lib/multicast.js module for finding local peers

lib/multicast.js

@@ -0,0 +1,58 @@
+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 }
+
+  var MULTICAST_ADDR = "233.255.255.255";
+  var PORT = 20000;
+  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);
+    setInterval(sendMessage, 1000);
+    address = socket.address();
+    /*
+    console.log(
+      `UDP socket listening on ${address.address}:${address.port} pid: ${
+        process.pid
+      }`
+    );
+    */
+  });
+
+  function sendMessage() {
+    var msgObj = {
+      gun: {
+        version: Gun.version,
+        port: 8765 // TODO: get actual port instead of default 8765
+      }
+    };
+    var message = Buffer.from(JSON.stringify(msgObj), ENC);
+    socket.send(message, 0, message.length, PORT, MULTICAST_ADDR, function() {
+      // console.info(`Sending message "${message}"`);
+    });
+  }
+
+  socket.on("message", function(message, rinfo) {
+    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]});
+    }
+  });
+});