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_IDLEERRORS
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
See
attributes(7) for descriptions of the following attributes:
+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT Level | Safe |
+---------------+-----------------+
SEE ALSO
fcntl(2),
t_accept(3NSL),
t_alloc(3NSL),
t_getinfo(3NSL),
t_listen(3NSL),
t_open(3NSL),
t_optmgmt(3NSL),
t_rcvconnect(3NSL),
t_rcvdis(3NSL),
t_snddis(3NSL),
attributes May 7, 1998
T_CONNECT(3NSL)