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


cc [options] file -lnsl
#include <xti.h>

int t_rcv(int fd, char *buf, unsigned int nbytes, int *flags);


This function is a TLI/XTI connection-mode data transfer routine which retrieves normal or expedited data received over a connection. The messages sent to the transport user may be 0-length.

By default, t_rcv operates in synchronous mode and will wait for data to arrive if none is currently available. However, if 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 from the call, if T_EXPEDITED is set in flags the data returned is expedited data. 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.


the file descriptor for the transport endpoint through which data will arrive.

points to the receive buffer where user data will be placed.

specifies the size of the receive buffer.

specifies optional flags on return.

State transitions

On entry, T_DATAXFER or T_OUTREL; unchanged (successful) on exit.


X/Open® Transport Interface Library (shared object)

Network Services Library (shared object)


t_rcv is applicable only for connection-mode transport services.

In synchronous mode, t_look may alternatively be used to notify the transport user that normal or expedited data has been received or that flow control restrictions have been lifted. Additional functionality is provided by the Event Management Interface.

Return values

On successful completion, t_rcv returns the number of bytes received. On failure, it returns -1 and t_errno is set to indicate the error.


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

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

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

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

This function is not supported by the underlying transport provider.

A system error has occurred during execution of this function.

The function was issued in the wrong sequence on the transport endpoint referenced by fd.

A communication problem has been detected with the transport provider and there is no other value of t_errno to describe the error condition.


fcntl(S), intro(S), t_getinfo(NET), t_look(NET), t_open(NET), t_snd(NET)
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 - 01 June 2005