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Man Pages

Manual Reference Pages  -  ZBEACON_V2 (3)

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zbeacon_v2 - LAN discovery and presence (deprecated)



//  Create a new beacon on a certain UDP port. If the system does not
//  support UDP broadcasts (lacking a useful interface), returns NULL.
//  To force the beacon to operate on a given port, set the environment
//  variable ZSYS_INTERFACE, or call zsys_set_interface() beforehand.
//  If you are using the new zsock API then pass NULL as the ctx here.
CZMQ_EXPORT zbeacon_t *
    zbeacon_new (zctx_t *ctx, int port_nbr);

// Destroy a beacon CZMQ_EXPORT void zbeacon_destroy (zbeacon_t **self_p);

// Return our own IP address as printable string CZMQ_EXPORT char * zbeacon_hostname (zbeacon_t *self);

// Set broadcast interval in milliseconds (default is 1000 msec) CZMQ_EXPORT void zbeacon_set_interval (zbeacon_t *self, int interval);

// Filter out any beacon that looks exactly like ours CZMQ_EXPORT void zbeacon_noecho (zbeacon_t *self);

// Start broadcasting beacon to peers at the specified interval CZMQ_EXPORT void zbeacon_publish (zbeacon_t *self, byte *transmit, size_t size);

// Stop broadcasting beacons CZMQ_EXPORT void zbeacon_silence (zbeacon_t *self);

// Start listening to other peers; zero-sized filter means get everything CZMQ_EXPORT void zbeacon_subscribe (zbeacon_t *self, byte *filter, size_t size);

// Stop listening to other peers CZMQ_EXPORT void zbeacon_unsubscribe (zbeacon_t *self);

// Get beacon ZeroMQ socket, for polling or receiving messages CZMQ_EXPORT void * zbeacon_socket (zbeacon_t *self);

// Self test of this class CZMQ_EXPORT void zbeacon_v2_test (bool verbose);


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. The zbeacon API provides a incoming beacons on a ZeroMQ socket (the pipe) that you can configure, poll on, and receive messages on. Incoming beacons are always delivered as two frames: the ipaddress of the sender (a string), and the beacon data itself (binary, as published).

This class is deprecated in CZMQ v3; it works together with zctx, zsocket, and other deprecated V2 classes. New applications should use the V3 zauth interface, based on zactor, together with the zsock class for sockets.


From zbeacon_v2_test method.

//  Create beacon to broadcast our service
zctx_t *ctx = zctx_new ();
assert (ctx);
zbeacon_t *service_beacon = zbeacon_new (ctx, 9999);
if (service_beacon == NULL) {
    printf ("OK (skipping test, no UDP discovery)\n");
//  Create a service socket and bind to an ephemeral port
zsock_t *service = zsock_new (ZMQ_PUB);
assert (service);
int port_nbr = zsock_bind (service, "tcp://*");
byte announcement [2] = { (port_nbr >> 8) & 0xFF, port_nbr & 0xFF };
zbeacon_set_interval (service_beacon, 100);
zbeacon_publish (service_beacon, announcement, 2);

// Create beacon to lookup service zbeacon_t *client_beacon = zbeacon_new (ctx, 9999); assert (client_beacon); zbeacon_subscribe (client_beacon, NULL, 0);

// Wait for at most 1/2 second if theres no broadcast networking zsocket_set_rcvtimeo (zbeacon_socket (client_beacon), 500);

char *ipaddress = zstr_recv (zbeacon_socket (client_beacon)); if (ipaddress) { zframe_t *content = zframe_recv (zbeacon_socket (client_beacon)); int received_port = (zframe_data (content) [0] << 8) + zframe_data (content) [1]; assert (received_port == port_nbr); zframe_destroy (&content); zbeacon_silence (service_beacon); zstr_free (&ipaddress); } zbeacon_destroy (&client_beacon); zbeacon_destroy (&service_beacon);

zbeacon_t *node1 = zbeacon_new (ctx, 5670); assert (node1); zbeacon_t *node2 = zbeacon_new (ctx, 5670); assert (node2); zbeacon_t *node3 = zbeacon_new (ctx, 5670); assert (node3);

assert (*zbeacon_hostname (node1)); assert (*zbeacon_hostname (node2)); assert (*zbeacon_hostname (node3));

zbeacon_set_interval (node1, 250); zbeacon_set_interval (node2, 250); zbeacon_set_interval (node3, 250); zbeacon_noecho (node1); zbeacon_publish (node1, (byte *) "NODE/1", 6); zbeacon_publish (node2, (byte *) "NODE/2", 6); zbeacon_publish (node3, (byte *) "GARBAGE", 7); zbeacon_subscribe (node1, (byte *) "NODE", 4);

// Poll on three API sockets at once zpoller_t *poller = zpoller_new ( zbeacon_socket (node1), zbeacon_socket (node2), zbeacon_socket (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 == zbeacon_socket (node1)); char *ipaddress, *beacon; zstr_recvx (zbeacon_socket (node1), &ipaddress, &beacon, NULL); assert (streq (beacon, "NODE/2")); zstr_free (&ipaddress); zstr_free (&beacon); } } zpoller_destroy (&poller);

// Stop listening zbeacon_unsubscribe (node1);

// Stop all node broadcasts zbeacon_silence (node1); zbeacon_silence (node2); zbeacon_silence (node3);

// Destroy the test nodes zbeacon_destroy (&node1); zbeacon_destroy (&node2); zbeacon_destroy (&node3);

zsock_destroy (&service); zctx_destroy (&ctx);


The czmq manual was written by the authors in the AUTHORS file.


Main web site: \m[blue] \m[]

Report bugs to the email <\m[blue]\m[][1]>


Copyright (c) 1991-2012 iMatix Corporation -- Copyright other contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: 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 LICENSE included with the czmq distribution.


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CZMQ 3&.0&.1 ZBEACON_V2 (3) 06/01/2015

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