=head1 NAME

Net::SIP - Framework SIP (Voice Over IP, RFC3261)

=head1 SYNOPSIS

...

=head1 DESCRIPTION

Net::SIP consists of packages for handling the SIP packets,
for transport of the packets, for processing the packets
and on top of all that a simplified layer for common tasks.

Addionally L<Net::SIP::Util> provides utility functions
and L<Net::SIP::Debug> provides a debugging layer used
by all these packages. Especially it provides the function
B<invoke_callback> which is used for all callbacks unless
documentation specifies otherwise. This function
supports a variety of different callback styles.

For first and simple applications you best start with L<Net::SIP::Simple>.
If this is no longer enough you might look at the details of
L<Net::SIP::Dispatcher>, L<Net::SIP::Endpoint>,
L<Net::SIP::Register> and L<Net::SIP::StatelessProxy>.
Although these packages are in itself well documented the functionality
and the design is best understandable if you look how it gets used
in the source of L<Net::SIP::Simple>.

=head2 SIP packet handling

=over 4

=item L<Net::SIP::Packet>

The base class for handling SIP packets and provides ways to
parse, construct and manipulate SIP packets.

=item L<Net::SIP::Request>

Derived from L<Net::SIP::Packet> and handles the request packets.
Provides ways to create special requests like ACK or CANCEL based
on previous requests and responses, for creating responses based
on requests, for authorization of requests.

=item L<Net::SIP::Response>

Derived from L<Net::SIP::Packet> and handles the response packets.

=item L<Net::SIP::SDP>

Handles SDP bodies from SIP packets. Provides ways to parse, construct
these bodies, to get media information from them and to manipulate the
SDP data for NAT etc.

=back

=head2 Transport of SIP packets

=over 4

=item L<Net::SIP::Leg>

Encapsulates socket for transport of packet. Provides way to find out,
if target is reachable through this socket. Prepares incoming, outgoing
and forwarding packets by removing or adding header like B<Via>,
B<Record-Route>.

=item L<Net::SIP::Dispatcher>

Handles new packets coming in through a L<Net::SIP::Leg>.
Delivers outgoing packets through the appropriate L<Net::SIP::Leg>.
Handles timeouts and retransmission of outgoing packets, lookup
of the appropriate leg through DNS etc.

=item L<Net::SIP::Dispatcher::Eventloop>

Simple implementation of an event loop for handling socket events
and timers.
Can be replaced to integrate into other event loops, like L<Tk>,
L<Lib::Event> or L<POE>.

=back

=head2 Processing of SIP packets, application layer

=over 4

=item L<Net::SIP::Endpoint>

Implements a SIP endpoint (UAC,UAS). Provides ways to INVITE or BYE
calls or to handle incoming calls. Calls themselves will be handled by
L<Net::SIP::Endpoint::Context>.

=item L<Net::SIP::Registrar>

Simple implementation of a registrar.

=item L<Net::SIP::StatelessProxy>

Simple implementation of a stateless proxy. Stateful proxies should
probably be implemented by putting multiple L<Net::SIP::Endpoint>s
together.

=item L<Net::SIP::Blocker>

Can block requests by method name with custom error code.

=item L<Net::SIP::ReceiveChain>

Can contain various objects for processing objects. Useful
in connection with L<Net::SIP::Authorize>.

=item L<Net::SIP::Redirect>

Works together with a registrar and redirects requests.

=item L<Net::SIP::Authorize>

If put into a L<Net::SIP::ReceiveChain> it requests and checks
authorization and gives only authorized requests to the next
member of the chain.

=back

=head2 Simplified Layer for common tasks

=over 4

=item Net::SIP::Simple

Provides simple layer for common tasks and tests, like sending
a voice message to somebody, receiving a message or even implementing
an answer machine. Together with L<Net::SIP::Simple::RTP> it
is possible to handle simple RTP data (PCMU/8000).

=back

=head2 Error handling

Unless otherwise documented the common way to propagate errors is to
raise an exception, e.g. call die(). This might especially happen
when parsing packets from strings, so unless you want to crash your
application on bad input you should catch these exceptions with
eval.

=head1 EXPORTS

By default nothing is exported. There are various arguments for
exporting:

=over 4

=item :alias

Exports constants as aliases for the Net::SIP::* packages, e.g.
'Simple' for 'Net::SIP::Simple', 'Registrar' for 'Net::SIP::Registrar',
'Packet' for 'Net::SIP::Packet', 'NATHelper_Client' for 'Net::SIP::NATHelper::Client'
 etc.

=item :util

Exports everything (tag ':all') from L<Net::SIP::Util>.

=item :debug

Exports the default exports from L<Net::SIP::Debug>.

=item :all

Everything from ':debug', ':util' and ':alias'.

=item rtp=MINPORT-MAXPORT|rtp:MINPORT-MAXPORT

Set the range of ports to be used for creating RTP sockets to MINPORT..MAXPORT.
This affects L<Net::SIP::Util::create_rtp_sockets>.

=item debug=LEVEL|debug:LEVEL

Set Debugging level to LEVEL

=item string

Strings where the first character is upper case will be interpreted
as aliases for Net::SIP::* and it will try to export it. If
the first character is lower case it will try to import it from
L<Net::SIP::Util>.

=back

=head2 EXAMPLES

  use Net::SIP 'invoke_callback'; # use Net::SIP::Util 'invoke_callback'
  use Net::SIP ':debug';          # use Net::SIP::Debug
  use Net::SIP ':util';           # use Net::SIP::Util ':all'

  use Net::SIP ':alias';
  Packet->new( ... );             # Net::SIP::Packet->new( ... )


  # restrict rtp sockets from command line
  perl -MNet::SIP=rtp:4000-4010 program.pl

=head1 BUGS

Support for TCP and SIPS and not or not fully implemented.

=head1 COPYRIGHT

This module and are modules in the Net::SIP Hierarchy distributed
together with this module are copyright (c) 2006-2013, Steffen Ullrich.
All Rights Reserved.
These modules are free software. They may be used, redistributed
and/or modified under the same terms as Perl itself.