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260 lines
7.4 KiB
Plaintext
260 lines
7.4 KiB
Plaintext
zmq_ctx_socket_monitor(3)
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=========================
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NAME
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----
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zmq_socket_monitor - register a monitoring callback
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SYNOPSIS
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--------
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*int zmq_socket_monitor (void '*socket', char * '*addr', int 'events');*
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DESCRIPTION
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-----------
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The _zmq_socket_monitor()_ function shall spawn a 'PAIR' socket that publishes
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socket state changes (events) over the inproc:// transport to a given endpoint.
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Messages consist of 2 Frames, the first containing the event-id and the
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associated value. The second frame holds the affected endpoint as string.
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The layout of the first Frame is:
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16 bit event id
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32 bit event value
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event id and value are in the native byte order (for the machine the
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application is running on). There is no padding between the fields.
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The event value has to be interpreted in the context of the event id.
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See 'Supported events' below for details.
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----
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Only connection oriented (tcp and ipc) transports are supported in this initial
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implementation.
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----
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Supported events
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----------------
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ZMQ_EVENT_CONNECTED: connection established
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_CONNECTED' event triggers when a connection has been established
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to a remote peer. This can happen either synchronous or asynchronous.
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Value is the FD of the newly connected socket.
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ZMQ_EVENT_CONNECT_DELAYED: synchronous connect failed, it's being polled
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_CONNECT_DELAYED' event triggers when an immediate connection
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attempt is delayed and its completion is being polled for.
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Value has no meaning.
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ZMQ_EVENT_CONNECT_RETRIED: asynchronous connect / reconnection attempt
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_CONNECT_RETRIED' event triggers when a connection attempt
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is being handled by reconnect timer. The reconnect interval's recomputed
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for each attempt.
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Value is the reconnect interval.
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ZMQ_EVENT_LISTENING: socket bound to an address, ready to accept connections
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_LISTENING' event triggers when a socket's successfully bound
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to a an interface.
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Value is the FD of the newly bound socket.
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ZMQ_EVENT_BIND_FAILED: socket could not bind to an address
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_BIND_FAILED' event triggers when a socket could not bind to
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a given interface.
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Value is the errno generated by the bind call.
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ZMQ_EVENT_ACCEPTED: connection accepted to bound interface
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_ACCEPTED' event triggers when a connection from a remote peer
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has been established with a socket's listen address.
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Value is the FD of the accepted socket.
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ZMQ_EVENT_ACCEPT_FAILED: could not accept client connection
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_ACCEPT_FAILED' event triggers when a connection attempt to
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a socket's bound address fails.
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Value is the errno generated by accept.
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ZMQ_EVENT_CLOSED: connection closed
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_CLOSED' event triggers when a connection's underlying descriptor
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has been closed.
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Value is the former FD of the for the closed socket. FD has been closed already!
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ZMQ_EVENT_CLOSE_FAILED: connection couldn't be closed
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_CLOSE_FAILED' event triggers when a descriptor could not be
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released back to the OS. Implementation note: ONLY FOR IPC SOCKETS.
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Value is the errno generated by unlink.
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ZMQ_EVENT_DISCONNECTED: broken session
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The 'ZMQ_EVENT_DISCONNECTED' event triggers when the stream engine (tcp and ipc
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specific) detects a corrupted / broken session.
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Value is the FD of the socket.
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RETURN VALUE
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------------
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The _zmq_socket_monitor()_ function returns a value of 0 or greater if
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successful. Otherwise it returns `-1` and sets 'errno' to one of the values
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defined below.
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ERRORS
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------
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*ETERM*::
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The 0MQ 'context' associated with the specified 'socket' was terminated.
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*EPROTONOSUPPORT*::
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The requested 'transport' protocol is not supported. Monitor sockets are
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required to use the inproc:// transport.
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*EINVAL*::
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The endpoint supplied is invalid.
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EXAMPLE
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-------
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.Observing a 'REP' socket's connection state
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----
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#include <stdio.h>
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#include <zmq.h>
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#include <pthread.h>
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#include <string.h>
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#include <assert.h>
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static int read_msg(void* s, zmq_event_t* event, char* ep)
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{
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int rc ;
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zmq_msg_t msg1; // binary part
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zmq_msg_init (&msg1);
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zmq_msg_t msg2; // address part
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zmq_msg_init (&msg2);
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rc = zmq_msg_recv (&msg1, s, 0);
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if (rc == -1 && zmq_errno() == ETERM)
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return 1 ;
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assert (rc != -1);
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assert (zmq_msg_more(&msg1) != 0);
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rc = zmq_msg_recv (&msg2, s, 0);
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if (rc == -1 && zmq_errno() == ETERM)
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return 1;
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assert (rc != -1);
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assert (zmq_msg_more(&msg2) == 0);
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// copy binary data to event struct
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const char* data = (char*)zmq_msg_data(&msg1);
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memcpy(&(event->event), data, sizeof(event->event));
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memcpy(&(event->value), data+sizeof(event->event), sizeof(event->value));
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// copy address part
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const size_t len = zmq_msg_size(&msg2) ;
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ep = memcpy(ep, zmq_msg_data(&msg2), len);
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*(ep + len) = 0 ;
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return 0 ;
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}
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// REP socket monitor thread
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static void *rep_socket_monitor (void *ctx)
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{
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zmq_event_t event;
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static char addr[1025] ;
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int rc;
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printf("starting monitor...\n");
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void *s = zmq_socket (ctx, ZMQ_PAIR);
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assert (s);
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rc = zmq_connect (s, "inproc://monitor.rep");
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assert (rc == 0);
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while (!read_msg(s, &event, addr)) {
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switch (event.event) {
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case ZMQ_EVENT_LISTENING:
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printf ("listening socket descriptor %d\n", event.value);
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printf ("listening socket address %s\n", addr);
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break;
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case ZMQ_EVENT_ACCEPTED:
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printf ("accepted socket descriptor %d\n", event.value);
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printf ("accepted socket address %s\n", addr);
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break;
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case ZMQ_EVENT_CLOSE_FAILED:
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printf ("socket close failure error code %d\n", event.value);
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printf ("socket address %s\n", addr);
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break;
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case ZMQ_EVENT_CLOSED:
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printf ("closed socket descriptor %d\n", event.value);
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printf ("closed socket address %s\n", addr);
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break;
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case ZMQ_EVENT_DISCONNECTED:
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printf ("disconnected socket descriptor %d\n", event.value);
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printf ("disconnected socket address %s\n", addr);
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break;
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}
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}
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zmq_close (s);
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return NULL;
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}
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int main()
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{
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const char* addr = "tcp://127.0.0.1:6666" ;
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pthread_t thread ;
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// Create the infrastructure
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void *ctx = zmq_init (1);
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assert (ctx);
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// REP socket
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void* rep = zmq_socket (ctx, ZMQ_REP);
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assert (rep);
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// REP socket monitor, all events
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int rc = zmq_socket_monitor (rep, "inproc://monitor.rep", ZMQ_EVENT_ALL);
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assert (rc == 0);
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rc = pthread_create (&thread, NULL, rep_socket_monitor, ctx);
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assert (rc == 0);
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rc = zmq_bind (rep, addr);
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assert (rc == 0);
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// Allow some time for event detection
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zmq_sleep (1);
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// Close the REP socket
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rc = zmq_close (rep);
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assert (rc == 0);
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zmq_term (ctx);
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return 0 ;
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}
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----
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SEE ALSO
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--------
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linkzmq:zmq[7]
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AUTHORS
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-------
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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 <http://www.zeromq.org/docs:contributing>.
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