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


t_listen - listen for a connection indication


#include <xti.h>

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


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

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.


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.




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

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

The argument qlen of the endpoint referenced by fd is

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).

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

O_NONBLOCK was set, but no connection indications had been

This function is not supported by the underlying transport

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

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 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).

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 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

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.


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

|MT Level | Safe |


fcntl(2), t_accept(3NSL), t_alloc(3NSL), t_bind(3NSL), t_connect(3NSL),
t_open(3NSL), t_optmgmt(3NSL), t_rcvconnect(3NSL), t_snddis(3NSL),


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)