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Communications Technical Reference, Volume 2
t_look Subroutine for X/Open Transport Interface
Purpose
Look at the current event on a transport endpoint.
Library
X/Open Transport Interface Library (libxti.a)
Syntax
#include <xti.h>
int t_look (fd)
int fd;
Description
The t_look subroutine returns the current event on the transport endpoint specified by the fd parameter. This subroutine enables a transport provider to notify a transport user of an asynchronous event when the user is calling subroutines in synchronous mode. Certain events require immediate notification of the user and are indicated by a specific error, TLOOK, on the current or next subroutine to be executed.
Details on events which cause subroutines to fail, T_LOOK, may be found in Section 4.6, Events and TLOOK Error Indication.
This subroutine also enables a transport user to poll a transport endpoint periodically for asynchronous events.
Parameter
fd |
Specifies the transport endpoint. |
Valid States
ALL - apart from T_UNINIT.
Return Values
Upon success, the t_look subroutine 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_LISTEN |
Connection indication received. |
T_CONNECT |
Connect confirmation received. |
T_DATA |
Normal data received. |
T_EXDATA |
Expedited data received. |
T_DISCONNECT |
Disconnect received. |
T_UDERR |
Datagram error indication. |
T_ORDREL |
Orderly release indication. |
T_GODATA |
Flow control restrictions on normal data flow that led to a TFLOW error have been lifted. Normal data may be sent again. |
T_GOEXDATA |
Flow control restrictions on expedited data flow that led to a TFLOW error have been lifted. Expedited data may be sent again. |
On failure, -1 is returned and t_errno is set to indicate the error.
Error Codes
On failure, t_errno is set to one of the following:
TBADF |
The specified file descriptor does not refer to a transport endpoint. |
TSYSERR |
A system error has occurred during execution of this subroutine. |
TPROTO |
This error indicates that a communication problem has been detected between the X/Open Transport Interface and the transport provider for which there is no other suitable X/Open Transport Interface (t_errno). |
Implementation Specifics
Additional functionality is provided through the Event Management (EM) interface.
Related Information
The t_open subroutine, t_snd subroutine, t_sndudata subroutine.
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