ZMQ(7)				  0MQ Manual				ZMQ(7)

NAME
       zmq - 0MQ lightweight messaging kernel

SYNOPSIS
       #include <zmq.h>

       cc [flags] files -lzmq [libraries]

DESCRIPTION
       The 0MQ lightweight messaging kernel is a library which extends the
       standard socket interfaces with features traditionally provided by
       specialised messaging middleware products. 0MQ sockets provide an
       abstraction of asynchronous message queues, multiple messaging
       patterns, message filtering (subscriptions), seamless access to
       multiple transport protocols and more.

       This documentation presents an overview of 0MQ concepts, describes how
       0MQ abstracts standard sockets and provides a reference manual for the
       functions provided by the 0MQ library.

   Context
       The 0MQ context keeps the list of sockets and manages the async I/O
       thread and internal queries.

       Before using any 0MQ library functions you must create a 0MQ context.
       When you exit your application you must destroy the context. These
       functions let you work with contexts:

       Create a new 0MQ context
	   zmq_ctx_new(3)

       Work with context properties
	   zmq_ctx_set(3) zmq_ctx_get(3)

       Destroy a 0MQ context
	   zmq_ctx_shutdown(3) zmq_ctx_term(3)

       Thread safety

	   A 0MQ context is thread safe and may be shared among as many
	   application threads as necessary, without any additional locking
	   required on the part of the caller.

	   Individual 0MQ sockets are not thread safe except in the case where
	   full memory barriers are issued when migrating a socket from one
	   thread to another. In practice this means applications can create a
	   socket in one thread with zmq_socket() and then pass it to a newly
	   created thread as part of thread initialisation, for example via a
	   structure passed as an argument to pthread_create().

       Multiple contexts

	   Multiple contexts may coexist within a single application. Thus, an
	   application can use 0MQ directly and at the same time make use of
	   any number of additional libraries or components which themselves
	   make use of 0MQ as long as the above guidelines regarding thread
	   safety are adhered to.

   Messages
       A 0MQ message is a discrete unit of data passed between applications or
       components of the same application. 0MQ messages have no internal
       structure and from the point of view of 0MQ itself they are considered
       to be opaque binary data.

       The following functions are provided to work with messages:

       Initialise a message
	   zmq_msg_init(3) zmq_msg_init_size(3) zmq_msg_init_buffer(3)
	   zmq_msg_init_data(3)

       Sending and receiving a message
	   zmq_msg_send(3) zmq_msg_recv(3)

       Release a message
	   zmq_msg_close(3)

       Access message content
	   zmq_msg_data(3) zmq_msg_size(3) zmq_msg_more(3)

       Work with message properties
	   zmq_msg_gets(3) zmq_msg_get(3) zmq_msg_set(3)

       Message manipulation
	   zmq_msg_copy(3) zmq_msg_move(3)

   Sockets
       0MQ sockets present an abstraction of an asynchronous message queue,
       with the exact queueing semantics depending on the socket type in use.
       See zmq_socket(3) for the socket types provided.

       The following functions are provided to work with sockets:

       Creating a socket
	   zmq_socket(3)

       Closing a socket
	   zmq_close(3)

       Manipulating socket options
	   zmq_getsockopt(3) zmq_setsockopt(3)

       Establishing a message flow
	   zmq_bind(3) zmq_connect(3)

       Sending and receiving messages
	   zmq_msg_send(3) zmq_msg_recv(3) zmq_send(3) zmq_recv(3)
	   zmq_send_const(3)

       Monitoring socket events
	   zmq_socket_monitor(3)

       Input/output multiplexing. 0MQ provides a mechanism for applications to
       multiplex input/output events over a set containing both 0MQ sockets
       and standard sockets. This mechanism mirrors the standard poll() system
       call, and is described in detail in zmq_poll(3). This API is
       deprecated, however.

       There is a new DRAFT API with multiple zmq_poller_* function, which is
       described in zmq_poller(3).

   Transports
       A 0MQ socket can use multiple different underlying transport
       mechanisms. Each transport mechanism is suited to a particular purpose
       and has its own advantages and drawbacks.

       The following transport mechanisms are provided:

       Unicast transport using TCP
	   zmq_tcp(7)

       Reliable multicast transport using PGM
	   zmq_pgm(7)

       Local inter-process communication transport
	   zmq_ipc(7)

       Local in-process (inter-thread) communication transport
	   zmq_inproc(7)

       Virtual Machine Communications Interface (VMC) transport
	   zmq_vmci(7)

       Unreliable unicast and multicast using UDP
	   zmq_udp(7)

   Proxies
       0MQ provides proxies to create fanout and fan-in topologies. A proxy
       connects a frontend socket to a backend socket and switches all
       messages between the two sockets, opaquely. A proxy may optionally
       capture all traffic to a third socket. To start a proxy in an
       application thread, use zmq_proxy(3).

   Security
       A 0MQ socket can select a security mechanism. Both peers must use the
       same security mechanism.

       The following security mechanisms are provided for IPC and TCP
       connections:

       Null security
	   zmq_null(7)

       Plain-text authentication using username and password
	   zmq_plain(7)

       Elliptic curve authentication and encryption
	   zmq_curve(7)

       Generate a CURVE keypair in armored text format
	   zmq_curve_keypair(3)

       Derive a CURVE public key from a secret key: zmq_curve_public(3)

       Converting keys to/from armoured text strings
	   zmq_z85_decode(3) zmq_z85_encode(3)

ERROR HANDLING
       The 0MQ library functions handle errors using the standard conventions
       found on POSIX systems. Generally, this means that upon failure a 0MQ
       library function shall return either a NULL value (if returning a
       pointer) or a negative value (if returning an integer), and the actual
       error code shall be stored in the errno variable.

       On non-POSIX systems some users may experience issues with retrieving
       the correct value of the errno variable. The zmq_errno() function is
       provided to assist in these cases; for details refer to zmq_errno(3).

       The zmq_strerror() function is provided to translate 0MQ-specific error
       codes into error message strings; for details refer to zmq_strerror(3).

UTILITY
       The following utility functions are provided:

       Working with atomic counters
	   zmq_atomic_counter_new(3) zmq_atomic_counter_set(3)
	   zmq_atomic_counter_inc(3) zmq_atomic_counter_dec(3)
	   zmq_atomic_counter_value(3) zmq_atomic_counter_destroy(3)

MISCELLANEOUS
       The following miscellaneous functions are provided:

       Report 0MQ library version
	   zmq_version(3)

LANGUAGE BINDINGS
       The 0MQ library provides interfaces suitable for calling from programs
       in any language; this documentation documents those interfaces as they
       would be used by C programmers. The intent is that programmers using
       0MQ from other languages shall refer to this documentation alongside
       any documentation provided by the vendor of their language binding.

       Language bindings (C++, Python, PHP, Ruby, Java and more) are provided
       by members of the 0MQ community and pointers can be found on the 0MQ
       website.

AUTHORS
       This page was written by the 0MQ community. To make a change please
       read the 0MQ Contribution Policy at
       http://www.zeromq.org/docs:contributing.

RESOURCES
       Main web site: http://www.zeromq.org/

       Report bugs to the 0MQ development mailing list:
       <zeromq-dev@lists.zeromq.org[1]>

LICENSE
       Free use of this software is granted under the terms of the Mozilla
       Public License Version 2.0 (MPL-2.0). For details see the file LICENSE
       included with the 0MQ distribution.

NOTES
	1. zeromq-dev@lists.zeromq.org
	   mailto:zeromq-dev@lists.zeromq.org

0MQ 4.3.5			  10/23/2023				ZMQ(7)