zmq_proxy_steerable.txt

zmq_proxy_steerable(3)
======================

NAME
----
zmq_proxy_steerable - built-in 0MQ proxy with control flow


SYNOPSIS
--------
*int zmq_proxy_steerable (const void '*frontend', const void '*backend', 
     const void '*capture', const void '*control');*


DESCRIPTION
-----------
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.


Refer to linkzmq:zmq_socket[3] for a description of the available socket types.
Refer to linkzmq:zmq_proxy[3] for a description of the zmq_proxy.

EXAMPLE USAGE
-------------
cf zmq_proxy

RETURN VALUE
------------
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).


EXAMPLE
-------
.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
--------
linkzmq:zmq_proxy[3]
linkzmq:zmq_bind[3]
linkzmq:zmq_connect[3]
linkzmq:zmq_socket[3]
linkzmq:zmq[7]


AUTHORS
-------
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