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


t_accept - accept a connection request


#include <xti.h>

int t_accept(int fd, int resfd, const struct t_call *call);


This routine is part of the XTI interfaces that 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, a different header
file, tiuser.h, must be used. Refer to the TLI COMPATIBILITY section for
a description of differences between the two interfaces.

This function is issued by a transport user to accept a connection
request. The parameter fd identifies the local transport endpoint where
the connection indication arrived; resfd specifies the local transport
endpoint where the connection is to be established, and call contains
information required by the transport provider to complete the
connection. The parameter call points to a t_call structure which
contains the following members:

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

In call, addr is the protocol address of the calling transport user, opt
indicates any options associated with the connection, udata points to any
user data to be returned to the caller, and sequence is the value
returned by t_listen(3NSL) that uniquely associates the response with a
previously received connection indication. The address of the caller,
addr may be null (length zero). Where addr is not null then it may
optionally be checked by XTI.

A transport user may accept a connection on either the same, or on a
different, local transport endpoint than the one on which the connection
indication arrived. Before the connection can be accepted on the same
endpoint (resfd==fd), the user must have responded to any previous
connection indications received on that transport endpoint by means of
t_accept() or t_snddis(3NSL). Otherwise, t_accept() will fail and set
t_errno to TINDOUT.

If a different transport endpoint is specified (resfd!=fd), then the user
may or may not choose to bind the endpoint before the t_accept() is
issued. If the endpoint is not bound prior to the t_accept(), the
endpoint must be in the T_UNBND state before the t_accept() is issued,
and the transport provider will automatically bind it to an address that
is appropriate for the protocol concerned. If the transport user chooses
to bind the endpoint it must be bound to a protocol address with a qlen
of zero and must be in the T_IDLE state before the t_accept() is issued.

Responding endpoints should be supplied to t_accept() in the state

The call to t_accept() may fail with t_errno set to TLOOK if there are
indications (for example connect or disconnect) waiting to be received on
endpoint fd. Applications should be prepared for such a failure.

The udata argument enables the called transport user to send user data to
the caller and 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 field of
udata is zero, no data will be sent to the caller. All the maxlen fields
are meaningless.

When the user does not indicate any option (call->opt.len = 0) the
connection shall be accepted with the option values currently set for the
responding endpoint resfd.


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.



resfd (fd!=resfd): T_IDLE, T_UNBND


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

The user does not have permission to accept a connection
on the responding transport endpoint or to use the
specified options.

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

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

The file descriptor fd or resfd does not refer to a
transport endpoint.

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

Either an invalid sequence number was specified, or a
valid sequence number was specified but the connection
request was aborted by the peer. In the latter case, its
T_DISCONNECT event will be received on the listening

The function was called with fd==resfd but there are
outstanding connection indications on the endpoint.
Those other connection indications must be handled
either by rejecting them by means of t_snddis(3NSL) or
accepting them on a different endpoint by means of

An asynchronous event has occurred on the transport
endpoint referenced by fd and requires immediate

This function is not supported by the underlying
transport provider.

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

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).

The file descriptors fd and resfd do not refer to the
same transport provider.

This transport provider requires both fd and resfd to be
bound to the same address. This error results if they
are not.

The endpoint referenced by resfd (where resfd != fd) was
bound to a protocol address with a qlen that is greater
than zero.

A system error has occurred during execution of this


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 t_errno values that can be set by the XTI interface and cannot be set
by the TLI interface are:






Option Buffer

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


See attributes(7) for descriptions of the following attributes:

|MT Level | Safe |


t_connect(3NSL), t_getinfo(3NSL), t_getstate(3NSL), t_listen(3NSL),
t_open(3NSL), t_optmgmt(3NSL), t_rcvconnect(3NSL), t_snddis(3NSL),


There may be transport provider-specific restrictions on address binding.

Some transport providers do not differentiate between a connection
indication and the connection itself. If the connection has already been
established after a successful return of t_listen(3NSL), t_accept() will
assign the existing connection to the transport endpoint specified by

May 1, 1998 T_ACCEPT(3NSL)