Testen ob Port 1111 verfuegbar, wenn nicht App beenden.

src/main/java/de/uniluebeck/mi/projmi6/Main.java

@@ -26,6 +26,10 @@ import javafx.scene.text.Font;
 import javafx.scene.text.Text;
 import javafx.stage.Stage;
 import javafx.stage.StageStyle;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.ServerSocket;
 
 
 public class Main extends Application {
@@ -98,9 +102,35 @@ public class Main extends Application {
      * @param args Commandline parameters
      */
     public static void main(String[] args) {
+        if (isRunning()) {
+            LoggerFactory.getLogger(Main.class).error("App already running or Port 1111 in use.");
+            System.exit(2);
+        }
+
         launch(args);
     }
 
+    /**
+     * @return true wenn der Port 1111 bereits belegt ist, false sonst.
+     */
+    private static boolean isRunning() {
+        ServerSocket socket = null;
+        try {
+            socket = new ServerSocket(1111);
+            socket.setReuseAddress(true);
+            return false;
+        } catch (IOException ignored) {
+        } finally {
+            if (socket != null) {
+                try {
+                    socket.close();
+                } catch (IOException ignored) {
+                }
+            }
+        }
+        return true;
+    }
+
     @Override
     public void stop() throws Exception {
         if (server != null) {