Message types and server (#44)

* message type and handling

* deleted web-content and fixed bug

* edited main page

Backend/pom.xml

@@ -135,5 +135,11 @@
       <groupId>io.github.cdimascio</groupId>
       <version>3.0.0</version>
     </dependency>
+    <!-- Jackson for JSON serialization/deserialization -->
+    <dependency>
+      <groupId>org.json</groupId>
+      <artifactId>json</artifactId>
+      <version>20240303</version>
+    </dependency>
   </dependencies>
 </project>

Backend/schafkopf-client/pom.xml

@@ -41,7 +41,7 @@
           </descriptorRefs>
           <archive>
             <manifest>
-              <mainClass>org.schafkopf.BackendServer</mainClass>
+              <mainClass>org.schafkopf.SchafkopfClient</mainClass>
             </manifest>
           </archive>
         </configuration>

Backend/schafkopf-client/src/main/java/org/schafkopf/BackendServer.java

@@ -1,63 +1,44 @@
 package org.schafkopf;
 
-import com.sun.net.httpserver.HttpExchange;
-import com.sun.net.httpserver.HttpHandler;
-import com.sun.net.httpserver.HttpServer;
 import jakarta.servlet.DispatcherType;
 import java.awt.Desktop;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.net.InetSocketAddress;
 import java.net.URI;
-import java.net.URISyntaxException;
 import java.net.URL;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.List;
-import java.util.concurrent.CountDownLatch;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
+import org.eclipse.jetty.servlet.DefaultServlet;
 import org.eclipse.jetty.servlet.FilterHolder;
 import org.eclipse.jetty.servlet.ServletContextHandler;
+import org.eclipse.jetty.servlet.ServletHolder;
 import org.eclipse.jetty.servlets.CrossOriginFilter;
 import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
-import org.schafkopf.cardreader.UsbCardReader;
-import org.schafkopf.player.BotPlayer;
-import org.schafkopf.player.LocalPlayer;
-import org.schafkopf.player.Player;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
 
-/** Main Class that represents the Backend Server. */
+/**
+ * Main Class that represents the Backend Server.
+ */
 public class BackendServer implements MessageSender {
-  private final Server server;
-  private final ServerConnector connector;
-  private CountDownLatch nfcLatch = new CountDownLatch(1);
-  private Boolean readingMode = false;
-  private String uidString = "";
 
-  /** Important variables. */
-  public final Schafkopf schafkopfGame;
+  private final Server server;
 
   private final List<FrontendEndpoint> frontendEndpoints = new ArrayList<>();
 
-  private DedicatedServerConnection dedicatedServerConnection;
-
-  /** Creates an Instance of the Backend Server. */
-  public BackendServer() throws URISyntaxException, IOException {
+  /**
+   * Creates an Instance of the Backend Server.
+   */
+  public BackendServer(String hostName, int port, boolean openFrontend,
+      MessageListener messageListener) throws Exception {
     server = new Server();
-    InetSocketAddress address = new InetSocketAddress("localhost", 8080);
-    connector = new ServerConnector(server);
-    connector.setHost(address.getHostName());
-    connector.setPort(address.getPort());
+
+    ServerConnector connector = new ServerConnector(server);
+    connector.setHost(hostName);
+    connector.setPort(port);
     server.addConnector(connector);
 
-    schafkopfGame = new Schafkopf(new Player[]{new BotPlayer(), new LocalPlayer(this),
-        new LocalPlayer(this),
-        new LocalPlayer(this)}, this);
-
-    new UsbCardReader(this);
-
     // Setup the basic application "context" for this application at "/"
     // This is also known as the handler tree (in jetty speak)
     ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
@@ -71,11 +52,9 @@ public class BackendServer implements MessageSender {
     if (webContentUrl == null) {
       throw new RuntimeException("Unable to find 'web-content' directory");
     }
-
     String webContentPath = webContentUrl.toExternalForm();
     context.setResourceBase(webContentPath);
-
-    System.out.println("Web Content Path: " + webContentPath);
+    context.addServlet(new ServletHolder("frontend", DefaultServlet.class), "/");
 
