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122 lines
3.6 KiB
Plaintext
122 lines
3.6 KiB
Plaintext
= zmq_proxy_steerable(3)
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== NAME
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zmq_proxy_steerable - built-in 0MQ proxy with control flow
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== SYNOPSIS
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*int zmq_proxy_steerable (const void '*frontend', const void '*backend',
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const void '*capture', const void '*control');*
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== DESCRIPTION
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The _zmq_proxy_steerable()_ function is a variant of the _zmq_proxy()_ function.
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It accepts a fourth _control_ socket. When the _control_ socket is _NULL_ the
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two functions operate identically.
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When a _control_ socket of type _REP_ or _PAIR_ is provided to the proxy function the
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application may send commands to the proxy. The following commands are
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supported.
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_PAUSE_::
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The proxy will cease transferring messages between its endpoints. _REP_ control socket will reply with an empty message. No response otherwise.
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_RESUME_::
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The proxy will resume transferring messages between its endpoints. _REP_ control socket will reply with an empty message. No response otherwise.
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_TERMINATE_::
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The proxy function will exit with a return value of 0. _REP_ control socket will reply with an empty message. No response otherwise.
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_STATISTICS_::
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The proxy state will remain unchanged and reply with a set of simple summary values of the messages that have been sent through the proxy as described next. Control socket must support sending.
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There are eight statistics values, each of size _uint64_t_ in the multi-part
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message reply to the _STATISTICS_ command. These are:
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- number of messages received by the frontend socket
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- number of bytes received by the frontend socket
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- number of messages sent by the frontend socket
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- number of bytes sent by the frontend socket
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- number of messages received by the backend socket
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- number of bytes received by the backend socket
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- number of messages sent by the backend socket
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- number of bytes sent by the backend socket
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Message totals count each part in a multipart message individually.
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== RETURN VALUE
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The _zmq_proxy_steerable()_ function returns 0 if TERMINATE is received on its
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control socket. Otherwise, it returns -1 and errno set to ETERM or EINTR (the
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0MQ context associated with either of the specified sockets was terminated) or
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EFAULT (the provided frontend or backend was invalid).
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== EXAMPLE
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.Create a function to run the proxy
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----
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// Create the frontend and backend sockets to be proxied
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void *frontend = zmq_socket (context, ZMQ_ROUTER);
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void *backend = zmq_socket (context, ZMQ_DEALER);
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// Create the proxy control socket
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void *control = zmq_socket (context, ZMQ_REP);
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// Bind the sockets.
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zmq_bind (frontend, "tcp://*:5555");
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zmq_bind (backend, "tcp://*:5556");
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zmq_bind (control, "tcp://*:5557");
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zmq_proxy_steerable(frontend, backend, NULL, control);
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----
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.Code in another thread/process to steer the proxy.
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----
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void *control = zmq_socket (context, ZMQ_REQ);
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zmq_connect (control, "tcp://*:5557");
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zmq_msg_t msg;
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zmq_send (control, "PAUSE", 5, 0);
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zmq_msg_recv (&msg, control, 0));
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zmq_send (control, "RESUME", 6, 0);
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zmq_msg_recv (&msg, control, 0));
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zmq_send (control, "STATISTICS", 10, 0);
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while (1) {
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zmq_msg_recv (&msg, control, 0));
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printf(" %lu", *(uint64_t *)zmq_msg_data (&msg));
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if (!zmq_msg_get (&msg, ZMQ_MORE))
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break;
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}
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printf("\n");
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zmq_send (control, "TERMINATE", 9, 0);
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zmq_msg_recv (&msg, control, 0));
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zmq_close(frontend);
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zmq_close(backend);
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zmq_close(control);
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----
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== SEE ALSO
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* xref:zmq_proxy.adoc[zmq_proxy]
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* xref:zmq_bind.adoc[zmq_bind]
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* xref:zmq_connect.adoc[zmq_connect]
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* xref:zmq_socket.adoc[zmq_socket]
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* xref:zmq.adoc[zmq]
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== AUTHORS
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This page was written by the 0MQ community. To make a change please
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read the 0MQ Contribution Policy at <https://zeromq.org/how-to-contribute/>.
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