Use NsdManager to lookup MPD servers on local network

MPDroid/src/main/AndroidManifest.xml

@@ -23,6 +23,8 @@
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.READ_PHONE_STATE" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
+
     <!-- Used to start the service upon boot if the service requires persistence. -->
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <!-- Cover art cache -->

MPDroid/src/main/java/com/cafbit/multicasttest/NetThread.java

@@ -0,0 +1,138 @@
+/*
+ * Copyright 2011 David Simmons
+ * http://cafbit.com/entry/testing_multicast_support_on_android
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.cafbit.multicasttest;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.InetAddress;
+import java.net.MulticastSocket;
+import java.net.NetworkInterface;
+import java.util.Set;
+
+import com.cafbit.netlib.NetUtil;
+import com.cafbit.netlib.dns.DNSMessage;
+
+import android.content.Context;
+import android.net.wifi.WifiManager.MulticastLock;
+import android.util.Log;
+
+/**
+ * This thread runs in the background while the user has our
+ * program in the foreground, and handles sending mDNS queries
+ * and processing incoming mDNS packets.
+ * @author simmons
+ */
+public class NetThread extends Thread {
+
+    private static final String TAG = "NetThread";
+
+    // the standard mDNS multicast address and port number
+    private static final byte[] MDNS_ADDR =
+        new byte[] {(byte) 224,(byte) 0,(byte) 0,(byte) 251};
+    private static final int MDNS_PORT = 5353;
+
+    private static final int BUFFER_SIZE = 4096;
+
+    private NetworkInterface networkInterface;
+    private InetAddress groupAddress;
+    private MulticastSocket multicastSocket = null;
+    private NetUtil netUtil;
+    private String servicename;
+
+    /**
+     * Construct the network thread.
+     * @param activity
+     * @param servicename Name of service to search for
+     */
+    public NetThread(Context activity, String servicename) {
+        super("net");
+        this.servicename = servicename;
+        netUtil = new NetUtil(activity);
+    }
+
+    /**
+     * Open a multicast socket on the mDNS address and port.
+     * @throws IOException
+     */
+    private void openSocket() throws IOException {
+        multicastSocket = new MulticastSocket(MDNS_PORT);
+        multicastSocket.setTimeToLive(2);
+        multicastSocket.setSoTimeout(5000);
+        multicastSocket.setReuseAddress(true);
+        multicastSocket.setNetworkInterface(networkInterface);
+        multicastSocket.joinGroup(groupAddress);
+    }
+
+    /**
+     */
+    @Override
+    public void run() {
+        Log.v(TAG, "starting network thread");
+
+        Set<InetAddress> localAddresses = NetUtil.getLocalAddresses();
+        MulticastLock multicastLock = null;
+
+        try {
+            networkInterface = netUtil.getFirstWifiOrEthernetInterface();
+            if (networkInterface == null) {
+                throw new IOException("Your WiFi is not enabled.");
+            }
+            groupAddress = InetAddress.getByAddress(MDNS_ADDR); 
+
+            multicastLock = netUtil.getWifiManager().createMulticastLock("unmote");
+            multicastLock.acquire();
+            Log.v(TAG, "acquired multicast lock: "+multicastLock);
+
+            openSocket();
+            Log.v(TAG, "opensocket returned");
+
+            query(servicename);
+            Log.v(TAG, "sent query");
+
+            // set up the buffer for incoming packets
+            byte[] responseBuffer = new byte[BUFFER_SIZE];
+            DatagramPacket response = new DatagramPacket(responseBuffer, BUFFER_SIZE);
+            multicastSocket.receive(response);
+            Log.v(TAG, "received response"+response.getSocketAddress());
+            multicastSocket.close();
+        } catch (IOException e1) {
+            Log.v(TAG, "send mdns query failed "+e1.toString());
+            return;
+        }
+
+        if(multicastSocket != null)
+            multicastSocket.close();
+
+        // release the multicast lock
+        if(multicastLock != null)
+            multicastLock.release();
+
+        Log.v(TAG, "stopping network thread");
+    }
+
+    /**
+     * Transmit an mDNS query on the local network.
+     * @param servicename
+     * @throws IOException
+     */
+    private void query(String servicename) throws IOException {
+        byte[] requestData = (new DNSMessage(servicename)).serialize();
+        DatagramPacket request =
+            new DatagramPacket(requestData, requestData.length, InetAddress.getByAddress(MDNS_ADDR), MDNS_PORT);
+        multicastSocket.send(request);
+    }
+}

MPDroid/src/main/java/com/cafbit/multicasttest/Util.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2011 David Simmons
+ * http://cafbit.com/entry/testing_multicast_support_on_android
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.cafbit.multicasttest;
+
+/**
+ * Various mundate utility methods.
+ * @author simmons
+ */
+public class Util {
+
+    public static String hexDump(byte[] bytes) {
+        return hexDump(bytes, 0, bytes.length);
+    }
+
+    public static String hexDump(byte[] bytes, int offset, int length) {
+        StringBuilder sb = new StringBuilder();
+        for (int i=0; i<length; i+=16) {
+            int rowSize = length - i;
+            if (rowSize > 16) { rowSize = 16; }
+            byte[] row = new byte[rowSize];
+            System.arraycopy(bytes, offset+i, row, 0, rowSize);
+            hexDumpRow(sb, row, i);
+        }
+        return sb.toString();
+    }
+
+    private static void hexDumpRow(StringBuilder sb, byte[] bytes, int offset) {
+        sb.append(String.format("%04X: ",offset));
+        for (int i=0; i<16; i++) {
+            if (bytes.length > i) {
+                sb.append(String.format("%02X ",bytes[i]));
+            } else {
+                sb.append("   ");
+            }
+        }
+        for (int i=0; i<16; i++) {
+            if (bytes.length > i) {
+                char c = '.';
+                int v = (int)bytes[i];
+                if ((v > 0x20) && (v < 0x7F)) {
+                    c = (char)v;
+                }
+                sb.append(c);
+            }
+        }
+        sb.append('\n');
+    }
+
+}