     // Configure specific websocket behavior
     JettyWebSocketServletContainerInitializer.configure(
@@ -85,83 +64,25 @@ public class BackendServer implements MessageSender {
           wsContainer.setMaxTextMessageSize(65535);
           wsContainer.setIdleTimeout(Duration.ofDays(300000));
           // Add websockets
-          wsContainer.addMapping("/schafkopf-events/*", new FrontendEndpointCreator(this));
+          wsContainer.addMapping("/schafkopf-events/*",
+              new FrontendEndpointCreator(this, messageListener));
         });
 
-    // Integrate simple HTTP server
-    startHttpServer();
-    URI uri = new URI("http://localhost:8081"); // Replace with your target URL
-    Desktop.getDesktop().browse(uri);
-
-    startDedicatedServerConnectionThread();
-  }
-
-  private void startDedicatedServerConnectionThread() {
-    dedicatedServerConnection = new DedicatedServerConnection(this);
-    dedicatedServerConnection.connect();
-  }
-
-  private void startHttpServer() {
-    try {
-      HttpServer httpServer = HttpServer.create(new InetSocketAddress(8081), 0);
-      httpServer.createContext("/", new MyHandler());
-      httpServer.setExecutor(null);
-      httpServer.start();
-      System.out.println("HTTP Server started on port 8081");
-    } catch (IOException e) {
-      e.printStackTrace();
+    if (openFrontend) {
+      URI uri = new URI("http://" + hostName + ":" + port); // Replace with your target URL
+      Desktop.getDesktop().browse(uri);
     }
-  }
-
-  static class MyHandler implements HttpHandler {
-    @Override
-    public void handle(HttpExchange t) throws IOException {
-      String path = t.getRequestURI().getPath();
-      if ("/".equals(path)) {
-        path = "/index.html"; // default to index.html
-      }
 
+    // Start the server in a separate thread
+    Thread serverThread = new Thread(() -> {
       try {
-        InputStream fileStream =
-            getClass().getClassLoader().getResourceAsStream("web-content" + path);
-        if (fileStream != null) {
-          byte[] data = fileStream.readAllBytes();
-          // Set the appropriate MIME type for JavaScript files
-          String mimeType = getMimeType(path);
-          t.getResponseHeaders().set("Content-Type", mimeType);
-          t.sendResponseHeaders(200, data.length);
-
-          try (OutputStream os = t.getResponseBody()) {
-            os.write(data);
-          }
-        } else {
-          // File not found
-          t.sendResponseHeaders(404, -1);
-        }
-      } catch (IOException e) {
+        server.start();
+        server.join(); // Wait for server to finish execution
+      } catch (Exception e) {
         e.printStackTrace();
-        t.sendResponseHeaders(500, -1);
       }
-    }
-
-    private String getMimeType(String path) {
-      if (path.endsWith(".js")) {
-        return "application/javascript";
-      } else if (path.endsWith(".html")) {
-        return "text/html";
-      } else if (path.endsWith(".css")) {
-        return "text/css";
-      }
-      // Add more MIME types as needed
-      return "application/octet-stream";
-    }
-  }
-
-  /** The main entrypoint of the Application. */
-  public static void main(String[] args) throws Exception {
-    BackendServer server = new BackendServer();
-    server.start();
-    server.join();
+    });
+    serverThread.start();
   }
 
   private void configureCors(ServletContextHandler context) {
@@ -205,39 +126,14 @@ public class BackendServer implements MessageSender {
     }
   }
 
