added button for mDNS device query

index.html

@@ -27,6 +27,13 @@
     </div>
     <script>require("./startup-render")</script>
 
+    <div>
+      <h3>Device Discovery</h3>
+      <button class="query-devices">Query Devices</button>
+      <div class="found-devices"></div>
+    </div>
+    <script>require("./mdns-render")</script>
+
     <div>
       <button class="crasher">Crash Program</button>
     </div>

index.js

@@ -36,6 +36,7 @@ function createWindow () {
   require('./progress').init(win);
   require('./drag-drop-main').init(win);
   require('./startup-main').init(win);
+  require('./mdns-main').init(win);
 
   // // Open the DevTools.
   // win.webContents.openDevTools();

mdns-main.js

@@ -0,0 +1,90 @@
+'use strict';
+
+var electron = require('electron');
+var dns = require('dns-suite');
+var ipc = electron.ipcMain;
+var win;
+var socket;
+var mdnsPort = 5353;
+var broadcastAddr = '224.0.0.251';
+var queryname = '_cloud._tcp.local';
+
+function sendDeviceQuery() {
+  var id = require('crypto').randomBytes(2).readUInt16LE();
+  var rpacket = {
+    header: {
+      id: id,
+      qr: 0,
+      opcode: 0,
+      aa: 0,
+      tc: 0,
+      rd: 0,
+      ra: 0,
+      res1:  0,
+      res2:  0,
+      res3:  0,
+      rcode: 0,
+    },
+    question: [
+      {
+        name: queryname,
+        typeName: 'PTR',
+        className: 'IN',
+      },
+    ],
+  };
+
+  var buf = dns.DNSPacket.write(rpacket);
+  socket.send(buf, mdnsPort, broadcastAddr, function () {
+    console.log('sent mDNS query', buf.toString('hex'));
+  });
+}
+
+function handleAnswer(message/*, rinfo*/) {
+  // console.log('received %d bytes from %s:%d', message.length, rinfo.address, rinfo.port);
+
+  var packet;
+  try {
+    packet = dns.DNSPacket.parse(message);
+  } catch (error) {
+    // The majority of the packets collected just listening to our local network seem to
+    // throw exceptions, so don't bother logging them.
+    return;
+  }
+
+
+  // We are only interested in responses
+  if (packet.header.qr !== 1) {
+    return;
+  }
+  // And we only want the responses to the question we send (should be sent back in response)
+  if (packet.question.length !== 1 || packet.question[0].name !== queryname) {
+    return;
+  }
+  win.webContents.send('deviceFound', packet);
+}
+
+function init(window) {
+  if (win) {
+    console.error("can't initialize device discovery multiple times");
+    return;
+  }
+  win = window;
+
+  socket = require('dgram').createSocket({ type: 'udp4', reuseAddr: true });
+  socket.on('message', handleAnswer);
+
+  socket.bind(mdnsPort, function () {
+    var addr = this.address();
+    console.log('mDNS device discovery bound on %s:%d', addr.address, addr.port);
+
+    socket.setBroadcast(true);
+    socket.addMembership(broadcastAddr);
+  });
+
+  ipc.on('startDeviceScan', sendDeviceQuery);
+}
+
+module.exports = {
+  init: init,
+};

mdns-render.js

@@ -0,0 +1,14 @@
+'use strict';
+
+var electron = require('electron');
+var ipc = electron.ipcRenderer;
+
+ipc.on('deviceFound', function (e, packet) {
+  console.log(JSON.stringify(packet));
+});
+
+document.body.addEventListener('click', function (ev) {
+  if (ev.target.classList.contains('query-devices')) {
+    ipc.send('startDeviceScan');
+  }
+});

package.json

@@ -19,6 +19,7 @@
     "electron-packager": "^8.6.0"
   },
   "dependencies": {
-    "auto-launch": "^5.0.1"
+    "auto-launch": "^5.0.1",
+    "dns-suite": "git+https://git@git.daplie.com:Daplie/dns-suite#v1"
   }
 }