t_open(3) CLIX t_open(3)
NAME
t_open - Establishes a transport endpoint
LIBRARY
Transport Layer Interface (TLI) Library (libnsl_s.a)
SYNOPSIS
#include <tiuser.h>
int t_open(
char *path ,
int oflag ,
struct t_info *info );
PARAMETERS
path A pointer to the pathname of the file to open
oflag An integer representing a mode flag
info A pointer to a t_info structure
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 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.
The path parameter points to the pathname of the file to open, and oflag
identifies any open flags (as in open()). The t_open() function 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 structure which has 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 */
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t_open(3) CLIX t_open(3)
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.
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t_open(3) CLIX t_open(3)
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().
RETURN VALUES
The t_open() function 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.
RELATED INFORMATION
Functions: open(3)
AT&T UNIX System V Network Programmer's Guide
2/94 - Intergraph Corporation 3