ZMQ::LibZMQ4(3)

💖 ZMQ::LibZMQ4 💖

okay bestie, welcome to the manual page for ZMQ::LibZMQ4, which lives in the User Contributed Perl Documentation section (section 3, the library-calls one, you know the vibe) 🫶

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✨ NAME ✨

ZMQ::LibZMQ4 — a libzmq 4.x wrapper for Perl 🎀

like, it's a Perl wrapper. for libzmq. version 4.x. that's the whole thing. slay.

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✨ SYNOPSIS ✨

here's the whole vibe in one code block, no cap:

use ZMQ::LibZMQ4;
use ZMQ::Constants; # separate module

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, $buffer, $length, $flags );
my $msg  = zmq_sendmsg( $sock, $msg, $flags );
my $rv   = zmq_recv( $sock, $buffer, $length, $flags );
my $msg  = zmq_recvmsg( $sock, $flags );

literally the entire module in one screenshot 💅

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✨ INSTALLATION ✨

🦋 if you have libzmq registered with pkg-config

the easy path, the main character path:

perl Makefile.PL
make
make test
make install

🦋 if you DON'T have pkg-config, and libzmq lives under /usr/local/libzmq

bestie just tell it where home is:

ZMQ_HOME=/usr/local/libzmq \
    perl Makefile.PL
make
make test
make install

🦋 if you wanna customize include directories and such

okay DIY queen, go off:

ZMQ_INCLUDES=/path/to/libzmq/include \
ZMQ_LIBS=/path/to/libzmq/lib \
ZMQ_H=/path/to/libzmq/include/zmq.h \
    perl Makefile.PL
make
make test
make install

🦋 if you wanna compile with debugging on

perl Makefile.PL -g

yes, -g. that's it. that's the whole flag. ✨

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✨ DESCRIPTION ✨

so the ZMQ::LibZMQ4 module is a wrapper of the 0MQ message passing library for Perl. 💖

before you start using this module, please please please make sure you have read and understood the zguide. fr fr, it's not optional, it's the syllabus:

http://zguide.zeromq.org/page:all

for the specifics on each function, please refer to their documentation for the definitive explanation of each — the C docs are the source of truth, not this page:

http://api.zeromq.org/

this module is merely a thin wrapper around the C API. you need to understand how the C API works in order to properly use this module. it is not gonna hold your hand, bestie, it's giving "here's a direct line to C, good luck, mwah" 😭

note that this is a wrapper for libzmq 4.x. for 2.x, you need to check ZMQ::LibZMQ2 and for 3.x, you need to check ZMQ::LibZMQ3 🌈

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✨ BASIC USAGE ✨

please make sure you already have the ZMQ::Constants module. if you installed ZMQ::LibZMQ4 from CPAN via cpan/cpanm, it should have already been installed for you. all socket types and other flags are declared in this module. 🎀

to start using ZMQ::LibZMQ4, you need to create a context object, then as many ZMQ::LibZMQ4::Socket objects as you need:

my $ctxt = zmq_init;
my $socket = zmq_socket( $ctxt, ... options );

you need to call zmq_bind() or zmq_connect() on the socket, depending on your usage. for example on a typical server-client model you would write on the server side:

zmq_bind( $socket, "tcp://127.0.0.1:9999" );

and on the client side:

zmq_connect( $socket, "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 ZMQ::LibZMQ4::Message object or a Perl string. both are valid, it's giving flexible:

# the following two send() calls are equivalent
my $msg = zmq_msg_init_data( "a simple message" );
zmq_sendmsg( $socket, $msg );

zmq_sendmsg( $socket, "a simple message" );

in most cases using ZMQ::LibZMQ4::Message is redundant, so you will most likely use the string version. 🍓

to receive, simply call zmq_recvmsg() on the socket:

my $msg = zmq_recvmsg( $socket );

the received message is an instance of ZMQ::LibZMQ4::Message object, and you can access the content held in the message via the zmq_msg_data() method:

my $data = zmq_msg_data( $msg );

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✨ WHEN IN DOUBT ✨

0MQ is a relatively large framework, and to use it you need to be comfortable with a lot of concepts. if you think this module is not behaving like you expect it to, please read the documents for the C API. i'm not being shady, i'm being honest, the C docs are the moment 💜

