NAME

t_listen - listen for a connection indication

SYNOPSIS

#include <xti.h>

int t_listen(
    int fd,
    struct t_call *call)

DESCRIPTION

Parameters	Before call	After call
fd	x	/
call->addr.maxlen	x	=
call->addr.len	/	x
call->addr.buf	?	(?)
call->opt.maxlen	x	=
call->opt.len	/	x
call->opt.buf	?	(?)
call->udata.maxlen	x	=
call->udata.len	/	x
call->udata.buf	?	(?)
call->sequence	/	x

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(). Note, however that t_connect() 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() or fcntl(), 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].

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().

[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().

[TSYSERR]

A system error has occurred during execution of this function.

CAVEATS

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 (see Internet Protocol-specific Information ).

RETURN VALUE

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.

SEE ALSO

fcntl(), t_accept(), t_alloc(), t_bind(), t_connect(), t_open(), t_optmgmt(), t_rcvconnect().

CHANGE HISTORY

Issue 4

The SYNOPSIS section is placed in the form of a standard C function prototype.