t_open(3N) UNIX System V(Networking Support Utilities) t_open(3N)
NAME
topen - establish a transport endpoint
SYNOPSIS
#include <tiuser.h>
#include <fcntl.h>
int topen (char path, int oflag, struct tinfo *info);
DESCRIPTION
topen 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 (that
is, transport protocol) and returning a file descriptor that identifies
that endpoint. For example, opening the file /dev/isocots 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 ONDELAY
or ONONBLOCK OR-ed with ORDWR. These flags are defined in the header
file <fcntl.h>. topen returns a file descriptor that will be used by
all subsequent functions to identify the particular local transport
endpoint.
topen also returns various default characteristics of the underlying
transport protocol by setting fields in the tinfo structure. The tinfo
argument points to a tinfo structure that contains the following
members:
long addr;/* maximum size of the transport protocol address */
long options;/* maximum number of bytes of protocol-specific options */
long tsdu;/* maximum size of a transport service data unit (TSDU) */
long etsdu;/* maximum size of an expedited transport service data unit (ETSDU) */
long connect;/* maximum amount of data allowed on connection establishment
functions */
long discon;/* maximum amount of data allowed on tsnddis and trcvdis
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
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t_open(3N) UNIX System V(Networking Support Utilities) t_open(3N)
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 tsnddis and
trcvdis 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 talloc 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:
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t_open(3N) UNIX System V(Networking Support Utilities) t_open(3N)
TCOTS The transport provider supports a connection-mode service
but does not support the optional orderly release facility.
TCOTSORD The transport provider supports a connection-mode service
with the optional orderly release facility.
TCLTS The transport provider supports a connectionless-mode
service. For this service type, topen 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 topen.
On failure, terrno may be set to the following:
TSYSERR A system error has occurred during execution of this
function.
TBADFLAG An invalid flag is specified.
DIAGNOSTICS
topen returns a valid file descriptor on success and -1 on failure and
terrno is set to indicate the error.
NOTES
If topen is used on a non-TLI-conforming STREAMS device, unpredictable
events may occur.
SEE ALSO
open(2)
Programmer's Guide: Networking Interfaces
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