NAME

t_rcv − receive data or expedited data sent over a connection

SYNOPSIS

int t_rcv (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 or O_NONBLOCK 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 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 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 or O_NONBLOCK 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). 

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. 

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