T_RCV(3N) (Networking Support Utilities) T_RCV(3N)
NAME
t_rcv - receive data or expedited data sent over a
connection
SYNOPSIS
int trcv(fd, buf, nbytes, flags)
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 t_rcv and specifies
optional flags as described below.
By default, t_rcv operates in synchronous mode and will wait
for data to arrive if none is currently available. However,
if O_NDELAY is set (via t_open or fcntl), t_rcv will execute
in asynchronous mode and will fail if no data is available.
(See TNODATA below.)
On return from the call, if T_MORE 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 t_rcv calls. Each
t_rcv with the T_MORE flag set indicates that another t_rcv
must follow immediately to get more data for the current
TSDU. The end of the TSDU is identified by the return of a
t_rcv call with the T_MORE flag not set. If the transport
provider does not support the concept of a TSDU as indicated
in the info argument on return from t_open or t_getinfo, the
T_MORE flag is not meaningful and should be ignored.
On return, the data returned is expedited data if
T_EXPEDITED is set in flags. If the number of bytes of
expedited data exceeds nbytes, t_rcv will set T_EXPEDITED
Page 1 May 1989
T_RCV(3N) (Networking Support Utilities) T_RCV(3N)
and T_MORE on return from the initial call. Subsequent
calls to retrieve the remaining ETSDU will not have
T_EXPEDITED set on return. The end of the ETSDU is
identified by the return of a t_rcv call with the T_MORE
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 (T_MORE not set) will the
remainder of the TSDU be available to the user.
On failure, t_errno may be set to one of the following:
[TBADF] The specified file descriptor does not
refer to a transport endpoint.
[TNODATA] O_NDELAY 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.
[TNOTSUPPORT] This function is not supported by the
underlying transport provider.
[TSYSERR] A system error has occurred during
execution of this function.
SEE ALSO
t_open(3N), t_snd(3N).
Network Programmer's Guide, Vol. 1.
DIAGNOSTICS
On successful completion, t_rcv returns the number of bytes
received, and it returns -1 on failure and t_errno is set to
indicate the error.
Page 2 May 1989