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
| Item |
Description |
|---|
| 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. |