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ZMQ_DEVICE(3) | 0MQ Manual | ZMQ_DEVICE(3) |
NAME¶
zmq_device - start built-in 0MQ deviceSYNOPSIS¶
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_QUEUEstarts 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.04/04/2012 | 0MQ 2.2.0 |