-  /** method to call to wait for NFC input. */
-  public String waitForCardScan() throws InterruptedException {
-    this.readingMode = true;
-    nfcLatch.await();
-    Thread.sleep(20);
-    this.readingMode = false;
-    nfcLatch = new CountDownLatch(1);
-    return this.uidString;
-  }
-
-  /**
-   * checks uid of scanned card and do nothing if Server is not in reading mode.
-   *
-   * @param uidString uid to check.
-   */
-  public void nfcGelesen(String uidString) {
-    if (this.uidString.equals(uidString)) {
-      return;
-    }
-    if (!this.readingMode) {
-      return;
-    }
-
-    this.uidString = uidString;
-    nfcLatch.countDown();
-  }
-
-  public void startDedicatedServerGame() {
-    dedicatedServerConnection.start();
-  }
-
   @Override
-  public void sendMessage(String message) {
+  public void sendMessage(SchafkopfBaseMessage message) {
+    sendMessageToAllFrontendEndpoints(
+        message.getBaseMessage().toString());
+  }
+
+
+  public void sendMessageTest(String message) {
     sendMessageToAllFrontendEndpoints(message);
   }
 }

Backend/schafkopf-client/src/main/java/org/schafkopf/DedicatedServerConnection.java

@@ -1,6 +1,8 @@
 package org.schafkopf;
 
+import com.google.gson.JsonObject;
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.concurrent.CountDownLatch;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
@@ -10,30 +12,58 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
 import org.eclipse.jetty.websocket.client.ClientUpgradeRequest;
 import org.eclipse.jetty.websocket.client.WebSocketClient;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageOrigin;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageType;
 
-/** Main Class that represents the Backend Server. */
+/**
+ * Main Class that represents the Backend Server.
+ */
 @WebSocket
-public class DedicatedServerConnection {
+public class DedicatedServerConnection implements MessageSender {
 
-  private final MessageSender messageSender;
+  private final MessageListener messageListener;
   private final CountDownLatch closeLatch;
+  private final CountDownLatch connectionLatch;
   private static Session session;
 
-  public DedicatedServerConnection(MessageSender messageSender) {
-    this.messageSender = messageSender;
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public DedicatedServerConnection(String address, MessageListener messageListener) {
+    URI uri = null;
+    try {
+      uri = new URI(address);
+    } catch (URISyntaxException e) {
+      throw new RuntimeException(e);
+    }
+
+    this.messageListener = messageListener;
     this.closeLatch = new CountDownLatch(1);
+    this.connectionLatch = new CountDownLatch(1);
+
+    String host = uri.getHost();
+    int port = uri.getPort();
+    connect("ws://" + host + ":" + port);
+    try {
+      connectionLatch.await(); // Wait until the connection is established
+    } catch (InterruptedException e) {
+      System.err.println("Error waiting for connection: " + e.getMessage());
+    }
   }
 
+  /**
+   * Class that represents one Frontend Connection.
+   */
   @OnWebSocketConnect
   public void onConnect(Session session) {
     this.session = session;
-    System.out.println("Connected to server.");
+    connectionLatch.countDown();
   }
 
   @OnWebSocketMessage
   public void onMessage(String message) {
-    messageSender.sendMessage(message);
-    System.out.println("Received message from server: " + message);
+    messageListener.receiveMessage(message);
   }
 
   @OnWebSocketClose
@@ -47,10 +77,14 @@ public class DedicatedServerConnection {
     System.err.println("Error occurred: " + cause.getMessage());
   }
 
-  /** Main Class that represents the Backend Server. */
-  public static void sendMessage(String message) {
+  /**
+   * Main Class that represents the Backend Server.
+   */
+  @Override
+  public void sendMessage(SchafkopfBaseMessage message) {
     try {
-      session.getRemote().sendString(message);
+      session.getRemote().sendString(
+          new SchafkopfMessage(SchafkopfMessageOrigin.BACKEND, message).getMessageAsString());
       System.out.println("Sent message to server: " + message);
     } catch (Exception e) {
       System.err.println("Error sending message: " + e.getMessage());
@@ -61,15 +95,15 @@ public class DedicatedServerConnection {
     closeLatch.await();
   }
 