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✨ ASYNCHRONOUS I/O WITH ZEROMQ ✨

by default 0MQ comes with its own zmq_poll() mechanism that can handle non-blocking sockets. you can use this by 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. it's not toxic, it's just not compatible, okay? 🙈

fortunately you can use getsockopt to retrieve the underlying file descriptor, so use that to integrate ZMQ::LibZMQ4 and AnyEvent:

my $socket = zmq_socket( $ctxt, ZMQ_REP );
my $fh = zmq_getsockopt( $socket, ZMQ_FD );
my $w; $w = AE::io $fh, 0, sub {
    while ( my $msg = zmq_recv( $socket, ZMQ_RCVMORE ) ) {
        # do something with $msg;
    }
    undef $w;
};

there it is. the AnyEvent glow-up. iconic. ✨

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✨ NOTES ON MULTI-PROCESS and MULTI-THREADED USAGE ✨

0MQ works on both multi-process and multi-threaded use cases, but you need to be careful about sharing ZMQ::LibZMQ4 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 environments, you can share the same context object. however you cannot share sockets. note that while the Perl Socket objects survive between threads, their underlying C structures do not, and you will get an error if you try to use them between sockets. 💀

tl;dr: contexts can be shared between threads, sockets cannot, and the Perl-level socket objects are lying to you if you think they'll survive a thread hop. 🫶

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✨ FUNCTIONS ✨

ZMQ::LibZMQ4 is literally trying to stick to the libzmq interface as much as possible. Unless there's a structural problem (like, an underlying pointer the Perl binding expected was missing), no function should throw an exception. Periodt. 💅

Return values should resemble that of libzmq, except for when new data is allocated and returned to you — that includes things like zmq_init(), zmq_socket(), zmq_msg_data(), etc. 🫶

Where applicable, $! should be updated to match the value set by libzmq, so you should be able to do:

my $cxt = zmq_init();
if (! $cxt) {
    die "zmq_init() failed with $!";
}

---

$errno = zmq_errno()

Returns the value of errno variable for the calling thread. You normally should not need to use this function. See the man page for zmq_errno() provided by libzmq. 🧚

$string = zmq_strerror( $errno )

Returns the string representation of $errno. Use this to stringify errors that libzmq provides. ✨

$cxt = zmq_init( $threads )

Creates a new context object. The $threads argument is optional. Context objects can be reused across threads. 👑

Returns undef upon error, and sets $!.

Note: Deprecated in libzmq, but the Perl binding will silently fallback to using zmq_ctx_new(), if available.

$cxt = zmq_ctx_new( $threads );

Creates a new context object. The $threads argument is optional. Context objects can be reused across threads. 💖

Returns undef upon error, and sets $!.

Note: may not be available depending on your libzmq version.

$rv = zmq_ctx_get( $cxt, $option )

Gets the value for the given option. 🔍

Returns -1 status upon failure, and sets $!.

Note: may not be available depending on your libzmq version.

$rv = zmq_ctx_set( $cxt, $option, $value )

Sets the value for the given option. 💅

Returns a non-zero status upon failure, and sets $!.

Note: may not be available depending on your libzmq version.

$rv = zmq_term( $cxt )

Terminates the context. Be careful, as it might hang if you have pending socket operations. 😭

Returns a non-zero status upon failure, and sets $!.

Note: Deprecated in libzmq, but the Perl binding will silently fallback to using zmq_ctx_destroy(), if available.

$rv = zmq_ctx_destroy( $cxt )

Terminates the context. Be careful, as it might hang if you have pending socket operations. 💀

Returns a non-zero status upon failure, and sets $!.

Note: may not be available depending on your libzmq version.

$socket = zmq_socket( $cxt, $socket_type )

Creates a new socket object. $socket_types are constants declared in ZMQ::Constants. Sockets cannot be reused across threads. 🌈

Returns undef upon error, and sets $!.

$rv = zmq_bind( $sock, $address )

Binds the socket to listen to specified $address. 🎀

Returns a non-zero status upon failure, and sets $!

$rv = zmq_unbind( $sock, $address )

Stops listening on this endpoint. 🙈

Returns a non-zero status upon failure, and sets $!

Note: may not be available depending on your libzmq version.

$rv = zmq_connect( $sock, $address )

Connects the socket to the specified $address. 🔌

Returns a non-zero status upon failure, and sets $!

$rv = zmq_disconnect( $sock, $address )

Disconnects the socket from the specified $address. ✂️

Returns a non-zero status upon failure, and sets $!

Note: may not be available depending on your libzmq version.

$rv = zmq_close( $sock )

Closes the socket explicitly. 🚪

Returns a non-zero status upon failure, and sets $!.

