zmq_proxy - start built-in 0MQ proxy
int zmq_proxy (const void *frontend, const void
*backend, const void *capture);
function starts the built-in 0MQ proxy in the current
The proxy 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. The direction is conceptual only; the proxy is
fully symmetric and there is no technical difference between frontend and
Before calling zmq_proxy()
you must set any socket options, and connect
or bind both frontend and backend sockets. The two conventional proxy models
runs in the current thread and returns only if/when the
current context is closed.
If the capture socket is not NULL, the proxy shall send all messages, received
on both frontend and backend, to the capture socket. The capture socket should
be a ZMQ_PUB
, or ZMQ_PAIR
Refer to zmq_socket
(3) for a description of the available socket types.
When the frontend is a ZMQ_ROUTER socket, and the backend is a ZMQ_DEALER
socket, the proxy shall act as a shared queue that collects requests from a
set of clients, and distributes these fairly among a set of services. Requests
shall be fair-queued from frontend connections and distributed evenly across
backend connections. Replies shall automatically return to the client that
made the original request.
When the frontend is a ZMQ_XSUB socket, and the backend is a ZMQ_XPUB socket,
the proxy shall act as a message forwarder that collects messages from a set
of publishers and forwards these to a set of subscribers. This may be used to
bridge networks transports, e.g. read on tcp:// and forward on pgm://.
When the frontend is a ZMQ_PULL socket, and the backend is a ZMQ_PUSH socket,
the proxy shall collect tasks from a set of clients and forwards these to a
set of workers using the pipeline pattern.
function always returns -1 and errno
(the 0MQ context
associated with either of
the specified sockets was terminated).
Creating a shared queue proxy
// Create frontend and backend sockets
void *frontend = zmq_socket (context, ZMQ_ROUTER);
void *backend = zmq_socket (context, ZMQ_DEALER);
// Bind both sockets to TCP ports
assert (zmq_bind (frontend, "tcp://*:5555") == 0);
assert (zmq_bind (backend, "tcp://*:5556") == 0);
// Start the queue proxy, which runs until ETERM
zmq_proxy (frontend, backend, NULL);
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