gun/lib/multicast.js

var Gun = (typeof window !== "undefined")? window.Gun : require('../gun');

Gun.on('create', function(root){
	this.to.next(root);
	var opt = root.opt;
	if(typeof window !== "undefined"){
		return; // do nothing for now - Chrome extensions could use multicast though
	}
	if(false === opt.multicast){ return }
	opt.multicast = opt.multicast || {};

  var MULTICAST_ADDR = "233.255.255.255";
	var MULTICAST_INTERVAL = 1000;
  var PORT = 20000;
	var DEFAULT_GUN_PORT = 8765;
  var ENC = 'utf8';

  var dgram = require("dgram");
  var process = require("process");

  socket = dgram.createSocket({ type: "udp4", reuseAddr: true });

  socket.bind(PORT);

  var address;
  socket.on("listening", function() {
    socket.addMembership(MULTICAST_ADDR);
		if (opt.multicast && opt.multicast.port) { // if port is specified, advertise our node
			console.log(`Advertising this node (port ${opt.multicast.port}) on multicast (${MULTICAST_ADDR})`);
			setInterval(sendMessage, MULTICAST_INTERVAL);
		}
    address = socket.address();
  });

  function sendMessage() {
    var msgObj = {
      gun: {
        version: Gun.version,
        port: opt.multicast.port || DEFAULT_GUN_PORT
      }
    };
    var message = Buffer.from(JSON.stringify(msgObj), ENC);
    socket.send(message, 0, message.length, PORT, MULTICAST_ADDR, function() {
      // console.info(`Sending message "${message}"`);
    });
  }

  socket.on("message", function(message, rinfo) {
    try {
      var msgObj = JSON.parse(message.toString(ENC));
      if (!(msgObj.gun && msgObj.gun.port)) { return }
      var peer = `http://${rinfo.address}:${msgObj.gun.port}`;
      if (!root.opt.peers.hasOwnProperty(peer)) {
        console.log(`peer ${peer} found via multicast`);
        root.$.opt({peers: [peer]});
      }
    } catch (e) {
      // console.error(`Received multicast from ${rinfo.address}:${rinfo.port} but failed to connect:`, e);
    }
  });
});