int zmq_proxy_steerable (const void *frontend, const void *backend, const void *capture, const void *control);
The zmq_proxy_steerable() function starts the built-in 0MQ proxy in the current application thread, as zmq_proxy() do. Please, refer to this function for the general description and usage. We describe here only the additional control flow provided by the socket passed as the fourth argument "control".
If the control socket is not NULL, the proxy supports control flow. If PAUSE is received on this socket, the proxy suspends its activities. If RESUME is received, it goes on. If TERMINATE is received, it terminates smoothly. At start, the proxy runs normally as if zmq_proxy was used.
If the control socket is NULL, the function behave exactly as if zmq_proxy had been called.
The zmq_proxy_steerable() function returns 0 if TERMINATE is sent to its control socket. Otherwise, it returns -1 and errno set to ETERM (the 0MQ context associated with either of the specified sockets was terminated).
Creating a shared queue proxy.
// Create frontend, backend and control sockets void *frontend = zmq_socket (context, ZMQ_ROUTER); assert (backend); void *backend = zmq_socket (context, ZMQ_DEALER); assert (frontend); void *control = zmq_socket (context, ZMQ_SUB); assert (control); // Bind sockets to TCP ports assert (zmq_bind (frontend, "tcp://*:5555") == 0); assert (zmq_bind (backend, "tcp://*:5556") == 0); assert (zmq_connect (control, "tcp://*:5557") == 0); // Subscribe to the control socket since we have chosen SUB here assert (zmq_setsockopt (control, ZMQ_SUBSCRIBE, "", 0)); // Start the queue proxy, which runs until ETERM or "TERMINATE" // received on the control socket zmq_proxy_steerable (frontend, backend, NULL, control);
Set up a controller in another node, process or whatever.
void *control = zmq_socket (context, ZMQ_PUB); assert (control); assert (zmq_bind (control, "tcp://*:5557") == 0); // pause the proxy assert (zmq_send (control, "PAUSE", 5, 0) == 0); // resume the proxy assert (zmq_send (control, "RESUME", 6, 0) == 0); // terminate the proxy assert (zmq_send (control, "TERMINATE", 9, 0) == 0); --- SEE ALSO
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