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 TPROT0, 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

See attributes(5) for descriptions of the following attributes:

See Also

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), attributes(5)

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.