NAME

t_open − establish a transport endpoint

SYNOPSIS

#include <tiuser.h>

#include <fcntl.h>

int t_open (path, oflag, info)
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 (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 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. 

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 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. 

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. 

[TBADNAME] The path parameter does not specify a valid transport provider. 

[TBADFLAG] An invalid flag is specified. 

SEE ALSO

open(2).  CX/UX Networking Reference Manual

DIAGNOSTICS

Upon successful completion, a valid file descriptor is returned.  Otherwise, a value of -1 is returned and t_errno is set to indicate the error. 

CX/UX Networking