t_rcv(3N) UNIX System V(Networking Support Utilities) t_rcv(3N)
NAME
trcv - receive data or expedited data sent over a connection
SYNOPSIS
int trcv (int fd, char *buf, unsigned nbytes, int *flags);
DESCRIPTION
This function receives either normal or expedited data. fd identifies
the local transport endpoint through which data will arrive, buf points
to a receive buffer where user data will be placed, and nbytes specifies
the size of the receive buffer. flags may be set on return from trcv
and specifies optional flags as described below.
By default, trcv operates in synchronous mode and will wait for data to
arrive if none is currently available. However, if ONDELAY or
ONONBLOCK is set (via topen or fcntl), trcv will execute in
asynchronous mode and will fail if no data is available. (See TNODATA
below.)
On return from the call, if TMORE is set in flags, this indicates that
there is more data and the current transport service data unit (TSDU) or
expedited transport service data unit (ETSDU) must be received in
multiple trcv calls. Each trcv with the TMORE flag set indicates that
another trcv must follow to get more data for the current TSDU. The end
of the TSDU is identified by the return of a trcv call with the TMORE
flag not set. 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.
On return, the data returned is expedited data if TEXPEDITED is set in
flags. If the number of bytes of expedited data exceeds nbytes, trcv
will set TEXPEDITED and TMORE on return from the initial call.
Subsequent calls to retrieve the remaining ETSDU will have TEXPEDITED
set on return. The end of the ETSDU is identified by the return of a
trcv call with the TMORE flag not set.
If expedited data arrives after part of a TSDU has been retrieved,
receipt of the remainder of the TSDU will be suspended until the ETSDU
has been processed. Only after the full ETSDU has been retrieved (TMORE
not set) will the remainder of the TSDU be available to the user.
On failure, terrno may be set to one of the following:
TBADF The specified file descriptor does not refer to a
transport endpoint.
TNODATA ONDELAY or ONONBLOCK was set, but no data is
currently available from the transport provider.
TLOOK An asynchronous event has occurred on this transport
endpoint and requires immediate attention.
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t_rcv(3N) UNIX System V(Networking Support Utilities) t_rcv(3N)
TNOTSUPPORT This function is not supported by the underlying
transport provider.
TSYSERR A system error has occurred during execution of this
function.
SEE ALSO
topen(3N), tsnd(3N)
Programmer's Guide: Networking Interfaces
DIAGNOSTICS
On successful completion, trcv returns the number of bytes received, and
it returns -1 on failure and terrno is set to indicate the error.
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