(TLI/XTI)

t_look(NET)

t_look -- look at the current event on a transport endpoint

Syntax

TLI syntax

cc . . . -lnsl

#include <sys/tiuser.h>

int t_look (fd)
int fd;

XTI syntax

cc . . . -lxti

#include <xti.h>

int t_look (fd)
int fd;

Description

The t_look function returns the current event on the transport endpoint specified by fd. This function enables a transport provider to notify a transport user of an asynchronous event when the user is issuing functions in synchronous mode. Certain events require immediate notification of the user and are indicated by a specific error, TLOOK, on the current or next function to be executed.

This function also enables a transport user to poll a transport endpoint periodically for asynchronous events.

Porting considerations

The XTI version of t_look never returns the event T_ERROR.

TLI does not define the events T_GODATA and T_GOEXDATA. These can be used with XTI to assist in managing flow control. A TLI application must instead resend data until it is successful. An XTI application can either call t_look or be event driven.

Return values

Upon success, t_look returns a value that indicates which of the allowable events has occurred, or returns zero if no event exists. One of the following events is returned:

T_CONNECT: connect confirmation received
T_DATA: normal data received
T_DISCONNECT: disconnect received
T_ERROR: fatal error indication; TLI only. XTI does not define this event
T_EXDATA: expedited data received
T_GODATA: sending normal data is possible again (flow control); XTI only. TLI does not define this event
T_GOEXDATA: sending expedited data is possible again (flow control); XTI only. TLI does not define this event
T_LISTEN: connection indication received
T_ORDREL: orderly release indication
T_UDERR: datagram error indication

On failure, -1 is returned, and t_errno is set to indicate the error.

Diagnostics

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

[TBADF]: The specified file descriptor does not refer to a transport endpoint.
[TSYSERR]: A system error occurred during execution of this function. errno is also set to EPROTO indicating a protocol error such as an illegal message.

Standards conformance

t_look is conformant with:

AT&T SVID Issue 3 ;
X/Open CAE Specification, Networking Services, Issue 4, 1994. ;
and Intel386 Binary Compatibility Specification, Edition 2 (iBCSe2) .