd(3N) (Networking Support Utilities) t_snd(3N)
NAME
tsnd - send data or expedited data over a connection
SYNOPSIS
#include <tiuser.h>
int tsnd (int fd, char *buf, unsigned nbytes, int flags);
DESCRIPTION
This function is used to send either normal or expedited data. fd
identifies the local transport endpoint over which data should be
sent, buf points to the user data, nbytes specifies the number of
bytes of user data to be sent, and flags specifies any optional flags
described below.
By default, tsnd 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
ONDELAY or ONONBLOCK is set (via topen or fcntl), tsnd will
execute in asynchronous mode, and will fail immediately if there are
flow control restrictions.
Even when there are no flow control restrictions, tsnd will wait if
STREAMS internal resources are not available, regardless of the state
of ONDELAY or ONONBLOCK.
On successful completion, tsnd returns the number of bytes accepted
by the transport provider. Normally this will equal the number of
bytes specified in nbytes. However, if ONDELAY or ONONBLOCK is
set, it is possible that only part of the data will be accepted by
the transport provider. In this case, tsnd will set TMORE for the
data that was sent (see below) and will return a value less than
nbytes. If nbytes is zero and sending of zero bytes is not supported
by the underlying transport provider, tsnd() will return -1 with
terrno set to TBADDATA. A return value of zero indicates that the
request to send a zero-length data message was sent to the provider.
If TEXPEDITED is set in flags, the data will be sent as expedited
data, and will be subject to the interpretations of the transport
provider.
If TMORE is set in flags, or is set as described above, an
indication is sent to the transport provider that the transport
service data unit (TSDU) or expedited transport service data unit
(ETSDU) is being sent through multiple tsnd calls. Each tsnd with
the TMORE flag set indicates that another tsnd will follow with
more data for the current TSDU. The end of the TSDU (or ETSDU) is
identified by a tsnd call with the TMORE flag not set. Use of
TMORE enables a user to break up large logical data units without
losing the boundaries of those units at the other end of the
connection. The flag implies nothing about how the data is packaged
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t_snd(3N) (Networking Support Utilities) t_snd(3N)
for transfer below the transport interface. If the transport
provider does not support the concept of a TSDU as indicated in the
info argument on return from topen or tgetinfo, the TMORE flag is
not meaningful and should be ignored.
The size of each TSDU or ETSDU must not exceed the limits of the
transport provider as returned by topen or tgetinfo. If the size
is exceeded, a TSYSERR with system error EPROTO will occur. However,
the tsnd may not fail because EPROTO errors may not be reported
immediately. In this case, a subsequent call that accesses the
transport endpoint will fail with the associated TSYSERR.
If tsnd is issued from the TIDLE state, the provider may silently
discard the data. If tsnd is issued from any state other than
TDATAXFER, TINREL or TIDLE, the provider will generate a TSYSERR
with system error EPROTO (which may be reported in the manner
described above).
On failure, terrno may be set to one of the following:
[TBADF] The specified file descriptor does not refer to a
transport endpoint.
[TFLOW] ONDELAY or ONONBLOCK was set, but the flow
control mechanism prevented the transport
provider from accepting data at this time.
[TNOTSUPPORT] This function is not supported by the underlying
transport provider.
[TSYSERR] A system error [see intro(2)] has been detected
during execution of this function.
[TBADDATA] nbytes is zero and sending zero bytes is not
supported by the transport provider.
SEE ALSO
topen(3N), trcv(3N).
Programmer's Guide: Networking Interfaces.
DIAGNOSTICS
On successful completion, tsnd returns the number of bytes accepted
by the transport provider, and it returns -1 on failure and terrno
is set to indicate the error.
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