-  /** Main Class that represents the Backend Server. */
-  public void connect() {
+  /**
+   * Main Class that represents the Backend Server.
+   */
+  public void connect(String serverUri) {
     Thread connectionThread = new Thread(() -> {
       try {
-        String serverUri = "ws://localhost:8085/";
         WebSocketClient client = new WebSocketClient();
         try {
           client.start();
-          //DedicatedServerConnection socketClient = new DedicatedServerConnection();
           HeartbeatSender heartbeatSender = new HeartbeatSender(this);
           heartbeatSender.start(); // Start sending heartbeat messages
           URI uri = new URI(serverUri);
@@ -95,7 +129,23 @@ public class DedicatedServerConnection {
     start();
   }
 
-  public static void start() {
-    sendMessage("START_GAME");
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public void start() {
+    JsonObject messageObject = new JsonObject();
+
+    messageObject.addProperty("message_type", "START_GAME");
+    sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.START_GAME));
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public void join() {
+    JsonObject messageObject = new JsonObject();
+
+    messageObject.addProperty("message_type", "JOIN_GAME");
+    sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.JOIN_GAME));
   }
 }

Backend/schafkopf-client/src/main/java/org/schafkopf/FrontendEndpoint.java

@@ -5,16 +5,27 @@ import java.util.concurrent.CountDownLatch;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.WebSocketAdapter;
 
-/** Class that represents one Frontend Connection. */
+/**
+ * Class that represents one Frontend Connection.
+ */
 public class FrontendEndpoint extends WebSocketAdapter {
+
   private final CountDownLatch closureLatch = new CountDownLatch(1);
   private BackendServer backendServer;
+  private final MessageListener messageListener;
 
-  public FrontendEndpoint(BackendServer backendServer) {
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public FrontendEndpoint(BackendServer backendServer, MessageListener messageListener) {
+    this.messageListener = messageListener;
     this.backendServer = backendServer;
     System.out.println("new FrontendEndpoint");
   }
 
+  /**
+   * Class that represents one Frontend Connection.
+   */
   @Override
   public void onWebSocketConnect(Session session) {
     super.onWebSocketConnect(session);
@@ -27,20 +38,9 @@ public class FrontendEndpoint extends WebSocketAdapter {
   @Override
   public void onWebSocketText(String message) {
     super.onWebSocketText(message);
-    System.out.println("Received TEXT message:" + message);
-
-    if (message.contains("startsimulation")) {
-      backendServer.schafkopfGame.startGame();
+    if (messageListener != null) {
+      messageListener.receiveMessage(message); // Notify the listener
     }
-
-    if (message.contains("stopsimulation")) {
-      backendServer.schafkopfGame.stopGame();
-    }
-
-    if (message.contains("startdedicated")) {
-      backendServer.startDedicatedServerGame();
-    }
-
   }
 
   @Override
@@ -59,7 +59,9 @@ public class FrontendEndpoint extends WebSocketAdapter {
     cause.printStackTrace(System.err);
   }
 
-  /** send a Message to the connected FrontEnd. */
+  /**
+   * send a Message to the connected FrontEnd.
+   */
   public void sendMessage(String message) {
     try {
       getRemote().sendString(message);

Backend/schafkopf-client/src/main/java/org/schafkopf/FrontendEndpointCreator.java

@@ -9,8 +9,10 @@ import org.eclipse.jetty.websocket.server.JettyWebSocketCreator;
  */
 public class FrontendEndpointCreator implements JettyWebSocketCreator {
   private BackendServer backendServer;
+  private final MessageListener messageListener;
 
-  public FrontendEndpointCreator(BackendServer backendServer) {
+  public FrontendEndpointCreator(BackendServer backendServer, MessageListener messageListener) {
+    this.messageListener = messageListener;
     this.backendServer = backendServer;
   }
 
@@ -18,6 +20,6 @@ public class FrontendEndpointCreator implements JettyWebSocketCreator {
   public Object createWebSocket(
       JettyServerUpgradeRequest jettyServerUpgradeRequest,
       JettyServerUpgradeResponse jettyServerUpgradeResponse) {
-    return new FrontendEndpoint(this.backendServer);
+    return new FrontendEndpoint(this.backendServer, messageListener);
   }
 }

