[network] Modify iOS port knock to use a valid mDNS packet (openhab#17687)

Signed-off-by: Neil Greatorex <[email protected]>

Author: ngreatorex

bundles/org.openhab.binding.network/src/main/java/org/openhab/binding/network/internal/utils/NetworkUtils.java

@@ -446,7 +446,8 @@ public PingResult javaPing(Duration timeout, InetAddress destinationAddress) {
     public void wakeUpIOS(InetAddress address) throws IOException {
         int port = 5353;
         try (DatagramSocket s = new DatagramSocket()) {
-            byte[] buffer = new byte[0];
+            // Send a valid mDNS packet (12 bytes of zeroes)
+            byte[] buffer = new byte[12];
             s.send(new DatagramPacket(buffer, buffer.length, address, port));
             logger.trace("Sent packet to {}:{} to wake up iOS device", address, port);
         } catch (PortUnreachableException e) {