Register ProtectBabyMonitor service via mDNS

When the MonitorActivity is started it will create a ServerSocket.
The assigned port is then advertised over mDNS for a
"ProtectBabyMonitor" service.

Eventually, when something connects to the ServerSocket audio
data will be streamed out.

src/protect/babymonitor/MonitorActivity.java

@@ -16,22 +16,54 @@
  */
 package protect.babymonitor;
 
+import java.io.IOException;
+import java.net.ServerSocket;
 import android.app.Activity;
+import android.content.Context;
+import android.net.nsd.NsdManager;
+import android.net.nsd.NsdServiceInfo;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.Menu;
 import android.view.MenuItem;
+import android.widget.TextView;
 
 public class MonitorActivity extends Activity
 {
     final String TAG = "BabyMonitor";
 
+    NsdManager _nsdManager;
+
+    NsdManager.RegistrationListener _registrationListener;
+
+    ServerSocket _serverSocket;
     @Override
     protected void onCreate(Bundle savedInstanceState)
     {
         Log.i(TAG, "Baby monitor start");
+
+        _nsdManager = (NsdManager)this.getSystemService(Context.NSD_SERVICE);
+
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_monitor);
+
+        final TextView text = (TextView) findViewById(R.id.textStatus);
+        text.setText("Loading...");
+
+        try
+        {
+            // Initialize a server socket on the next available port.
+            _serverSocket = new ServerSocket(0);
+
+            // Store the chosen port.
+            int localPort = _serverSocket.getLocalPort();
+
+            registerService(localPort);
+        }
+        catch (IOException e)
+        {
+            Log.e(TAG, "Failed to create server socket", e);
+        }
     }
 
     @Override
@@ -39,6 +71,14 @@ public class MonitorActivity extends Activity
     {
         Log.i(TAG, "Baby monitor stop");
 
+        if(_registrationListener != null)
+        {
+            Log.i(TAG, "Unregistering monitoring service");
+
+            _nsdManager.unregisterService(_registrationListener);
+            _registrationListener = null;
+        }
+
         super.onDestroy();
     }
 
@@ -62,4 +102,64 @@ public class MonitorActivity extends Activity
         }
         return super.onOptionsItemSelected(item);
     }
+
+    public void registerService(int port)
+    {
+        NsdServiceInfo serviceInfo  = new NsdServiceInfo();
+        serviceInfo.setServiceName("ProtectBabyMonitor");
+        serviceInfo.setServiceType("_babymonitor._tcp.");
+        serviceInfo.setPort(port);
+
+        _registrationListener = new NsdManager.RegistrationListener()
+        {
+            @Override
+            public void onServiceRegistered(NsdServiceInfo NsdServiceInfo) {
+                // Save the service name.  Android may have changed it in order to
+                // resolve a conflict, so update the name you initially requested
+                // with the name Android actually used.
+                final String serviceName = NsdServiceInfo.getServiceName();
+
+                Log.i(TAG, "Service name: " + serviceName);
+
+                MonitorActivity.this.runOnUiThread(new Runnable() {
+                    @Override
+                    public void run()
+                    {
+                        final TextView statusText = (TextView) findViewById(R.id.textStatus);
+                        statusText.setText("Waiting for connection...");
+
+                        final TextView serviceText = (TextView) findViewById(R.id.textService);
+                        serviceText.setText(serviceName);
+                    }
+                });
+            }
+
+            @Override
+            public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode)
+            {
+                // Registration failed!  Put debugging code here to determine why.
+                Log.e(TAG, "Registration failed: " + errorCode);
+            }
+
+            @Override
+            public void onServiceUnregistered(NsdServiceInfo arg0)
+            {
+                // Service has been unregistered.  This only happens when you call
+                // NsdManager.unregisterService() and pass in this listener.
+
+                Log.i(TAG, "Unregistering service");
+            }
+
+            @Override
+            public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode)
+            {
+                // Unregistration failed.  Put debugging code here to determine why.
+
+                Log.e(TAG, "Unregistration failed: " + errorCode);
+            }
+        };
+
+        _nsdManager.registerService(
+                serviceInfo, NsdManager.PROTOCOL_DNS_SD, _registrationListener);
+    }
 }