Fix service discovery on android 12

app/src/main/AndroidManifest.xml

@@ -8,6 +8,7 @@
     <uses-permission android:required="true" android:name="android.permission.INTERNET"/>
     <uses-permission android:required="true" android:name="android.permission.RECORD_AUDIO"/>
     <uses-permission android:required="true" android:name="android.permission.ACCESS_WIFI_STATE"/>
+    <uses-permission android:required="true" android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
 
     <application
         android:allowBackup="true"

app/src/main/java/de/rochefort/childmonitor/DiscoverActivity.java

@@ -21,6 +21,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.net.nsd.NsdManager;
 import android.net.nsd.NsdServiceInfo;
+import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.View;
@@ -138,6 +139,31 @@ public class DiscoverActivity extends Activity
     public void startServiceDiscovery(final String serviceType)
     {
         final NsdManager nsdManager = (NsdManager)this.getSystemService(Context.NSD_SERVICE);
+        if (nsdManager == null) {
+            Log.e(TAG, "Could not obtain nsdManager");
+            return;
+        }
+
+        WifiManager wifi = (WifiManager) this.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
+        final Runnable multicastReleaser;
+        if (wifi != null) {
+            final WifiManager.MulticastLock multicastLock = wifi.createMulticastLock("multicastLock");
+            multicastLock.setReferenceCounted(true);
+            multicastLock.acquire();
+            multicastReleaser = new Runnable() {
+                @Override
+                public void run() {
+                    multicastLock.release();
+                }
+            };
+        } else {
+            multicastReleaser = new Runnable() {
+                @Override
+                public void run() {
+                }
+            };
+        }
+
 
         final ListView serviceTable = (ListView) findViewById(R.id.ServiceTable);
 
@@ -218,12 +244,14 @@ public class DiscoverActivity extends Activity
                 // When the network service is no longer available.
                 // Internal bookkeeping code goes here.
                 Log.e(TAG, "Service lost: " + service);
+                multicastReleaser.run();
             }
 
             @Override
             public void onDiscoveryStopped(String serviceType)
             {
                 Log.i(TAG, "Discovery stopped: " + serviceType);
+                multicastReleaser.run();
             }
 
             @Override
@@ -231,6 +259,7 @@ public class DiscoverActivity extends Activity
             {
                 Log.e(TAG, "Discovery failed: Error code: " + errorCode);
                 nsdManager.stopServiceDiscovery(this);
+                multicastReleaser.run();
             }
 
             @Override
@@ -238,6 +267,7 @@ public class DiscoverActivity extends Activity
             {
                 Log.e(TAG, "Discovery failed: Error code: " + errorCode);
                 nsdManager.stopServiceDiscovery(this);
+                multicastReleaser.run();
             }
         };
 

app/src/main/java/de/rochefort/childmonitor/StartActivity.java

@@ -31,6 +31,7 @@ public class StartActivity extends Activity
 {
     static final String TAG = "ChildMonitor";
     private final static int PERMISSIONS_REQUEST_RECORD_AUDIO = 298349824;
+    private final static int PERMISSIONS_REQUEST_MULTICAST = 298349825;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -62,12 +63,21 @@ public class StartActivity extends Activity
             public void onClick(View v)
             {
                 Log.i(TAG, "Starting connection activity");
-                Intent i = new Intent(getApplicationContext(), DiscoverActivity.class);
+                if (isMulticastPermissionGranted()) {
-                startActivity(i);
+                    Intent i = new Intent(getApplicationContext(), DiscoverActivity.class);
+                    startActivity(i);
+                } else {
+                    requestMulticastPermission();
+                }
             }
         });
     }
 
+    private boolean isMulticastPermissionGranted() {
+        return ContextCompat.checkSelfPermission(StartActivity.this, Manifest.permission.CHANGE_WIFI_MULTICAST_STATE)
+                == PackageManager.PERMISSION_GRANTED;
+    }
+
     private boolean isAudioRecordingPermissionGranted() {
         return ContextCompat.checkSelfPermission(StartActivity.this, Manifest.permission.RECORD_AUDIO)
                 == PackageManager.PERMISSION_GRANTED;
@@ -79,11 +89,20 @@ public class StartActivity extends Activity
                 PERMISSIONS_REQUEST_RECORD_AUDIO);
     }
 
+    private void requestMulticastPermission() {
+        ActivityCompat.requestPermissions(StartActivity.this,
+                new String[]{Manifest.permission.CHANGE_WIFI_MULTICAST_STATE},
+                PERMISSIONS_REQUEST_MULTICAST);
+    }
+
     @Override
     public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
         if (requestCode == PERMISSIONS_REQUEST_RECORD_AUDIO && grantResults.length > 0
                 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
             startActivity(new Intent(getApplicationContext(), MonitorActivity.class));
+        } else if (requestCode == PERMISSIONS_REQUEST_MULTICAST) {
+            // its okay if the permission was denied... the user will have to type the address manually
+            startActivity(new Intent(getApplicationContext(), DiscoverActivity.class));
         }
     }
 }