Name
t_open - establish a transport endpoint
Syntax
#include <tiuser.h>
int t_open(path, oflag, info)
char *path;
int oflag;
struct t_info *info;
Description
The t_open function must be called as the first step in the
initialization of a transport endpoint. This function
establishes a transport endpoint by opening a UNIX system
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/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(S)]. 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.
On failure, t_errno may be set to the following:
[TSYSERR] A system error has occurred during
execution of this function.
See Also
open(S) in the XENIX Reference.
Network Programmer's Guide.
Diagnostics
The t_open function returns a valid file descriptor on
success and -1 on failure, and t_errno is set to indicate
the error.
Standards Conformance
t_open is conformant with:
AT&T SVID Issue 2, Select Code 307-127.
(printed 6/18/89)