NAME
    ZeroMQ - A ZeroMQ2 wrapper for Perl

SYNOPSIS ( HIGH-LEVEL API )
        # echo server
        use ZeroMQ qw/:all/;

        my $cxt = ZeroMQ::Context->new;
        my $sock = $cxt->socket(ZMQ_REP);
        $sock->bind($addr);
  
        my $msg;
        foreach (1..$roundtrip_count) {
            $msg = $sock->recv();
            $sock->send($msg);
        }

        # json (if JSON.pm is available)
        $sock->send_as( json => { foo => "bar" } );
        my $thing = $sock->recv_as( "json" );

        # custom serialization
        ZeroMQ::register_read_type(myformat => sub { ... });
        ZeroMQ::register_write_type(myformat => sub { .. });

        $sock->send_as( myformat => $data ); # serialize using above callback
        my $thing = $sock->recv_as( "myformat" );

SYNOPSIS ( LOW-LEVEL API )
        use ZeroMQ::Raw;

        my $ctxt = zmq_init($threads);
        my $rv   = zmq_term($ctxt);

        my $msg  = zmq_msg_init();
        my $msg  = zmq_msg_init_size( $size );
        my $msg  = zmq_msg_init_data( $data );
        my $rv   = zmq_msg_close( $msg );
        my $rv   = zmq_msg_move( $dest, $src );
        my $rv   = zmq_msg_copy( $dest, $src );
        my $data = zmq_msg_data( $msg );
        my $size = zmq_msg_size( $msg);

        my $sock = zmq_socket( $ctxt, $type );
        my $rv   = zmq_close( $sock );
        my $rv   = zmq_setsockopt( $socket, $option, $value );
        my $val  = zmq_getsockopt( $socket, $option );
        my $rv   = zmq_bind( $sock, $addr );
        my $rv   = zmq_send( $sock, $msg, $flags );
        my $msg  = zmq_recv( $sock, $flags );

DESCRIPTION
    The "ZeroMQ" module is a wrapper of the 0MQ message passing library for
    Perl. It's a thin wrapper around the C API. Please read
    <http://zeromq.org> for more details on ZeroMQ.

CLASS WALKTHROUGH
    ZeroMQ::Raw
        Use ZeroMQ::Raw to get access to the C API such as "zmq_init",
        "zmq_socket", et al. Functions provided in this low level API should
        follow the C API exactly.

    ZeroMQ::Constants
        ZeroMQ::Constants contains all of the constants that are known to be
        extractable from zmq.h. Do note that sometimes the list changes due
        to additions/deprecations in the underlying zeromq2 library. We try
        to do our best to make things available (at least to warn you that
        some symbols are deprecated), but it may not always be possible.

    ZeroMQ::Context
    ZeroMQ::Socket
    ZeroMQ::Message
        ZeroMQ::Context, ZeroMQ::Socket, ZeroMQ::Message contain the
        high-level, more perl-ish interface to the zeromq functionalities.

    ZeroMQ
        Loading "ZeroMQ" will make the ZeroMQ::Context, ZeroMQ::Socket, and
        ZeroMQ::Message classes available as well.

BASIC USAGE
    To start using ZeroMQ, you need to create a context object, then as many
    ZeroMQ::Socket as you need:

        my $ctxt = ZeroMQ::Context->new;
        my $socket = $ctxt->socket( ... options );

    You need to call "bind()" or "connect()" on the socket, depending on
    your usage. For example on a typical server-client model you would write
    on the server side:

        $socket->bind( "tcp://127.0.0.1:9999" );

    and on the client side:

        $socket->connect( "tcp://127.0.0.1:9999" );

    The underlying zeromq library offers TCP, multicast, in-process, and ipc
    connection patterns. Read the zeromq manual for more details on other
    ways to setup the socket.

    When sending data, you can either pass a ZeroMQ::Message object or a
    Perl string.

        # the following two send() calls are equivalent
        my $msg = ZeroMQ::Message->new( "a simple message" );
        $socket->send( $msg );
        $socket->send( "a simple message" );

    In most cases using ZeroMQ::Message is redundunt, so you will most
    likely use the string version.