Backend/schafkopf-client/src/main/java/org/schafkopf/HeartbeatSender.java

@@ -2,9 +2,13 @@ package org.schafkopf;
 
 import java.util.Timer;
 import java.util.TimerTask;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
 
-/** Creates an Instance of the Backend Server. */
+/**
+ * Creates an Instance of the Backend Server.
+ */
 public class HeartbeatSender {
+
   private static final int HEARTBEAT_INTERVAL = 15000; // 1 minute
 
   private final DedicatedServerConnection client;
@@ -13,13 +17,16 @@ public class HeartbeatSender {
     this.client = client;
   }
 
-  /** Creates an Instance of the Backend Server. */
+  /**
+   * Creates an Instance of the Backend Server.
+   */
   public void start() {
     Timer timer = new Timer();
     timer.scheduleAtFixedRate(new TimerTask() {
       @Override
       public void run() {
-        client.sendMessage("HEARTBEAT SYN"); // Send a heartbeat message
+        client.sendMessage(
+            new SchafkopfBaseMessage(SchafkopfMessage.SchafkopfMessageType.HEARTBEAT_SYN));
       }
     }, HEARTBEAT_INTERVAL, HEARTBEAT_INTERVAL);
   }

Backend/schafkopf-client/src/main/java/org/schafkopf/SchafkopfClient.java

@@ -0,0 +1,81 @@
+package org.schafkopf;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageOrigin;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageType;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public class SchafkopfClient implements MessageListener {
+
+  private BackendServer backendServer;
+  private DedicatedServerConnection dedicatedServerConnection;
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public SchafkopfClient() throws Exception {
+
+    this.backendServer = new BackendServer("localhost", 8080, true, this);
+
+    System.out.println("Client started.");
+  }
+
+  public static void main(String[] args) throws Exception {
+    new SchafkopfClient();
+  }
+
+  @Override
+  public void receiveMessage(String jsonMessage) {
+    Gson gson = new Gson();
+    JsonObject jsonObject = gson.fromJson(jsonMessage, JsonObject.class);
+    // Check if the origin is "frontend"
+    String origin = jsonObject.get("origin").getAsString();
+    if (SchafkopfMessageOrigin.FRONTEND.toString().equals(origin)) {
+      JsonObject message = jsonObject.getAsJsonObject("message");
+      JsonObject content = message.getAsJsonObject("content");
+      String messageType = message.get("message_type").getAsString();
+      if (SchafkopfMessageType.REQUEST_SERVER_CONNECTION.toString().equals(messageType)) {
+        dedicatedServerConnection = new DedicatedServerConnection(
+            content.get("serverAddress").getAsString(),
+            this);
+      } else if ("JOIN_GAME".equals(messageType)) {
+        dedicatedServerConnection.join();
+      } else if ("START_DEDICATED_GAME".equals(messageType)) {
+        dedicatedServerConnection.start();
+      } else if (SchafkopfMessageType.PLAYER_CARD.toString().equals(messageType)) {
+        dedicatedServerConnection.sendMessage(
+            new SchafkopfBaseMessage(SchafkopfMessageType.PLAYER_CARD, content));
+      }
+
+      System.out.println("Received message from frontend server: " + jsonMessage);
+
+    } else if (SchafkopfMessageOrigin.DEDICATED_SERVER.toString().equals(origin)) {
+
+      JsonObject message = jsonObject.getAsJsonObject("message");
+      JsonObject content = message.getAsJsonObject("content");
+      String messageType = message.get("message_type").getAsString();
+      if (SchafkopfMessageType.GET_CARD_ONLINE_PLAYER.toString().equals(messageType)) {
+        System.out.println("Received get_card_online_player message from dedicated server.");
+      } else if (SchafkopfMessageType.GAME_STATE.toString().equals(messageType)) {
+        backendServer.sendMessage(
+            new SchafkopfBaseMessage(SchafkopfMessage.SchafkopfMessageType.GAME_STATE, content));
+      } else if (SchafkopfMessageType.ONLINE_PLAYER_HAND.toString().equals(messageType)) {
+        backendServer.sendMessage(
+            new SchafkopfBaseMessage(SchafkopfMessage.SchafkopfMessageType.ONLINE_PLAYER_HAND,
+                content));
+      } else if (SchafkopfMessageType.SERVER_CONNECTION_SUCCESSFUL.toString().equals(messageType)) {
+        System.out.println("Received server_connection_successful message from dedicated server.");
+        backendServer.sendMessage(new SchafkopfBaseMessage(
+            SchafkopfMessage.SchafkopfMessageType.SERVER_CONNECTION_SUCCESSFUL));
+      } else if (SchafkopfMessageType.HEARTBEAT_ACK.toString().equals(messageType)) {
+        return;
+      }
+      System.out.println("Received message from dedicated server: " + jsonMessage);
+    }
+  }
+}
+

