=head1 NAME

Net::SIP::Endpoint - Endpoint for SIP packets (UAC,UAS)

=head1 SYNOPSIS

  my $disp = Net::SIP::Dispatcher->new(...);
  my $ua = Net::SIP::Endpoint->new($disp);
  $ua->register(
	from => 'sip:me@example.com',
	contact => 'sip:me@192.168.0.1',
	registar => '192.168.0.10:5060'
  );

=head1 DESCRIPTION

The package implements a communication endpoint for SIP.
This is usually a phone, but can also be a stateful proxy (because
it retransmits packets itself).

It provides methods to send arbitrary requests but also for sending
special requests like INVITE or REGISTER. Together with
L<Net::SIP::Endpoint::Context> it implements the behavior of
the endpoint.

For incoming requests the endpoint usually communicates with
the upper layer, the application, which is the interface to
the user (e.g. let it ring for incoming calls, create response
for call accepted if user picks up phone on incoming call etc).

=head1 CONSTRUCTOR

=over 4

=item new ( DISPATCHER )

Creates a new endpoint and sets it as the receiver for incoming
packets at the L<Net::SIP::Dispatcher> DISPATCHER. The endpoint
will use DISPATCHER for outgoing packets and will receive
incoming packets from it.

=back

=head1 METHODS

=over 4

=item set_application ( APP )

Sets APP as the upper layer, e.g. the layer between the user
and the endpoint object C<$self>. APP is either an object which has
a method B<receive> or a callback usable by B<invoke_callback>
in L<Net::SIP::Util>.

The callback will be invoked with the following arguments:

=over 8

=item ENDPOINT

This is the endpoint itself, e.g. C<$self>.

=item CTX

The L<Net::SIP::Endpoint::Context> object for the current call.

=item REQUEST

The L<Net::SIP::Request> which caused the invocation of the call,
e.g. an INVITE on new calls, ACK if the peer established the call,
BYE if a call gets closed by the peer etc.

=item LEG

The L<Net::SIP::Leg> object where the call came in. Together
with FROM used to send response packet back to peer.

=item FROM

C<< "ip:port" >> of the sender of the request.

=back

It will call into APP in various incoming requests, like:

=over 8

=item INVITE

In this case APP should ring the user and while ringing send
C<< 180 Ringing >> responses back to the peer, using
C<< ENDPOINT->new_response >>. After some time it should
send a final response (like C<< 200 Ok >> if the user accepted
the call).

=item ACK

This is the sign, that the peer established the call. APP should
now expect to process incoming RTP data and send RTP data itself.

=item CANCEL, BYE

This informs APP, that the call is closed. No need for the
APP to send a response itself, this was already handled by
the endpoint (because there is no choice of responses, it
can hardly not accept a BYE).

=item other requests

Like OPTION,.. .
Theseneed to be fully handled by APP, e.g. send the appropriate
response back using C<< ENDPOINT->new_response >>.

=back

=item invite ( CTX, [ CALLBACK, BODY, %ARGS ] )

Creates a new INVITE request and delivers it to the peer.
Simply calls B<new_request> with the method 'INVITE'.
See this method for information for the arguments.

=item register ( %ARGS )

Registers endpoint at remote registrar. %ARGS needs to
be filled as follows:

=over 8

=item registrar

C<< "ip:port" >> of registrar. Mandatory.

=item from

The adress to register at the registrar. Mandatory.

=item contact

The contact, under which C<from> will be registered. Mandatory.

=item auth

Authorization info, see method B<authorize> in L<Net::SIP::Request>
for information about the format. Optional.

=item expires

Expires time. Optional, defaults to 900.

=item callback

Optional callback, e.g. called if requests come in from the
peer on the call created for the registration. See B<invoke_callback>
in L<Net::SIP::Util> for the format.

=back

All other keys will be used as header keys in generating the
L<Net::SIP::Request> object.

=item new_request ( METHOD, CTX, [ CALLBACK, BODY, %ARGS ] )

Method is the uppercase name of the method for which a request
should be generated. It can also be already a L<Net::SIP::Request>
object in which case no new request object will be generated,
but the provided delivered.

CTX is either an existing L<Net::SIP::Endpoint::Context> object
or a hash reference which will be used to construct one. It contains
information about C<from> and C<to> etc. See
constructor in L<Net::SIP::Endpoint::Context> for details.

If it is an existing CTX it has to be one which is already managed
by this endpoint (e.g. one returned by this method), the endpoint
will only manage CTX which it created itself so that a context
cannot be shared between multiple endpoints.

CALLBACK is a callback usable by B<invoke_callback> in L<Net::SIP::Util>.
If defined it will be set up as the new default callback for the
context.

BODY is a string or an object for the SIP body accepted by the
constructor of L<Net::SIP::Request>.  See there.

Anything in %ARGS will be used to construct the SIP header. See
constructor in L<Net::SIP::Request>.

It returns the L<Net::SIP::Endpoint::Context> object for this
request which can be then used for further requests in the same
call.

=item cancel_invite ( CTX, REQUEST, CALLBACK )

Cancel the given request within the given context (e.g send CANCEL request).
If no REQUEST is given it will cancel the most recent INVITE. Returns the
number of requests canceled, e.g. 0 or 1.

CALLBACK will be used as the callback for the CANCEL request it sends using
B<new_request>.

=item close_context ( CTX )

Delete L<Net::SIP::Endpoint::Context> object CTX from the list
of active calls.

=item receive ( PACKET, LEG, FROM )

Called from dispatcher on incoming packets.

PACKET is the incoming L<Net::SIP::Packet>, LEG the L<Net::SIP::Leg>
where the packet came in and FROM the C<< "ip:port" >> of the sender.

Just forwards to B<receive_request> or B<receive_response> based
on the type of packet.

=item receive_response ( RESPONSE, LEG, FROM )

Handles incoming response packets. Tries to find an active call based
on the C<Call-Id> header in the packet. If none was found it
will drop the packet, otherwise call B<handle_response> on the
call context object (L<Net::SIP::Endpoint::Context>).

=item receive_request ( REQUEST, LEG, FROM )

Handles incoming requests.

If there is already a call context for this B<Call-Id> in the request
it will use it, otherwise it will create a L<Net::SIP::Endpoint::Context>
object based on the information in the request (C<from>, C<to>, C<contact>,... ).

Calls B<handle_request> on the existing/new context object.

=item new_response ( CTX, RESPONSE, LEG, ADDR )

Delivers L<Net::SIP::Response> packet RESPONSE through the endpoints
dispatcher to ADDR (C<< "ip:port" >>) using L<Net::SIP::Leg> LEG.
LEG and ADDR are usually the leg and the senders address where the
associated request came in.

CTX is the context from the call, where the associated request came in.

If the response is a 2xx response to a INVITE and no C<contact> header
is given as required from the RFC it will add one based on the CTX.

=back