TOPEN(3N-SVR4) RISC/os Reference Manual TOPEN(3N-SVR4)
NAME
t_open - 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 initializa-
tion 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 ORO_RDWR. These
flags are defined in the header file <fcntl.h>. t_open
returns a file descriptor that will be used by all subse-
quent 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 indi-
cates 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 indi-
cates the maximum number of bytes of
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TOPEN(3N-SVR4) RISC/os Reference Manual TOPEN(3N-SVR4)
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 max-
imum size of a transport service data unit
(TSDU); a value of zero specifies that the
transport provider does not support the con-
cept of TSDU, although it does support the
sending of a data stream with no logical boun-
daries 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 sup-
ported by the transport provider.
etsdu A value greater than zero specifies the max-
imum 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 con-
nection; 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 pro-
vider.
connect A value greater than or equal to zero speci-
fies the maximum amount of data that may be
associated with connection establishment func-
tions; 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 estab-
lishment functions.
discon A value greater than or equal to zero speci-
fies 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 abor-
tive release functions.
servtype This field specifies the service type
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TOPEN(3N-SVR4) RISC/os Reference Manual TOPEN(3N-SVR4)
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. Alterna-
tively, 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, topen will return -2 for etsdu, con-
nect, 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 topen.
On failure, t_errno may be set to the following:
[TSYSERR] A system error has occurred during exe-
cution of this function.
[TBADFLAG] An invalid flag is specified.
SEE ALSO
open(2).
DIAGNOSTICS
topen returns a valid file descriptor on success and -1 on
failure and t_errno is set to indicate the error.
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