Trying to "find" my RaspberryPi on the local WiFi by having it broadcast its IP via a datagram. New to this, but seems like it should work:
Broadcast message:
var Lighthouse = require('../lib/lighthouse.js');
var lh = new Lighthouse();
lh.startBroadcasting();
Listen for a message:
lh.listen();
Both NodeJS 6.7.0
Full code:
var Netmask = require('netmask').Netmask
var dgram = require('dgram');
var os = require('os');
var lighthouse = function Lighthouse() {
this.timer = null;
this.interval = 1;
this.port = 3001;
this.server = dgram.createSocket({type: "udp4", reuseAdr: true});
}
lighthouse.prototype.listen = function() {
var self = this
self.server.on('listening', () => {
var address = self.server.address();
console.log(`server listening ${address.address}:${address.port}`);
});
self.server.on('message', (msg, rinfo) => {
console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);
});
self.server.on('error', (err) => {
console.log(`server error:\n${err.stack}`);
server.close();
});
self.server.on('close', (err) => {
console.log(`server close:\n${err.stack}`);
});
self.server.bind(self.port);
}
lighthouse.prototype.startBroadcasting = function() {
var self = this;
self.address = false;
self.mask = false;
var ifaces = os.networkInterfaces();
Object.keys(ifaces).forEach(function (ifname) {
ifaces[ifname].forEach(function (iface) {
if ('IPv4' !== iface.family || iface.internal !== false) {
return;
}
self.address = iface.address
self.mask = iface.netmask
});
});
if (self.address && self.mask) {
if (self.timer) {
clearInterval(self.timer);
}
self.message = new Buffer("{server: '" + self.address + "'}");
block = new Netmask(self.address + '/' + self.mask);
self.braodcast_address = block.broadcast;
console.log(`Broadcasting to: ${self.braodcast_address}:${self.port}`);
console.log(String(self.message));
}
self.server.bind(function() {
self.server.setBroadcast(true);
self.timer = setInterval(function() {
self.rebroadcast();
}, self.interval * 1000);
});
}
lighthouse.prototype.rebroadcast = function() {
var self = this;
if (self.message) {
self.server.send(self.message, 0, self.message.length, self.port, self.broadcast_address, function() {
console.log(`Sent message: ${self.message}`);
});
}
}
module.exports = lighthouse;
This is the output when the client and server run on the same machine (either machine):
00:20 $ node debug/broadcast.js
Broadcasting to: 10.0.1.255:3001
{server: '10.0.1.7'}
Sent message: {server: '10.0.1.7'}
Sent message: {server: '10.0.1.7'}
Sent message: {server: '10.0.1.7'}
Sent message: {server: '10.0.1.7'}
00:20 $ node debug/listen.js
server listening 0.0.0.0:3001
server got: {server: '10.0.1.7'} from 127.0.0.1:50864
server got: {server: '10.0.1.7'} from 127.0.0.1:50864
server got: {server: '10.0.1.7'} from 127.0.0.1:50864
server got: {server: '10.0.1.7'} from 127.0.0.1:50864
Seems to make contact, however when on separate machines, the listening side stops with just server listening 0.0.0.0:3001
Is broadcast the wrong thing to do here? This answer seems to suggest it should be non-broadcast multicast. Maybe the AirPort router just blocks messages like this. tcpdump like sudo tcpdump -n udp port 3001 seems to show nothing.