    To receive, simply call "recv()" on the socket

        my $msg = $socket->recv;

    The received message is an instance of ZeroMQ::Message object, and you
    can access the content held in the message via the "data()" method:

        my $data = $msg->data;

SERIALIZATION
    ZeroMQ.pm comes with a simple serialization/deserialization mechanism.

    To serialize, use "register_write_type()" to register a name and an
    associated callback to serialize the data. For example, for JSON we do
    the following (this is already done for you in ZeroMQ.pm if you have
    JSON.pm installed):

        use JSON ();
        ZeroMQ::register_write_type('json' => \&JSON::encode_json);
        ZeroMQ::register_read_type('json' => \&JSON::decode_json);

    Then you can use "send_as()" and "recv_as()" to specify the
    serialization type as the first argument:

        my $ctxt = ZeroMQ::Context->new();
        my $sock = $ctxt->socket( ZMQ_REQ );

        $sock->send_as( json => $complex_perl_data_structure );

    The otherside will receive a JSON encoded data. The receivind side can
    be written as:

        my $ctxt = ZeroMQ::Context->new();
        my $sock = $ctxt->socket( ZMQ_REP );

        my $complex_perl_data_structure = $sock->recv_as( 'json' );

    If you have JSON.pm (must be 2.00 or above), then the JSON serializer /
    deserializer is automatically enabled. If you want to tweak the
    serializer option, do something like this:

        my $coder = JSON->new->utf8->pretty; # pretty print
        ZeroMQ::register_write_type( json => sub { $coder->encode($_[0]) } );
        ZeroMQ::register_read_type( json => sub { $coder->decode($_[0]) } );

    Note that this will have a GLOBAL effect. If you want to change only
    your application, use a name that's different from 'json'.

ASYNCHRONOUS I/O WITH ZEROMQ
    By default ZeroMQ comes with its own zmq_poll() mechanism that can
    handle non-blocking sockets. You can use this by creating calling
    zmq_poll with a list of hashrefs:

        zmq_poll([
            {
                fd => fileno(STDOUT),
                events => ZMQ_POLLOUT,
                callback => \&callback,
            },
            {
                socket => $zmq_socket,
                events => ZMQ_POLLIN,
                callback => \&callback
            },
        ], $timeout );

    Unfortunately this custom polling scheme doesn't play too well with
    AnyEvent. As of zeromq2-2.1.0, you can use getsockopt to retrieve the
    underlying file descriptor, so use that to integrate ZeroMQ and
    AnyEvent:

        my $fh = zmq_getsockopt( $socket, ZMQ_FD );
        my $w; $w = AE::io $fh, 0, sub {
            undef $w;
            print $fh "Hello\n";
        };

NOTES ON MULTI-PROCESS and MULTI-THREADED USAGE
    ZeroMQ works on both multi-process and multi-threaded use cases, but you
    need to be careful bout sharing ZeroMQ objects.

    For multi-process environments, you should not be sharing the context
    object. Create separate contexts for each process, and therefore you
    shouldn't be sharing the socket objects either.

    For multi-thread environemnts, you can share the same context object.
    However you cannot share sockets.

FUNCTIONS
  version()
    Returns the version of the underlying zeromq library that is being
    linked. In scalar context, returns a dotted version string. In list
    context, returns a 3-element list of the version numbers:

        my $version_string = ZeroMQ::version();
        my ($major, $minor, $patch) = ZeroMQ::version();

  device($type, $sock1, $sock2)
  register_read_type($name, \&callback)
    Register a read callback for a given $name. This is used in "recv_as()".
    The callback receives the data received from the socket.

  register_write_type($name, \&callback)
    Register a write callback for a given $name. This is used in "send_as()"
    The callback receives the Perl structure given to "send_as()"

CAVEATS
    This is an early release. Proceed with caution, please report (or better
    yet: fix) bugs you encounter. Tested againt 0MQ 2.1.0.

SEE ALSO
    ZeroMQ::Context, ZeroMQ::Socket, ZeroMQ::Message

    <http://zeromq.org>

AUTHOR
    Daisuke Maki "<daisuke@endeworks.jp>"

    Steffen Mueller, "<smueller@cpan.org>"

COPYRIGHT AND LICENSE
    The ZeroMQ module is

    Copyright (C) 2010 by Daisuke Maki

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.0 or, at
    your option, any later version of Perl 5 you may have available.