Backend/schafkopf-client/src/main/java/org/schafkopf/cardreader/CardReader.java

@@ -1,13 +1,42 @@
 package org.schafkopf.cardreader;
 
-import org.schafkopf.BackendServer;
+import java.util.concurrent.CountDownLatch;
 
 /** Class that represents one Card Reader. */
 public abstract class CardReader {
 
-  protected static BackendServer server;
+  private CountDownLatch nfcLatch = new CountDownLatch(1);
+  private Boolean readingMode = false;
+  private String uidString = "";
 
-  public CardReader(BackendServer server) {
-    this.server = server;
+  public CardReader() {
+
+  }
+
+  /** method to call to wait for NFC input. */
+  public String waitForCardScan() throws InterruptedException {
+    this.readingMode = true;
+    nfcLatch.await();
+    Thread.sleep(20);
+    this.readingMode = false;
+    nfcLatch = new CountDownLatch(1);
+    return this.uidString;
+  }
+
+  /**
+   * checks uid of scanned card and do nothing if Server is not in reading mode.
+   *
+   * @param uidString uid to check.
+   */
+  public void nfcGelesen(String uidString) {
+    if (this.uidString.equals(uidString)) {
+      return;
+    }
+    if (!this.readingMode) {
+      return;
+    }
+
+    this.uidString = uidString;
+    nfcLatch.countDown();
   }
 }

Backend/schafkopf-client/src/main/java/org/schafkopf/cardreader/UsbCardReader.java

@@ -16,10 +16,8 @@ public class UsbCardReader extends CardReader {
   /**
    * Creates an Instance of the KartenLeser.
    *
-   * @param server Backend Server to call methods on.
    */
-  public UsbCardReader(BackendServer server) {
-    super(server);
+  public UsbCardReader() {
     new Thread(this::run).start();
   }
 
@@ -80,7 +78,7 @@ public class UsbCardReader extends CardReader {
             String data = new String(buffer, 0, bytesRead, "UTF-8").trim();
 
             // Process the received data
-            server.nfcGelesen(data);
+            this.nfcGelesen(data);
           }
 
           // Optional: Add a delay to avoid consuming too much CPU

Backend/schafkopf-client/src/main/java/org/schafkopf/player/LocalPlayer.java

@@ -1,6 +1,7 @@
 package org.schafkopf.player;
 
 import org.schafkopf.BackendServer;
+import org.schafkopf.cardreader.CardReader;
 import org.schafkopf.karte.Karte;
 import org.schafkopf.karte.KartenListe;
 import org.schafkopf.karte.KartenUtil;
@@ -11,10 +12,10 @@ import org.schafkopf.spielcontroller.SpielController;
  */
 public class LocalPlayer extends Player {
 
-  private final BackendServer server;
+  private final CardReader cardReader;
 
