T_RCV(3N)

NAME
t_rcv - receive normal or expedited data sent over a connection

SYNOPSIS

int t_rcv(fd, buf, nbytes, flags)

int fd;
char *buf;
unsigned nbytes;
int *flags;

DESCRIPTION

t_rcv() 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 T_NDELAY is set (using t_open(3N) 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(3N) or t_getinfo(3N), 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 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.

RETURN VALUES

On success, t_rcv() returns the number of bytes received. On failure, it returns -1.

ERRORS

TBADF
    The specified file descriptor does not refer to a transport endpoint.

TLOOK
    An asynchronous event has occurred on this transport endpoint and requires immediate attention.

TNODATA
    T_NDELAY was set, but no data is currently available from the transport provider.

TNOTSUPPORT
    This function is not supported by the underlying transport provider.

TSYSERR
    The function failed due to a system error and set errno to indicate the error.

SEE ALSO
t_open(3N), t_snd(3N)