t_open(3N) (Networking Support Utilities) t_open(3N)
NAME
t_open - establish a transport endpoint
SYNOPSIS
#include <tiuser.h>
#include <fcntl.h>
int t_open (char path, int oflag, struct t_info *info);
DESCRIPTION
t_open must be called as the first step in the initialization of a
transport endpoint. This function establishes a transport endpoint
by opening a UNIX file that identifies a particular transport
provider (i.e., transport protocol) and returning a file descriptor
that identifies that endpoint. For example, opening the file
/dev/iso_cots identifies an OSI connection-oriented transport layer
protocol as the transport provider.
path points to the path name of the file to open, and oflag
identifies any open flags [as in open(2)]. oflag may be constructed
from O_NDELAY or O_NONBLOCK OR-ed with O_RDWR. These flags are
defined in the header file <fcntl.h>. t_open returns a file
descriptor that will be used by all subsequent functions to identify
the particular local transport endpoint.
This function also returns various default characteristics of the
underlying transport protocol by setting fields in the t_info
structure. This argument points to a t_info which contains the
following members:
long addr;/* max size of the transport protocol address */
long options;/* max number of bytes of protocol-specific options */
long tsdu;/* max size of a transport service data unit (TSDU) */
long etsdu;/* max size of an expedited transport service data unit (ETSDU) */
long connect;/* max amount of data allowed on connection establishment functions */
long discon;/* max amount of data allowed on t_snddis and t_rcvdis functions */
long servtype;/* service type supported by the transport provider */
The values of the fields have the following meanings:
addr A value greater than or equal to zero 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 zero indicates the
maximum number of bytes of protocol-specific options
supported by the provider; a value of -1 specifies that
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t_open(3N) (Networking Support Utilities) t_open(3N)
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 zero specifies the maximum size of
a transport service data unit (TSDU); a value of zero
specifies that the transport provider does not support
the concept of TSDU, although it does support the
sending of a data stream with 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 zero specifies the maximum size of
an expedited transport service data unit (ETSDU); a
value of zero specifies that the transport provider
does not support the concept of ETSDU, although it does
support the sending of an expedited data stream with 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 zero 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 zero 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 below.
If a transport user is concerned with protocol independence, the
above sizes may be accessed to determine how large the buffers must
be to hold each piece of information. Alternatively, the t_alloc
function may be used to allocate these buffers. An error will result
if a transport user exceeds the allowed data size on any function.
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t_open(3N) (Networking Support Utilities) t_open(3N)
The servtype field of info may specify one of the following values on
return:
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, t_open will return -2
for etsdu, connect, and discon.
A single transport endpoint may support only one of the above
services at one time.
If info is set to ULL by the transport user, no protocol information
is returned by t_open.
On failure, t_errno may be set to the following:
[TSYSERR] A system error has occurred during execution of
this function.
[TBADFLAG] An invalid flag is specified.
SEE ALSO
open(2).
Programmer's Guide: Networking Interfaces.
DIAGNOSTICS
t_open returns a valid file descriptor on success and -1 on failure
and t_errno is set to indicate the error.
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