t_rcv(3N) DG/UX 5.4.2 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
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t_rcv(3N) DG/UX 5.4.2 t_rcv(3N)
attention.
[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).
UNIX System V Network Programmer's Guide.
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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