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

NAME

t_listen - listen for a connection indication

SYNOPSIS

#include <xti.h>

int t_listen(int fd, struct t_call *call);

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 listens for a connection indication from a calling
transport user. The argument fd identifies the local transport
endpoint where connection indications arrive, and on return, call
contains information describing the connection indication. 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 returns the protocol address of the calling transport
user. This address is in a format usable in future calls to
t_connect(3NSL). Note, however that t_connect(3NSL) may fail for
other reasons, for example TADDRBUSY. opt returns options associated
with the connection indication, udata returns any user data sent by
the caller on the connection request, and sequence is a number that
uniquely identifies the returned connection indication. The value of
sequence enables the user to listen for multiple connection
indications before responding to any of them.

Since this function returns values for the addr, opt and udata fields
of call, the maxlen field of each must be set before issuing the
t_listen() to indicate the maximum size of the buffer for each. If
the maxlen field of call->addr, call->opt or call->udata is set to
zero, no information is returned for this parameter.

By default, t_listen() executes in synchronous mode and waits for a
connection indication to arrive before returning to the user.
However, if O_NONBLOCK is set via t_open(3NSL) or fcntl(2),
t_listen() executes asynchronously, reducing to a poll for existing
connection indications. If none are available, it returns -1 and
sets t_errno to TNODATA.

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, T_INCON

ERRORS

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

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

TBADQLEN
The argument qlen of the endpoint referenced by fd is
zero.

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. The provider's state, as
seen by the user, changes to T_INCON, and the
connection indication information to be returned in
call is discarded. The value of sequence returned can
be used to do a t_snddis(3NSL).

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

TNODATA
O_NONBLOCK was set, but no connection indications had
been queued.

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).

TQFULL
The maximum number of outstanding connection
indications has been reached for the endpoint
referenced by fd. Note that a subsequent call to
t_listen() may block until another incoming connection
indication is available. This can only occur if at
least one of the outstanding connection indications
becomes no longer outstanding, for example through a
call to t_accept(3NSL).

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 t_errno values TPROTO, TBADQLEN, and TQFULL 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

WARNINGS

Some transport providers do not differentiate between a connection
indication and the connection itself. If this is the case, a
successful return of t_listen() indicates an existing connection.

February 18, 2015 T_LISTEN(3NSL)