Technical Reference: Communications, Volume 2

t_open Subroutine for X/Open Transport Interface

Library

X/Open Transport Interface Library (libxti.a)

Syntax

#include <xti.h>
 
#include <fcntl.h>
int t_open (
    const char *name;
    int oflag;
    struct t_info *info)

The t_open subroutine must be called as the first step in the initialization of a transport endpoint. This subroutine establishes a transport endpoint by supplying a transport provider identifier that indicates a particular transport provider (for example, transport protocol) and returning a file descriptor that identifies that endpoint.

This subroutine also returns various default characteristics of the underlying transport protocol by setting fields in the t_info structure.

Parameters

name	Points to a transport provider identifier.
oflag	Identifies any open flags (as in the open exec) . The oflag parameter is constructed from O_RDWR optionally bitwise inclusive-OR-ed with O_NONBLOCK. These flags are defined by the fcntl.h header file. The file descriptor returned by the t_open subroutine is used by all subsequent subroutines to identify the particular local transport endpoint.
info	Points to a t_info structure 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 subroutines / long discon; / max amount of data allowed on / / t_snddis and t_rcvdis subroutines / 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 indicates the maximum size of a transport protocol address and a value of -2 specifies that the transport provider does not provide user access to transport protocol addresses. `options` A value greater than zero indicates the maximum number of bytes of protocol-specific options supported by the provider, 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. Note that the semantics of expedited data may be quite different for different transport providers. `connect` A value greater than zero specifies the maximum amount of data that may be associated with connection establishment subroutines and a value of -2 specifies that the transport provider does not allow data to be sent with connection establishment subroutines. `discon` A value greater than zero specifies the maximum amount of data that may be associated with the t_synddis and t_rcvdis subroutines and a value of -2 specifies that the transport provider does not allow data to be sent with the abortive release subroutines.
	`servtype` This field specifies the service type supported by the transport provider. The valid values on return are: 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. `flags` This is a bit field used to specify other information about the transport provider. If the T_SENDZERO bit is set in flags, this indicates the underlying transport provider supports the sending of zero-length TSDUs. 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 subroutine may be used to allocate these buffers. An error will result if a transport user exceeds the allowed data size on any subroutine. If the info parameter is set to a null pointer by the transport user, no protocol information is returned by the t_open subroutine.

Valid States

T_UNINIT

Return Values

Valid file descriptor	Successful completion.
-1	t_errno is set to indicate an error.

Error Codes

On failure, t_errno is set to one of the following:

TBADFLAG	An invalid flag is specified.
TBADNAME	Invalid transport provider name.
TSYSERR	A system error has occurred during execution of this subroutine.
TPROTO	This error indicates that a communication problem has been detected between the X/Open Transport Interface and the transport provider for which there is no other suitable X/Open Transport Interface (t_errno).

Related Information

The t_open subroutine.