-  public LocalPlayer(BackendServer server) {
-    this.server = server;
+  public LocalPlayer(CardReader cardReader) {
+    this.cardReader = cardReader;
   }
 
   @Override
@@ -27,7 +28,7 @@ public class LocalPlayer extends Player {
     String uid = null;
     System.out.println("Starte Warten auf Karte");
     try {
-      uid = server.waitForCardScan();
+      uid = cardReader.waitForCardScan();
     } catch (InterruptedException e) {
       throw new RuntimeException(e);
     }

Backend/schafkopf-client/src/main/resources/web-content/index.html

@@ -1,13 +0,0 @@
-<!doctype html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8"/>
-    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
-    <title>Vite + Vue + TS</title>
-  <script type="module" crossorigin src="/assets/index-DZ_vcdmw.js"></script>
-  <link rel="stylesheet" crossorigin href="/assets/index-8PJRhba5.css">
-</head>
-<body class="bg-zinc-800">
-<div id="app"></div>
-
-</body>

Backend/schafkopf-server/src/main/java/org/schafkopf/ClientConnection.java

@@ -1,75 +0,0 @@
-package org.schafkopf;
-
-import java.io.IOException;
-import java.util.concurrent.CountDownLatch;
-import org.eclipse.jetty.websocket.api.Session;
-import org.eclipse.jetty.websocket.api.WebSocketAdapter;
-import org.schafkopf.player.BotPlayer;
-import org.schafkopf.player.Player;
-
-/** Class that represents one Frontend Connection. */
-public class ClientConnection extends WebSocketAdapter implements MessageSender {
-  private final CountDownLatch closureLatch = new CountDownLatch(1);
-  private DedicatedServer dedicatedServer;
-
-  private Session session;
-
-  public ClientConnection(DedicatedServer dedicatedServer) {
-    this.dedicatedServer = dedicatedServer;
-    System.out.println("new ClientConnection created.");
-  }
-
-  @Override
-  public void onWebSocketConnect(Session session) {
-    this.session = session;
-    super.onWebSocketConnect(session);
-    String clientIp = session.getRemoteAddress().toString();
-    System.out.println("Endpoint connected from ip: " + clientIp);
-
-    dedicatedServer.addFrontendEndpoint(this);
-  }
-
-  @Override
-  public void onWebSocketText(String message) {
-    super.onWebSocketText(message);
-    if (message.equals("HEARTBEAT SYN")) {
-      System.out.println("Received HEARTBEAT message from " + session.getRemoteAddress() + ".");
-      sendMessage("HEARTBEAT ACK");
-      return;
-    }
-    if (message.equals("START_GAME")) {
-      System.out.println("Received START_GAME message from " + session.getRemoteAddress() + ".");
-      dedicatedServer.addGameSession(new GameSession(new Schafkopf(new Player[] {
-        new BotPlayer(), new BotPlayer(), new BotPlayer(), new BotPlayer()
-      }, this)));
-      return;
-    }
-    System.out.println("Received TEXT message:" + message);
-  }
-
-  @Override
-  public void onWebSocketClose(int statusCode, String reason) {
-    super.onWebSocketClose(statusCode, reason);
-
-    dedicatedServer.removeFrontendEndpoint(this);
-
-    System.out.println("Socket Closed: [" + statusCode + "] " + reason);
-    closureLatch.countDown();
-  }
-
-  @Override
-  public void onWebSocketError(Throwable cause) {
-    super.onWebSocketError(cause);
-    cause.printStackTrace(System.err);
-  }
-
-  /** send a Message to the connected FrontEnd. */
-  @Override
-  public void sendMessage(String message) {
-    try {
-      getRemote().sendString(message);
-    } catch (IOException e) {
-      e.printStackTrace();
-    }
-  }
-}

Backend/schafkopf-server/src/main/java/org/schafkopf/DedicatedServer.java

@@ -1,7 +1,11 @@
 package org.schafkopf;
 
 import jakarta.servlet.DispatcherType;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.EnumSet;
@@ -13,27 +17,50 @@ import org.eclipse.jetty.servlet.ServletContextHandler;
 import org.eclipse.jetty.servlets.CrossOriginFilter;
 import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
 