$value = zmq_getsockopt( $socket, $option )

Gets the value of the specified option. 👀

If the particular version of ZMQ::LibZMQ4 does not implement the named socket option, an exception will be thrown:

/* barfs, because we don't know what type this new option is */
zmq_getsockopt( $socket, ZMQ_NEW_SHINY_OPTION );

In this case you can either use ZMQ::Constants, or you can use one of the utility functions that ZMQ::LibZMQ4 provides. 🛠️

Using ZMQ::Constants

ZMQ::LibZMQ4 internally refers to ZMQ::Constants to learn about the type of a socket option. You can easily add new constants to this map:

use ZMQ::Constants;
ZMQ::Constants::add_sockopt_type( "int" => ZMQ_NEW_SHINY_OPTION );

# Then elsewhere...
my $value = zmq_getsockopt( $socket, ZMQ_NEW_SHINY_OPTION );

Using utilities in ZMQ::LibZMQ4

/* say you know that the value is an int, int64, uint64, or char *
   by reading the zmq docs */
$int    = zmq_getsockopt_int( $socket, ZMQ_NEW_SHINY_OPTION );
$int64  = zmq_getsockopt_int64( $socket, ZMQ_NEW_SHINY_OPTION );
$uint64 = zmq_getsockopt_uint64( $socket, ZMQ_NEW_SHINY_OPTION );
$string = zmq_getsockopt_string( $socket, ZMQ_NEW_SHINY_OPTION );

$status = zmq_setsockopt( $socket, $option, $value )

Sets the value of the specified option. Returns the status. ✨

See zmq_getsockopt() if you have problems with ZMQ::LibZMQ4 not knowing the type of the option.

$bytes = zmq_send($sock, $buffer, $size, $flags)

Queues $size bytes from $buffer to be sent from the socket. Argument $flags may be omitted. If $size is -1, then the size of the buffer calculated via SvPV() will be used. 📤

Returns the number of bytes sent on success (which should be exact $size)

Returns -1 upon failure, and sets $!.

$rv = zmq_sendmsg($sock, $message, $flags)

Queues $message to be sent via $sock. Argument $flags may be omitted. 📨

If $message is a non-ref, creates a new ZMQ::LibZMQ4::Message object via zmq_msg_init_data(), and uses that to pass to the underlying C layer..

Returns the number of bytes sent on success (which should be exact $size)

Returns -1 upon failure, and sets $!.

Note: Deprecated in favor of zmq_msg_send(), and may not be available depending on your libzmq version.

$rv = zmq_msg_send($message, $sock, $flags)

Queues $message to be sent via $sock. Argument $flags may be omitted. 💌

If $message is a non-ref, creates a new ZMQ::LibZMQ4::Message object via zmq_msg_init_data(), and uses that to pass to the underlying C layer..

Returns the number of bytes sent on success (which should be exact $size)

Returns -1 upon failure, and sets $!.

Note: may not be available depending on your libzmq version.

$rv = zmq_recv($sock, $buffer, $len, $flags)

Receives a new message from $sock, and store the message payload in $buffer, up to $len bytes. Argument $flags may be omitted. 📥

Returns the number of bytes in the original message, which may exceed $len (if you have $rv > $len, then the message was truncated).

Returns -1 upon failure, and sets $!.

$message = zmq_recvmsg($sock, $flags)

Receives a new message from $sock. Argument $flags may be omitted. Returns the message object. 💬

Returns undef upon failure, and sets $!.

Note: Although this function is marked as deprecated in libzmq3, it will stay in the Perl binding as the official short-circuit version of zmq_msg_recv(), so that you don't have to create a message object every time.

$rv = zmq_msg_recv($msg, $sock, $flags)

Receives a new message from $sock, and writes the new content to $msg. Argument $flags may be omitted. 📩

Returns the number of bytes in the message if successful.

Returns -1 upon failure, and sets $!.

Other than the fact that libzmq has deprecated zmq_recvmsg(), this construct is useful if you don't want to allocate a message struct for every recv call:

my $msg = zmq_msg_init();
while (1) {
    my $rv = zmq_msg_recv($msg, $sock, $flags);
    ...
}

Note: may not be available depending on your libzmq version

$msg = zmq_msg_init()

Creates a new message object. 🎁

Returns undef upon failure, and sets $!.

$msg = zmq_msg_init_data($string)

Creates a new message object, and sets the message payload to the string in $string. 📝

Returns undef upon failure, and sets $!.

$msg = zmq_msg_init_size($size)

Creates a new message object, allocating $size bytes. This call isn't so useful from within Perl 🤷‍♀️

Returns undef upon failure, and sets $!.

$string = zmq_msg_data( $msg )

Returns the payload contained in $msg 📦

$size = zmq_msg_size( $msg )

Returns the size of payload contained in $msg 📏

zmq_msg_copy( $dst, $src )

Copies contents of $src to $dst. 📋

Returns a non-zero status upon failure, and sets $!.

zmq_msg_move( $dst, $src )

Moves contents of $src to $dst 🚚

Returns a non-zero status upon failure, and sets $!.

$rv = zmq_msg_close( $msg )

Closes, cleans up the message. 🧹

Returns a non-zero status upon failure, and sets $!.

