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
       Before using any 0MQ library functions the caller must initialise a 0MQ context using zmq_init(). The following functions are provided to
       handle initialisation and termination of a context:

       Initialise 0MQ context

	   zmq_init(3)

       Terminate 0MQ context

	   zmq_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 initialization, 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_data(3)

       Release a message

	   zmq_msg_close(3)

       Access message content

	   zmq_msg_data(3) zmq_msg_size(3)

       Message manipulation

	   zmq_msg_copy(3) zmq_msg_move(3)

   Sockets
       0MQ sockets present an abstraction of a 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_send(3) zmq_recv(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).

   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)

   Devices
       0MQ provides devices, which are building blocks that act as intermediate nodes in complex messaging topologies. Devices can act as brokers
       that other nodes connect to, proxies that connect through to other nodes, or any mix of these two models.

       You can start a device in an application thread, see zmq_device(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).

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.

   C++ language binding
       The 0MQ distribution includes a C++ language binding, which is documented separately in zmq_cpp(7).

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

AUTHORS

       This manual page was written by the 0MQ community.

RESOURCES

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

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

COPYING

       Free use of this software is granted under the terms of the GNU Lesser General Public License (LGPL). For details see the files COPYING and
       COPYING.LESSER included with the 0MQ distribution.

NOTES

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

0MQ 2.2.0							    04/04/2012								    ZMQ(7)