t_rcvudata(3)

NAME

t_rcvudata − receive a data unit

SYNOPSIS

#include <xti.h> (for XTI)

#include <tiuser.h> (for TLI)

int t_rcvudata (fd, unitdata, flags)
inf fd;
struct t_unitdata *unitdata;
int *flags;

DESCRIPTION

This function is used in connectionless-mode to receive a data unit from a remote transport provider user. The argument fd identifies the local transport endpoint through which data will be received, unitdata holds information associated with the received data unit, and flags is set on return to indicate that the complete data unit was not received. The argument unitdata points to a t_unitdata structure containing the following members:

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;

The type netbuf structure is defined in the <xti.h> or <tiuser.h> header file. This structure, which is used to define buffer parameters, has the following members:

unsigned int maxlen maximum byte length of the data buffer

unsigned int len actual byte length of data written to buffer

char *buf points to buffer location

The maxlen field of addr, opt and udata must be set before calling this function to indicate the maximum size of the buffer for each.

On return from this call, addr specifies the protocol address of the sending user, opt identifies protocol-specific options that were associated with this data unit, and udata specifies the user data that was received.

By default, t_rcvudata() executes in the synchronous operating mode. The t_rcvudata() function waits for data to arrive at the transport endpoint specified by fd before returning control to the transport user who called this function. However, when the transport endpoint, specified by the fd parameter, has the O_NONBLOCK or O_NDELAY option set by t_open(3) or fcntl(2) function, the t_rcvudata() function executes in asynchronous mode. In asynchronous mode, when a data unit is unavailable, control is immediately returned to the caller.

If the buffer defined in the udata field of unitdata is not large enough to hold the current data unit, the buffer will be filled and T_MORE will be set in flags on return to indicate that another t_rcvudata() should be called to retrieve the rest of the data unit. Subsequent calls to t_rcvudata() will return zero for the length of the address and options until the full data unit has been received.

ERRORS

On failure, t_errno is set to one of the following:

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

[TNODATA] O_NONBLOCK or O_NDELAY was set, but no data units are currently available from the transport provider.

[TBUFOVFLW] The number of bytes allocated for the incoming protocol address or protocol options is not sufficient to store the information. The unit data information normally returned in unitdata is discarded.

[TLOOK] An asynchronous event has occurred on this transport endpoint required immediate attention.

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

[TOUTSTATE] (XTI only) The function was issued in the wrong sequence on the transport endpoint referenced by fd.

[TSYSERR] A system error occurred during execution of this function.

RETURN VALUE

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and t_errno is set to indicate the error.

NOTE

For portability purposes, it is recommended that O_NONBLOCK be used instead of O_NDELAY.

In HP-UX 9.0, XTI (X/Open Transport Interface) supports only OSI as a transport provider, and is available only as part of the OSI Transport Services 9000 product. Users of this product can access XTI versions of the t_* routines by linking with /usr/lib/libxti.a. For more information on XTI, see "HP-UX/9000 XTI Programmer’s Guide".

In HP-UX 9.0, TLI (Transport Layer Interface) supports any transport provider which is compliant with TPI (Transport Provider Interface). TLI is available only as part of the STREAMS product. Users of this product can access TLI versions of the t_* routines by linking with /usr/lib/libnsl_s.a. For more information on TLI, see the TLI section of "STREAMS/UX for HP 9000 Reference Manual".

Museum

Related Articles