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Technical Reference: Communications, Volume 2
t_open Subroutine for Transport Layer Interface
Purpose
Establishes a transport end point.
Library
Transport Layer Interface Library (libtli.a)
Syntax
#include <tiuser.h>
int t_open(path, oflag, info)
char * path;
int oflag;
struct t_info * info;
Description
The t_open subroutine must be
called as the first step in the initialization of a transport end point. This
subroutine establishes a transport end point, first, by opening a UNIX system
file that identifies a particular transport provider (that is, transport protocol)
and then returning a file descriptor that identifies that end point. For example,
opening the /dev/dlpi/tr file identifies an 802.5 data
link provider.
Parameters
path |
Points to the path name of the file to open. |
oflag |
Specifies the open routine flags. |
info |
Points to a t_info structure.
The info parameter points to a t_info structure that contains the following elements:
long addr;
long options;
long tsdu;
long etsdu;
long connect;
long discon;
long servtype;
The values of the elements
have the following meanings:
- addr
- A value greater than or equal to 0 indicates the maximum size of a
transport protocol address; a value of -1 specifies that there is no limit
on the address size; and a value of -2 specifies that the transport provider
does not provide user access to transport protocol addresses.
- options
- A value greater than or equal to 0 indicates the maximum number of
bytes of protocol-specific options supported by the provider; a value of -1
specifies that there is no limit on the option size; and a value of -2 specifies
that the transport provider does not support user-settable options.
- tsdu
- A value greater than 0 specifies the maximum size of a transport service
data unit (TSDU); a value of 0 specifies that the transport provider does
not support the concept of TSDU, although it does support the sending of a
data stream having no logical boundaries preserved across a connection; a
value of -1 specifies that there is no limit on the size of a TSDU; and a
value of -2 specifies that the transfer of normal data is not supported by
the transport provider.
- etsdu
- A value greater than 0 specifies the maximum size of a expedited transport
service data unit (ETSDU); a value of 0 specifies that the transport provider
does not support the concept of ETSDU, although it does support the sending
of an expedited data stream having no logical boundaries preserved across
a connection; a value of -1 specifies that there is no limit on the size of
an ETSDU; and a value of -2 specifies that the transfer of expedited data
is not supported by the transport provider.
- connect
- A value greater than or equal to 0 specifies the maximum amount of
data that may be associated with connection establishment functions; a value
of -1 specifies that there is no limit on the amount of data sent during connection
establishment; and a value of -2 specifies that the transport provider does
not allow data to be sent with connection establishment functions.
- discon
- A value greater than or equal to 0 specifies the maximum amount of
data that may be associated with the t_snddis and t_rcvdis
functions; a value of -1 specifies that there is no limit on the amount of
data sent with these abortive release functions; and a value of -2 specifies
that the transport provider does not allow data to be sent with the abortive
release functions.
- servtype
- This field specifies the service type supported by the transport provider,
as described in the Return Values section.
|
|
If a transport user is concerned with protocol
independence, these sizes may be accessed to determine how large the buffers
must be to hold each piece of information. Alternatively, the t_alloc subroutine can be used to allocate these buffers.
An error results if a transport user exceeds the allowed data size on any
function. |
Return Values
On successful completion, the t_open subroutine returns a valid file descriptor. Otherwise, it returns a
value of -1, and the t_errno variable is set to indicate
the error.
The servtype field of
the info parameter can specify one of the following
values on return:
Value |
Description |
T_COTS |
The transport provider supports a connection-mode service but does
not support the optional orderly release facility. |
T_COTS_ORD |
The transport provider supports a connection-mode service with the
optional orderly release facility. |
T_CLTS |
The transport provider supports a connectionless-mode service. For
this service type, the t_open subroutine returns -2
for the values in the etsdu, connect, and discon fields. |
A single transport end point can support only one
of the above services at one time.
If the info parameter is set
to null by the transport user, no protocol information is returned by the t_open subroutine.
Error Codes
If unsuccessful, the t_errno
variable is set to the following:
Value |
Description |
TSYSERR |
A system error has occurred during the startup of this function. |
Related Information
The open subroutine, t_close
subroutine.
List of Streams Programming
References and STREAMS Overview in AIX 5L Version 5.2 Communications Programming Concepts.
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