Added error handling and comments to ServiceDiscoveryThread. Assorted logging.

src/ve/ucv/ciens/ccg/nxtar/Main.java

@@ -102,11 +102,11 @@ public class Main implements ApplicationListener, NetworkConnectionListener {
 	}
 
 	@Override
-	public synchronized void interfaceConnected(String iface) {
+	public synchronized void networkStreamConnected(String streamName) {
-		if(iface.compareTo(VideoStreamingThread.THREAD_NAME) == 0 || iface.compareTo(RobotControlThread.THREAD_NAME) == 0)
+		if(streamName.compareTo(VideoStreamingThread.THREAD_NAME) == 0 || streamName.compareTo(RobotControlThread.THREAD_NAME) == 0)
 			connections += 1;
 		if(connections >= 2){
-			Gdx.app.debug(TAG, CLASS_NAME + ".interfaceConnected() :: Stopping service broadcast.");
+			Gdx.app.debug(TAG, CLASS_NAME + ".networkStreamConnected() :: Stopping service broadcast.");
 			udpThread.finish();
 			mcastEnabler.disableMulticast();
 		}

src/ve/ucv/ciens/ccg/nxtar/interfaces/NetworkConnectionListener.java

@@ -1,5 +1,5 @@
 package ve.ucv.ciens.ccg.nxtar.interfaces;
 
 public interface NetworkConnectionListener {
-	public void interfaceConnected(String iface);
+	public void networkStreamConnected(String streamName);
 }

src/ve/ucv/ciens/ccg/nxtar/network/RobotControlThread.java

@@ -42,7 +42,7 @@ public class RobotControlThread extends Thread {
 		try{
 			client = server.accept();
 			if(netListener != null)
-				netListener.interfaceConnected(THREAD_NAME);
+				netListener.networkStreamConnected(THREAD_NAME);
 			toaster.showShortToast("Client connected to RobotControlThread");
 			client.close();
 		}catch(IOException io){

src/ve/ucv/ciens/ccg/nxtar/network/ServiceDiscoveryThread.java

@@ -10,10 +10,36 @@ import ve.ucv.ciens.ccg.nxtar.utils.ProjectConstants;
 
 import com.badlogic.gdx.Gdx;
 
+/**
+ * Ad hoc service discovery server thread.
+ * 
+ * <p> This thread performs an ad hoc service discovery protocol. A multicast datagram packet is sent every
+ * 250 miliseconds carrying the string "NxtAR server is here!" on the multicast address defined 
+ * in {@link ve.ucv.ciens.ccg.nxtar.utils.ProjectConstants#MULTICAST_ADDRESS}. The port defined in
+ * {@link ve.ucv.ciens.ccg.nxtar.utils.ProjectConstants#SERVER_UDP_PORT} is used for the transmissions. The server stops
+ * when another thread calls the {@link #finish()} method or the server fails to transmit {@link #MAX_RETRIES} packets in
+ * a row, whichever happens first.</p>
+ * 
+ * @author miky
+ * @since 27/11/2013
+ */
 public class ServiceDiscoveryThread extends Thread {
+	/**
+	 * The name used to identify this thread.
+	 */
 	public static final String THREAD_NAME = "ServiceDiscoveryThread";
+	/**
+	 * Tag used for logging.
+	 */
 	private static final String TAG = "NXTAR_CORE_UDPTHREAD";
+	/**
+	 * Class name used for logging.
+	 */
 	private static final String CLASS_NAME = ServiceDiscoveryThread.class.getSimpleName();
+	/**
+	 * Maximum number of transmission attempts before ending the thread abruptly.
+	 */
+	private static final int MAX_RETRIES = 5;
 
 	private Object semaphore;
 	private boolean done;
@@ -21,48 +47,82 @@ public class ServiceDiscoveryThread extends Thread {
 	private InetAddress group;
 
 	public ServiceDiscoveryThread(){
+		// Setup this thread name.
 		super(THREAD_NAME);
 
 		done = false;
 		semaphore = new Object();
 
