Provided by: libczmq-dev_4.1.0-2_amd64 
NAME
zbeacon - Class for LAN discovery and presence
SYNOPSIS
// Create new zbeacon actor instance:
//
// zactor_t *beacon = zactor_new (zbeacon, NULL);
//
// Destroy zbeacon instance:
//
// zactor_destroy (&beacon);
//
// Enable verbose logging of commands and activity:
//
// zstr_send (beacon, "VERBOSE");
//
// Configure beacon to run on specified UDP port, and return the name of
// the host, which can be used as endpoint for incoming connections. To
// force the beacon to operate on a given interface, set the environment
// variable ZSYS_INTERFACE, or call zsys_set_interface() before creating
// the beacon. If the system does not support UDP broadcasts (lacking a
// workable interface), returns an empty hostname:
//
// // Pictures: 's' = C string, 'i' = int
// zsock_send (beacon, "si", "CONFIGURE", port_number);
// char *hostname = zstr_recv (beacon);
//
// Start broadcasting a beacon at a specified interval in msec. The beacon
// data can be at most UDP_FRAME_MAX bytes; this constant is defined in
// zsys.h to be 255:
//
// // Pictures: 'b' = byte * data + size_t size
// zsock_send (beacon, "sbi", "PUBLISH", data, size, interval);
//
// Stop broadcasting the beacon:
//
// zstr_sendx (beacon, "SILENCE", NULL);
//
// Start listening to beacons from peers. The filter is used to do a prefix
// match on received beacons, to remove junk. Note that any received data
// that is identical to our broadcast beacon_data is discarded in any case.
// If the filter size is zero, we get all peer beacons:
//
// zsock_send (beacon, "sb", "SUBSCRIBE", filter_data, filter_size);
//
// Stop listening to other peers
//
// zstr_sendx (beacon, "UNSUBSCRIBE", NULL);
//
// Receive next beacon from a peer. Received beacons are always a 2-frame
// message containing the ipaddress of the sender, and then the binary
// beacon data as published by the sender:
//
// zmsg_t *msg = zmsg_recv (beacon);
//
// This is the zbeacon constructor as a zactor_fn:
CZMQ_EXPORT void
zbeacon (zsock_t *pipe, void *unused);
// Self test of this class
CZMQ_EXPORT void
zbeacon_test (bool verbose);
Please add '@interface' section in './../src/zbeacon.c'.
DESCRIPTION
The zbeacon class implements a peer-to-peer discovery service for local networks. A beacon
can broadcast and/or capture service announcements using UDP messages on the local area
network. This implementation uses IPv4 UDP broadcasts. You can define the format of your
outgoing beacons, and set a filter that validates incoming beacons. Beacons are sent and
received asynchronously in the background.
This class replaces zbeacon_v2, and is meant for applications that use the CZMQ v3 API
(meaning, zsock).
EXAMPLE
From zbeacon_test method.
// Test 1 - two beacons, one speaking, one listening
// Create speaker beacon to broadcast our service
zactor_t *speaker = zactor_new (zbeacon, NULL);
assert (speaker);
if (verbose)
zstr_sendx (speaker, "VERBOSE", NULL);
zsock_send (speaker, "si", "CONFIGURE", 9999);
char *hostname = zstr_recv (speaker);
if (!*hostname) {
printf ("OK (skipping test, no UDP broadcasting)\n");
zactor_destroy (&speaker);
freen (hostname);
return;
}
freen (hostname);
// Create listener beacon on port 9999 to lookup service
zactor_t *listener = zactor_new (zbeacon, NULL);
assert (listener);
if (verbose)
zstr_sendx (listener, "VERBOSE", NULL);
zsock_send (listener, "si", "CONFIGURE", 9999);
hostname = zstr_recv (listener);
assert (*hostname);
freen (hostname);
// We will broadcast the magic value 0xCAFE
byte announcement [2] = { 0xCA, 0xFE };
zsock_send (speaker, "sbi", "PUBLISH", announcement, 2, 100);
// We will listen to anything (empty subscription)
zsock_send (listener, "sb", "SUBSCRIBE", "", 0);
// Wait for at most 1/2 second if there's no broadcasting
zsock_set_rcvtimeo (listener, 500);
char *ipaddress = zstr_recv (listener);
if (ipaddress) {
zframe_t *content = zframe_recv (listener);
assert (zframe_size (content) == 2);
assert (zframe_data (content) [0] == 0xCA);
assert (zframe_data (content) [1] == 0xFE);
zframe_destroy (&content);
zstr_free (&ipaddress);
zstr_sendx (speaker, "SILENCE", NULL);
}
zactor_destroy (&listener);
zactor_destroy (&speaker);
// Test subscription filter using a 3-node setup
zactor_t *node1 = zactor_new (zbeacon, NULL);
assert (node1);
zsock_send (node1, "si", "CONFIGURE", 5670);
hostname = zstr_recv (node1);
assert (*hostname);
freen (hostname);
zactor_t *node2 = zactor_new (zbeacon, NULL);
assert (node2);
zsock_send (node2, "si", "CONFIGURE", 5670);
hostname = zstr_recv (node2);
assert (*hostname);
freen (hostname);
zactor_t *node3 = zactor_new (zbeacon, NULL);
assert (node3);
zsock_send (node3, "si", "CONFIGURE", 5670);
hostname = zstr_recv (node3);
assert (*hostname);
freen (hostname);
zsock_send (node1, "sbi", "PUBLISH", "NODE/1", 6, 250);
zsock_send (node2, "sbi", "PUBLISH", "NODE/2", 6, 250);
zsock_send (node3, "sbi", "PUBLISH", "RANDOM", 6, 250);
zsock_send (node1, "sb", "SUBSCRIBE", "NODE", 4);
// Poll on three API sockets at once
zpoller_t *poller = zpoller_new (node1, node2, node3, NULL);
assert (poller);
int64_t stop_at = zclock_mono () + 1000;
while (zclock_mono () < stop_at) {
long timeout = (long) (stop_at - zclock_mono ());
if (timeout < 0)
timeout = 0;
void *which = zpoller_wait (poller, timeout * ZMQ_POLL_MSEC);
if (which) {
assert (which == node1);
char *ipaddress, *received;
zstr_recvx (node1, &ipaddress, &received, NULL);
assert (streq (received, "NODE/2"));
zstr_free (&ipaddress);
zstr_free (&received);
}
}
zpoller_destroy (&poller);
// Stop listening
zstr_sendx (node1, "UNSUBSCRIBE", NULL);
// Stop all node broadcasts
zstr_sendx (node1, "SILENCE", NULL);
zstr_sendx (node2, "SILENCE", NULL);
zstr_sendx (node3, "SILENCE", NULL);
// Destroy the test nodes
zactor_destroy (&node1);
zactor_destroy (&node2);
zactor_destroy (&node3);
#if defined (__WINDOWS__)
zsys_shutdown();
#endif
AUTHORS
The czmq manual was written by the authors in the AUTHORS file.
RESOURCES
Main web site:
Report bugs to the email <zeromq-dev@lists.zeromq.org[1]>
COPYRIGHT
Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ,
the high-level C binding for 0MQ: http://czmq.zeromq.org. This Source Code Form is subject
to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not
distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE
included with the czmq distribution.
NOTES
1. zeromq-dev@lists.zeromq.org
mailto:zeromq-dev@lists.zeromq.org