T_OPEN(3N) SysV T_OPEN(3N)
NAME
t_open - establish a transport endpoint
SYNOPSIS
#include <tiuser.h>
int t_open(path, oflag, info)
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 device that identifies a particular transport provider (that is
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 pathname of the file to open, and oflag identifies any
open flags (as in open(2)). 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 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.
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 NULL by the transport user, no protocol information is
returned by t_open.
DIAGNOSTICS
t_open returns a valid file descriptor on success and -1 on failure and
t_errno is set to indicate the error.
ERRORS
On failure, t_errno may be set to the following:
[TSYSERR] A system error has occurred during execution of this
function.
SEE ALSO
open(2)
Programming with the SysV Transport Interface