t_rcv(3N)

NAME

t_rcv − receive data or expedited data sent over a connection

SYNOPSIS

cc [ flag ... ] file ... −lnsl [ library ... ]

int t_rcv(int fildes, char ∗buf, unsigned nbytes, int ∗flags);

DESCRIPTION

This function receives either normal or expedited data. fildes 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 or O_NONBLOCK is set (using 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 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 and T_MORE on return from the initial call. Subsequent calls to retrieve the remaining ETSDU will 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 ETSDU 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 successful completion, t_rcv() returns the number of bytes received. On failure t_rcv() returns −1, t_errno is set to indicate the error, and possibly errno is set.

ERRORS

On failure, t_errno will be set to one of the following:

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 O_NDELAY or O_NONBLOCK was set, but no data is currently available from the transport provider.

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

TSYSERR A system error has occurred during execution of this function, errno will be set to the specific error.

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