DragonFly On-Line Manual Pages

ZMQ_DEVICE(3)                     0MQ Manual                     ZMQ_DEVICE(3)

NAME
       zmq_device - start built-in 0MQ device

SYNOPSIS
       int zmq_device (int device, const void *frontend, const void *backend);

DESCRIPTION
       The zmq_device() function starts a built-in 0MQ device. The device
       argument is one of:

       ZMQ_QUEUE
           starts a queue device

       ZMQ_FORWARDER
           starts a forwarder device

       ZMQ_STREAMER
           starts a streamer device

       The device connects a frontend socket to a backend socket.
       Conceptually, data flows from frontend to backend. Depending on the
       socket types, replies may flow in the opposite direction.

       Before calling zmq_device() you must set any socket options, and
       connect or bind both frontend and backend sockets. The two conventional
       device models are:

       proxy
           bind frontend socket to an endpoint, and connect backend socket to
           downstream components. A proxy device model does not require
           changes to the downstream topology but that topology is static (any
           changes require reconfiguring the device).

       broker
           bind frontend socket to one endpoint and bind backend socket to a
           second endpoint. Downstream components must now connect into the
           device. A broker device model allows a dynamic downstream topology
           (components can come and go at any time).

       zmq_device() runs in the current thread and returns only if/when the
       current context is closed.

QUEUE DEVICE
       ZMQ_QUEUE creates a shared queue that collects requests from a set of
       clients, and distributes these fairly among a set of services. Requests
       are fair-queued from frontend connections and load-balanced between
       backend connections. Replies automatically return to the client that
       made the original request.

       This device is part of the request-reply pattern. The frontend speaks
       to clients and the backend speaks to services. You should use ZMQ_QUEUE
       with a ZMQ_XREP socket for the frontend and a ZMQ_XREQ socket for the
       backend. Other combinations are not documented.

       Refer to zmq_socket(3) for a description of these socket types.

FORWARDER DEVICE
       ZMQ_FORWARDER collects messages from a set of publishers and forwards
       these to a set of subscribers. You will generally use this to bridge
       networks, e.g. read on TCP unicast and forward on multicast.

       This device is part of the publish-subscribe pattern. The frontend
       speaks to publishers and the backend speaks to subscribers. You should
       use ZMQ_FORWARDER with a ZMQ_SUB socket for the frontend and a ZMQ_PUB
       socket for the backend. Other combinations are not documented.

       Refer to zmq_socket(3) for a description of these socket types.

STREAMER DEVICE
       ZMQ_STREAMER collects tasks from a set of pushers and forwards these to
       a set of pullers. You will generally use this to bridge networks.
       Messages are fair-queued from pushers and load-balanced to pullers.

       This device is part of the pipeline pattern. The frontend speaks to
       pushers and the backend speaks to pullers. You should use ZMQ_STREAMER
       with a ZMQ_PULL socket for the frontend and a ZMQ_PUSH socket for the
       backend. Other combinations are not documented.

       Refer to zmq_socket(3) for a description of these socket types.

RETURN VALUE
       The zmq_device() function always returns -1 and errno set to ETERM (the
       0MQ context associated with either of the specified sockets was
       terminated).

EXAMPLE
       Creating a queue broker.

           //  Create frontend and backend sockets
           void *frontend = zmq_socket (context, ZMQ_XREP);
           assert (backend);
           void *backend = zmq_socket (context, ZMQ_XREQ);
           assert (frontend);
           //  Bind both sockets to TCP ports
           assert (zmq_bind (frontend, "tcp://*:5555") == 0);
           assert (zmq_bind (backend, "tcp://*:5556") == 0);
           //  Start a queue device
           zmq_device (ZMQ_QUEUE, frontend, backend);

SEE ALSO
       zmq_bind(3) zmq_connect(3) zmq_socket(3) zmq(7)

AUTHORS
       This manual page was written by the 0MQ community.

0MQ 2.2.0                         04/04/2012                     ZMQ_DEVICE(3)