NAME

t_open − establish a transport endpoint

SYNOPSIS

#include <tiuser.h>

#include <fcntl.h>

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

DESCRIPTION

t_open 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. 

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 OR -ed with O_RDWR.  These flags are defined in the header file <fcntl.h>.  t_open returns a file descriptor that will be used by all subsequent functions to identify the particular local transport endpoint. 

t_open also returns various default characteristics of the underlying transport protocol by setting fields in the t_info structure.  The t_info argument points to a t_info structure that contains the following members:

long addr;/∗ maximum size of the transport protocol address ∗/
long options;/∗ maximum number of bytes of protocol-specific options ∗/
long tsdu;/∗ maximum size of a transport service data unit (TSDU) ∗/
long etsdu;/∗ maximum size of an expedited transport service data unit (ETSDU) ∗/
long connect;/∗ maximum amount of data allowed on connection establishment
    functions ∗/
long discon;/∗ maximum 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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 the size of the field will be set to the default of 1024 bytes by t_alloc(); 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. 

TBADFLAG An invalid flag is specified. 

DIAGNOSTICS

t_open returns a valid file descriptor on success and −1 on failure and t_errno is set to indicate the error. 

NOTES

If t_open is used on a non-TLI-conforming STREAMS device, unpredictable events may occur. 

SEE ALSO

open(2). 

  —  Networking Support Utilities