Added code to ensure that only one instance of the app is running at …

…a time.

src/main/java/com/moglan/eac/application/Config.java

@@ -8,7 +8,8 @@
  */
 public class Config {
 
-	public static final int PORT = 9090;
+	public static final int APP_PORT = 9091;	// used for ensuring that only one instance of the app runs at a time
+	public static final int SERVER_PORT = 9090;
 	public static final int SO_TIMEOUT = 50000;
 
 	private Config() { }

src/main/java/com/moglan/eac/application/Simulation.java

@@ -121,7 +121,7 @@ public void stopSimulation() {
 	public void addClientTask(int sendingFrequency) throws UnknownHostException, IOException {
 		if (clientTasks.size() < Monitor.get().getMaximumNumberOfConnections()) {
 			MeasuringDevice clientTask = new MeasuringDevice("127.0.0.1", 
-					Config.PORT, BASE_PERIOD/sendingFrequency);
+					Config.SERVER_PORT, BASE_PERIOD/sendingFrequency);
 
 			clientTasks.add(clientTask);
 			clientExecutionPool.submit(clientTask);

src/main/java/com/moglan/eac/model/connection/Monitor.java

@@ -25,7 +25,7 @@ public class Monitor extends TCPServer {
 	private volatile int messageCount;	// the total number of received messages throughout the server's up time
 
 	private Monitor() {
-		super(Config.PORT);
+		super(Config.SERVER_PORT);
 
 		messageCount = 0;
 		portAllocation = new HashMap<>();

src/main/java/com/moglan/eac/presentation/MainWindow.java

@@ -3,6 +3,8 @@
 import java.awt.EventQueue;
 import java.awt.event.ActionEvent;
 import java.io.IOException;
+import java.net.InetAddress;
+import java.net.ServerSocket;
 import java.util.Observable;
 import java.util.Observer;
 
@@ -11,6 +13,7 @@
 import javax.swing.UIManager;
 import javax.swing.border.EmptyBorder;
 
+import com.moglan.eac.application.Config;
 import com.moglan.eac.application.Simulation;
 
 import javax.swing.GroupLayout;
@@ -36,7 +39,6 @@
 public class MainWindow extends JFrame implements Observer {
 
 	private static final long serialVersionUID = 1L;
-
 	private JPanel mainPanel;
 	private JProgressBar serverStatusProgressBar;
 	private JButton startSimulationButton;
@@ -61,8 +63,15 @@ public static void main(String[] args) {
 	    }
 
 		EventQueue.invokeLater(new Runnable() {
+			@SuppressWarnings("resource")
 			public void run() {
 				try {
+					/**
+					 * The {@code ServerSocket} instance creation is used for ensuring that only one 
+					 * instance of the app is running at a time.
+					 */
+
+					new ServerSocket(Config.APP_PORT, 0, InetAddress.getByAddress(new byte[] {127,0,0,1}));
 					MainWindow frame = new MainWindow();
 					frame.setVisible(true);
 				} catch (Exception e) {

src/test/java/com/moglan/eac/model/connection/ArchitectureTest.java

@@ -40,7 +40,7 @@ void globalCountTest() {
 			 * Starting dummy server 
 			 */
 
-			server = new DummyServer(Config.PORT);
+			server = new DummyServer(Config.SERVER_PORT);
 
 			server.start();
 
@@ -49,7 +49,7 @@ void globalCountTest() {
 			 */
 
 			for (int i = 0; i < MAX_CLIENTS; i++) {
-				Runnable runnable = new DummyClient(i, LOCALHOST, Config.PORT);
+				Runnable runnable = new DummyClient(i, LOCALHOST, Config.SERVER_PORT);
 				Future<?> future = executionPool.submit(runnable);
 
 				futures.add(future);
@@ -96,7 +96,7 @@ void globalCountTest() {
 	void serverShutdownTest() {
 		TCPServer server = null;
 
-		server = new DummyServer(Config.PORT);
+		server = new DummyServer(Config.SERVER_PORT);
 
 		server.start();