zmq_proxy - start built-in 0MQ proxy

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0MQ 4.3.5                                          03/31/2024                                       ZMQ_PROXY(3)

       The zmq_proxy() function starts the built-in 0MQ proxy in the current application thread.

       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
       backend.

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

       zmq_proxy() 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, ZMQ_DEALER, ZMQ_PUSH, or ZMQ_PAIR
       socket.

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

Creatingasharedqueueproxy.

           //  Create frontend and backend sockets
           void *frontend = zmq_socket (context, ZMQ_ROUTER);
           assert (frontend);
           void *backend = zmq_socket (context, ZMQ_DEALER);
           assert (backend);
           //  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);

SharedQueue
       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.

   Forwarder
       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://.Streamer
       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.

       zmq_proxy - start built-in 0MQ proxy

       The zmq_proxy() function always returns -1 and errno set to ETERM or EINTR (the 0MQ context associated
       with either of the specified sockets was terminated) or EFAULT (the provided frontend or backend was
       invalid).

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

intzmq_proxy(void*frontend,void*backend,void*capture);