+		// Try to get the InetAddress defined by the IP address defined in ProjectConstants.MULTICAST_ADDRESS.
 		try{
 			group = InetAddress.getByName(ProjectConstants.MULTICAST_ADDRESS);
-		}catch(UnknownHostException uh){ }
+		}catch(UnknownHostException uh){
+			group = null;
+		}
 
+		// Create a UDP socket at the port defined in ProjectConstants.SERVER_UDP_PORT.
 		Gdx.app.debug(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Creating multicast server.");
 		try{
 			udpServer = new DatagramSocket(ProjectConstants.SERVER_UDP_PORT);
 		}catch(IOException io){
-			Gdx.app.error(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Error creating UDP socket: " + io.getMessage(), io);
+			Gdx.app.error(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Error creating UDP socket: " + io.getMessage());
+			udpServer = null;
 		}
 		Gdx.app.debug(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Multicast server created.");
 	}
 
 	@Override
 	public void run(){
+		int retries = 0;
 		byte[] buffer = (new String("NxtAR server here!")).getBytes();
-		try{
+
-			while(true){
+		// If failed to get any of the required network elements then end the thread right away.
-				synchronized(semaphore){
+		if(group == null || udpServer == null){
-					if(done){
+			Gdx.app.error(TAG, CLASS_NAME + ".run() :: No multicast address defined, ending thread.");
-						udpServer.close();
+			return;
-						break;
+		}
-					}
+		if(group == null){
+			Gdx.app.error(TAG, CLASS_NAME + ".run() :: No server available, ending thread.");
+			return;
+		}
+
+		while(true){
+			// Verify if the thread should end. If that is the case, close the server.
+			synchronized(semaphore){
+				if(done){
+					udpServer.close();
+					break;
 				}
-				//Gdx.app.debug(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Resending packet");
+			}
+			try{
+				// End the thread if already at the last retry attempt after too many failed transmissions.
+				if(retries >= MAX_RETRIES){
+					Gdx.app.error(TAG, CLASS_NAME + ".run() :: Too many failed transmissions, ending thread.");
+					udpServer.close();
+					break;
+				}
+				// Send the packet and reset the retry counter.
 				DatagramPacket packet = new DatagramPacket(buffer, buffer.length, group, ProjectConstants.SERVER_UDP_PORT);
 				udpServer.send(packet);
-				//Gdx.app.debug(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Packet sent");
+				retries = 0;
 				try{ sleep(250L); }catch(InterruptedException ie){ }
+			}catch(IOException io){
+				Gdx.app.error(TAG, CLASS_NAME + ".run() :: Error sending packet: " + io.getMessage());
+				retries += 1;
 			}
-		}catch(IOException io){
-			Gdx.app.debug(TAG, CLASS_NAME + ".ServiceDiscoveryThread() :: Error sending packet: " + io.getMessage(), io);
 		}
+		if(retries < MAX_RETRIES)
+			Gdx.app.debug(TAG, CLASS_NAME + ".run() :: Service discovery successfully terminated.");
+		else
+			Gdx.app.debug(TAG, CLASS_NAME + ".run() :: Service discovery terminated after too many failed transmissions.");
 	}
 
+	/**
+	 * Marks this thread as ready to end.
+	 */
 	public void finish(){
 		synchronized(semaphore){
+			Gdx.app.debug(TAG, CLASS_NAME + ".finish() :: Finishing service discovery thread.");
 			done = true;
 		}
 	}

src/ve/ucv/ciens/ccg/nxtar/network/VideoStreamingThread.java

@@ -42,7 +42,7 @@ public class VideoStreamingThread extends Thread {
 		try{
 			client = server.accept();
 			if(netListener != null)
-				netListener.interfaceConnected(THREAD_NAME);
+				netListener.networkStreamConnected(THREAD_NAME);
 			toaster.showShortToast("Client connected to VideoStreamingThread");
 			client.close();
 		}catch(IOException io){