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       zmq - 0MQ lightweight messaging kernel


       #include <zmq.h>

       cc [flags] files -lzmq [libraries]


       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.

       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


       Terminate 0MQ context


       Thread safety
           A 0MQ context is thread safe and may be shared among as many
           application threads as the application has requested using the
           app_threads parameter to zmq_init(), without any additional locking
           required on the part of the caller. Each 0MQ socket belonging to a
           particular context may only be used by the thread that created it
           using zmq_socket().

       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.

       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


       Access message content

           zmq_msg_data(3) zmq_msg_size(3)

       Message manipulation

           zmq_msg_copy(3) zmq_msg_move(3)

       Standard sockets present a synchronous interface to either
       connection-mode reliable byte streams (SOCK_STREAM), or connection-less
       unreliable datagrams (SOCK_DGRAM). In comparison, 0MQ sockets present
       an abstraction of a asynchronous message queue, with the exact queueing
       semantics depending on the socket type (messaging pattern) in use. See
       zmq_socket(3) for the messaging patterns provided.

       0MQ sockets being asynchronous means that the timings of the physical
       connection setup and teardown, reconnect and effective delivery are
       organized by 0MQ itself, and that messages may be queued in the event
       that a peer is unavailable to receive them.

       The following functions are provided to work with sockets:

       Creating a socket


       Closing a socket


       Setting socket options


       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).

       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


       Reliable multicast transport using PGM


       Local inter-process communication transport


       Local in-process (inter-thread) communication transport


       Apart from the 0MQ library the 0MQ distribution includes devices which
       are building blocks intended to serve as intermediate nodes in complex
       messaging topologies.

       The following devices are provided:

       Forwarder device for request-response messaging


       Forwarder device for publish-subscribe messaging


       Streamer device for parallelized pipeline messaging



       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.

       A zmq_strerror() function is provided to translate 0MQ-specific error
       codes into error message strings. For further details refer to


       The following miscellaneous functions are provided:

       Report 0MQ library version



       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


       The 0MQ documentation was written by Martin Sustrik
       <[1]> and Martin Lucina <[2]>.


       Main web site:

       Report bugs to the 0MQ development mailing list:


       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.