zbeacon_v2(3)

zbeacon_v2(3)

CZMQ Manual - CZMQ/3.0.2

Name

zbeacon_v2 - LAN discovery and presence (deprecated)

Synopsis

//  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);

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. 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.

Example

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");
 return;
}
// 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://127.0.0.1:*");
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 there's 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);

Authors

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

Resources

Main web site:

Report bugs to the email <gro.qmorez.stsil|ved-qmorez#gro.qmorez.stsil|ved-qmorez>

Copyright

Copyright (c) 1991-2012 iMatix Corporation — http://www.imatix.com Copyright other contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for ØMQ: 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.