Tribblix: manual page: t

T_CONNECT(3NSL) Networking Services Library Functions T_CONNECT(3NSL)

NAME

t_connect - establish a connection with another transport user

SYNOPSIS

#include <xti.h>

int t_connect(int fd, const struct t_call *sndcall,
struct t_call *rcvcall);

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, the tiuser.h
header file must be used. Refer to the TLI COMPATIBILITY section
for a description of differences between the two interfaces. This
function enables a transport user to request a connection to the
specified destination transport user.

This function can only be issued in the T_IDLE state. The parameter
fd identifies the local transport endpoint where communication will
be established, while sndcall and rcvcall point to a t_call structure
which contains the following members:

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
int sequence;

The parameter sndcall specifies information needed by the transport
provider to establish a connection and rcvcall specifies information
that is associated with the newly established connection.

In sndcall, addr specifies the protocol address of the destination
transport user, opt presents any protocol-specific information that
might be needed by the transport provider, udata points to optional
user data that may be passed to the destination transport user during
connection establishment, and sequence has no meaning for this
function.

On return, in rcvcall, addr contains the protocol address associated
with the responding transport endpoint, opt represents any protocol-
specific information associated with the connection, udata points to
optional user data that may be returned by the destination transport
user during connection establishment, and sequence has no meaning for
this function.

The opt argument permits users to define the options that may be
passed to the transport provider. The user may choose not to
negotiate protocol options by setting the len field of opt to zero.
In this case, the provider uses the option values currently set for
the communications endpoint.

If used, sndcall->opt.buf must point to a buffer with the
corresponding options, and sndcall->opt.len must specify its length.
The maxlen and buf fields of the netbuf structure pointed by
rcvcall->addr and rcvcall->opt must be set before the call.

The udata argument enables the caller to pass user data to the
destination transport user and receive user data from the destination
user during connection establishment. However, the amount of user
data must not exceed the limits supported by the transport provider
as returned in the connect field of the info argument of t_open(3NSL)
or t_getinfo(3NSL). If the len of udata is zero in sndcall, no data
will be sent to the destination transport user.

On return, the addr, opt and udata fields of rcvcall will be updated
to reflect values associated with the connection. Thus, the maxlen
field of each argument must be set before issuing this function to
indicate the maximum size of the buffer for each. However, maxlen can
be set to zero, in which case no information to this specific
argument is given to the user on the return from t_connect(). If
maxlen is greater than zero and less than the length of the value,
t_connect() fails with t_errno set to TBUFOVFLW. If rcvcall is set
to NULL, no information at all is returned.

By default, t_connect() executes in synchronous mode, and will wait
for the destination user's response before returning control to the
local user. A successful return (that is, return value of zero)
indicates that the requested connection has been established.
However, if O_NONBLOCK is set by means of t_open(3NSL) or fcntl(2),
t_connect() executes in asynchronous mode. In this case, the call
will not wait for the remote user's response, but will return control
immediately to the local user and return -1 with t_errno set to
TNODATA to indicate that the connection has not yet been established.
In this way, the function simply initiates the connection
establishment procedure by sending a connection request to the
destination transport user. The t_rcvconnect(3NSL) function is used
in conjunction with t_connect() to determine the status of the
requested connection.

When a synchronous t_connect() call is interrupted by the arrival of
a signal, the state of the corresponding transport endpoint is
T_OUTCON, allowing a further call to either t_rcvconnect(3NSL),
t_rcvdis(3NSL) or t_snddis(3NSL). When an asynchronous t_connect()
call is interrupted by the arrival of a signal, the state of the
corresponding transport endpoint is T_IDLE.

RETURN VALUES

Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate an error.

VALID STATES

T_IDLE

ERRORS

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

TACCES
The user does not have permission to use the specified
address or options.

TADDRBUSY
This transport provider does not support multiple
connections with the same local and remote addresses.
This error indicates that a connection already exists.

TBADADDR
The specified protocol address was in an incorrect
format or contained illegal information.

TBADDATA
The amount of user data specified was not within the
bounds allowed by the transport provider.

TBADF
The specified file descriptor does not refer to a
transport endpoint.

TBADOPT
The specified protocol options were in an incorrect
format or contained illegal information.

TBUFOVFLW
The number of bytes allocated for an incoming argument
(maxlen) is greater than 0 but not sufficient to store
the value of that argument. If executed in synchronous
mode, the provider's state, as seen by the user,
changes to T_DATAXFER, and the information to be
returned in rcvcall is discarded.

TLOOK
An asynchronous event has occurred on this transport
endpoint and requires immediate attention.

TNODATA
O_NONBLOCK was set, so the function successfully
initiated the connection establishment procedure, but
did not wait for a response from the remote user.

TNOTSUPPORT
This function is not supported by the underlying
transport provider.

TOUTSTATE
The communications endpoint referenced by fd is not
in one of the states in which a call to this function
is valid.

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 error
(t_errno).

TSYSERR
A system error has occurred during execution of this
function.

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 TPROTO and TADDRBUSY t_errno values can be set by the XTI
interface but not by the TLI interface.

A t_errno value that this routine can return under different
circumstances than its XTI counterpart is TBUFOVFLW. It can be
returned even when the maxlen field of the corresponding buffer has
been set to zero.

Option Buffers

The format of the options in an opt buffer is dictated by the
transport provider. Unlike the XTI interface, the TLI interface does
not fix the buffer format.

ATTRIBUTES