t_open(3N)

NAME

t_open − establish a transport endpoint

SYNOPSIS

cc [ flag ... ] file ... −lnsl [ library ... ]

#include <xti.h>
#include <fcntl.h>

int t_open(const char ∗name, int oflag, struct t_info ∗info);

DESCRIPTION

This routine is part of the XTI interfaces which evolved from the TLI interfaces. XTI represents the future evolution of these interfaces. However, TLI interfaces are supported for compatibility. When using a TLI routine that has the same name as an XTI routine, a different header file, tiuser.h , must be used. Refer to the section, TLI COMPATIBILITY , for a description of differences between the two interfaces.

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 taking a supplied protocol identifier, name, and by returning a file descriptor that identifies that endpoint.

The argument name points to a transport provider identifier and oflag identifies any open flags (as in open(2)). The argument oflag can be specified using O_RDWR or using a bitwise inclusive- OR operation with the required value O_RDWR and the optional value O_NONBLOCK . These flags are defined in the header, fcntl.h. 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 a t_info structure.

A t_info 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∗/
long flags;/∗ other info about the transport provider∗/

The values of the fields have the following meanings:

addr A value greater than zero (> T_NULL ) indicates the maximum size of a transport protocol address and a value of −2 ( T_INVALID ) specifies that the transport provider does not provide user access to transport protocol addresses.

options A value greater than zero (> T_NULL ) indicates the maximum number of bytes of protocol-specific options supported by the provider, and a value of −2( T_INVALID ) specifies that the transport provider does not support user-selectable options.

tsdu A value greater than zero (> T_NULL ) specifies the maximum size of a transport service data unit ( TSDU ); a value of zero ( T_NULL ) specifies that the transport provider does not support the concept of a TSDU value, although it does support the sending of a data stream with no logical boundaries preserved across a connection; a value of −1 ( T_INFINITE ) specifies that there is no limit to the size of a TSDU ; and a value of −2 ( T_INVALID ) specifies that the transfer of normal data is not supported by the transport provider.

etsdu A value greater than zero (> T_NULL ) specifies the maximum size of an expedited transport service data unit ( ETSDU ); a value of zero ( T_NULL ) 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 ( T_INFINITE ) specifies that there is no limit on the size of an ETSDU ; and a value of −2 ( T_INVALID ) specifies that the transfer of expedited data is not supported by the transport provider. Note that the semantics of expedited data may be quite different for different transport providers.

connect A value greater than zero (> T_NULL ) specifies the maximum amount of data that may be associated with connection establishment functions, and a value of −2 ( T_INVALID ) specifies that the transport provider does not allow data to be sent with connection establishment functions.

discon a value greater than zero (> T_NULL ) specifies the maximum amount of data that may be associated with the t_snddis() and t_rcvdis() functions, and a value of −2 ( T_INVALID ) 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.

flags This is a bit field used to specify other information about the communications provider. If the T_SENDZERO bit is set in flags, this indicates the underlying transport provider supports the sending of zero-length TSDU s.

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(3N) 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 info specifies 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 ( T_INVALID ) 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 a null pointer by the transport user, no protocol information is returned by t_open().

VALID STATES

The only legitimate state (see t_getstate(3N)) for a call to this routine is the conceptual state T_UNINIT .

RETURN VALUES

t_open() returns:

A Valid File Descriptor On success.

−1 On failure.

On failure, t_errno is set to indicate the error, and possibly errno is set.

ERRORS

On failure, t_errno is set to the following:

TBADFLAG An invalid flag is specified.

TBADNAME Invalid transport provider name.

TPROTO This error indicates that a communication problem has been detected between XTI and the transport provider for which there is no other suitable XTI t_errno value.

TSYSERR A system error has occurred during execution of this function, errno will be set to the specific error.

TLI COMPATIBILITY

The XTI and TLI interface definitions have common names but use different header files. This, and other semantic differences between the two interfaces are described in the subsections below.

Interface Header

The XTI interfaces use the header file, xti.h . TLI interfaces should not use this header. They should use the header:

#include <tiuser.h>

Error Description Values

The t_errno values that can be set by the XTI interface and cannot be set by the TLI interface are:

TPROTO

TBADNAME

Notes

For TLI , the t_info structure referenced by info lacks the following structure member:

long flags;
/∗ other info about the transport provider ∗/

This member was added to struct t_info in the XTI interfaces.

When a value of −1 is observed as the return value in various t_info structure members, it signifies that the transport provider can handle an infinite length buffer for a corresponding attribute, such as address data, option data, TSDU (octet size), ETSDU (octet size), connection data, and disconnection data. The corresponding structure members are addr, options, tsdu, estdu, connect, and discon, respectively.

For more information refer to the Transport Interfaces Programming Guide.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT-Level	MT-Safe

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