$rv = zmq_poll( \@pollitems, $timeout )

@pollitems are list of hash references containing the following elements:

• fd or socket — One of either "fd" or "socket" key must exist. "fd" should contain a UNIX file descriptor. "socket" should contain a ZMQ::LibZMQ4::Socket socket object. 🔌
• events — A bit mask containing ZMQ_POLLOUT, ZMQ_POLLIN, ZMQ_POLLERR or combination there of. 🎛️
• callback — A subroutine reference, which will be called without arguments when the socket or descriptor is available. 📞

In scalar context, returns the return value of zmq_poll() in the C layer, and sets $!.

my $rv = zmq_poll( .... ); # do scalar(zmq_poll(...)) if you're nuerotic
if ( $rv == -1 ) {
    warn "zmq_poll failed: $!";
}

In list context, return a list containing as many booleans as there are elements in @pollitems. These booleans indicate whether the socket in question has fired the callback.

my @pollitems = (...);
my @fired     = zmq_poll( @pollitems ... );
for my $i ( 0 .. $#pollitems ) {
    my $fired = $fired[$i];
    if ( $fired ) {
        my $item = $pollitems[$i];
        ...
    }
}

zmq_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 $version_string = ZMQ::LibZMQ4::zmq_version();
my ($major, $minor, $patch) = ZMQ::LibZMQ4::zmq_version();

zmq_device($type, $sock1, $sock2)

Creates a new "device". See "zmq_device" for details. zmq_device() will only return if/when the current context is closed. Therefore, the return value is always -1, and $! is always ETERM. 🎭

Note: may not be available depending on your libzmq version.

zmq_proxy($frontend_sock, $backend_sock, $capture_sock)

WARNING: EXPERIMENTAL. Use at your own risk. 💀

Start a proxy in the current thread, which connects the frontend socket to a backend socket. The capture sock is optional, and is by default undef. 🔀

Note: may not be available depending on your libzmq version.

$rv = zmq_socket_monitor($socket, $addr, events)

Note: may not be available depending on your libzmq version. 👀

✨ FUNCTIONS PROVIDED BY ZMQ::LIBZMQ4 ✨

okay bestie, listen up 💖 these functions are provided by ZMQ::LibZMQ4 to make some operations easier in the Perl binding. They are not part of the official libzmq interface, so don't go hunting for them in the C docs, mkay? 💅

$value = zmq_getsockopt_int( $sock, $option )
$value = zmq_getsockopt_int64( $sock, $option )
$value = zmq_getsockopt_string( $sock, $option )
$value = zmq_getsockopt_uint64( $sock, $option )
$rv = zmq_setsockopt_int( $sock, $option, $value );
$rv = zmq_setsockopt_int64( $sock, $option, $value );
$rv = zmq_setsockopt_string( $sock, $option, $value );
$rv = zmq_setsockopt_uint64( $sock, $option, $value );

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💀 DEBUGGING XS 💀

If you see segmentation faults, and such, you need to figure out where the error is occurring in order for the maintainers to figure out what happened. Here's a very very brief explanation of steps involved. no cap, this is the vibe check for crashes 🫶

First, make sure to compile "ZMQ::LibZMQ4" with debugging on by specifying -g:

perl Makefile.PL -g
make

Then fire gdb:

gdb perl
(gdb) R -Mblib /path/to/your/script.pl

When you see the crash, get a backtrace:

(gdb) bt

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😭 CAVEATS 😭

This is an early release. Proceed with caution, please report (or better yet: fix) bugs you encounter. be careful, bestie 🙈

This module has been tested against zeromq 3.2.2. Semantics of this module rely heavily on the underlying zeromq version. Make sure you know which version of zeromq you're working with. fr fr, version matters 👑

As of 1.04 some new constants have been added, but they are not really meant to be used by consumers of this module. If you find yourself looking at these, please let us know why you need to use it -- we'll see if we can find a workaround, or make these constants public. iykyk ✨

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🌈 SEE ALSO 🌈

• <http://zeromq.org>
• <http://github.com/mosconi/p5-ZMQ>
• <http://github.com/lestrrat/p5-ZMQ>
• ZMQ::Constants
• ZMQ::LibZMQ3
• ZMQ::LibZMQ2

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🎀 AUTHOR 🎀

Rodrigo Mosconi "<perl@mosconi.mat.br>"

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💜 COPYRIGHT AND LICENSE 💜

The ZMQ::LibZMQ4 module is

Copyright (C) 2014 by Rodrigo Mosconi

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.

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this page is from ZMQ::LibZMQ4(3), running on perl v5.42.0, dated 2025-07-25 💖 slay, go write some sockets bestie 🦋