-/** Main Class that represents the Backend Server. */
+/**
+ * Main Class that represents the Backend Server.
+ */
 public class DedicatedServer {
+
   private final Server server;
   private final ServerConnector connector;
 
-  private final List<ClientConnection> clientConnections = new ArrayList<>();
+  private final List<SchafkopfClientConnection> clientConnections = new ArrayList<>();
 
   private final List<GameSession> gameSessions = new ArrayList<>();
 
-  /** Creates an Instance of the Backend Server. */
+  private GameSession currentGameSession;
+
+  /**
+   * Creates an Instance of the Backend Server.
+   */
   public DedicatedServer() {
     server = new Server();
-    InetSocketAddress address = new InetSocketAddress("localhost", 8085);
+    InetAddress address;
+
+    try (final DatagramSocket socket = new DatagramSocket()) {
+      socket.connect(InetAddress.getByName("8.8.8.8"), 10002);
+      address = socket.getLocalAddress();
+    } catch (UnknownHostException e) {
+      throw new RuntimeException(e);
+    } catch (SocketException e) {
+      throw new RuntimeException(e);
+    }
+
+    InetSocketAddress socketAddress = new InetSocketAddress(address.getHostAddress(), 8085);
+    System.out.println(
+        "Server started at: " + socketAddress.getAddress() + ":" + socketAddress.getPort());
     connector = new ServerConnector(server);
-    connector.setHost(address.getHostName());
-    connector.setPort(address.getPort());
+    connector.setHost(socketAddress.getHostName());
+    connector.setPort(socketAddress.getPort());
     server.addConnector(connector);
 
     // Setup the basic application "context" for this application at "/"
     // This is also known as the handler tree (in jetty speak)
     ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
+
+    // Add the health check servlet to the servlet context
+    context.addServlet(HealthCheckServlet.class, "/health");
     context.setContextPath("/");
     server.setHandler(context);
     // Configure CORS settings
@@ -48,9 +75,13 @@ public class DedicatedServer {
           // Add websockets
           wsContainer.addMapping("/*", new FrontendEndpointCreator(this));
         });
+
+    currentGameSession = new GameSession();
   }
 
-  /** The main entrypoint of the Application. */
+  /**
+   * The main entrypoint of the Application.
+   */
   public static void main(String[] args) throws Exception {
     DedicatedServer server = new DedicatedServer();
     server.start();
@@ -79,16 +110,23 @@ public class DedicatedServer {
     server.join();
   }
 
-  public void addFrontendEndpoint(ClientConnection endpoint) {
+  public void addFrontendEndpoint(SchafkopfClientConnection endpoint) {
     clientConnections.add(endpoint);
   }
 
-  public void removeFrontendEndpoint(ClientConnection endpoint) {
+  public void removeFrontendEndpoint(SchafkopfClientConnection endpoint) {
     clientConnections.remove(endpoint);
   }
 
-
   public void addGameSession(GameSession gameSession) {
     gameSessions.add(gameSession);
   }
+
+  public List<GameSession> getGameSessions() {
+    return gameSessions;
+  }
+
+  public GameSession getCurrentGameSession() {
+    return currentGameSession;
+  }
 }

Backend/schafkopf-server/src/main/java/org/schafkopf/FrontendEndpointCreator.java

@@ -8,6 +8,7 @@ import org.eclipse.jetty.websocket.server.JettyWebSocketCreator;
  * Creater to make new Instances of the FrontendConnection.
  */
 public class FrontendEndpointCreator implements JettyWebSocketCreator {
+
   private DedicatedServer dedicatedServer;
 
   public FrontendEndpointCreator(DedicatedServer dedicatedServer) {
@@ -18,6 +19,6 @@ public class FrontendEndpointCreator implements JettyWebSocketCreator {
   public Object createWebSocket(
       JettyServerUpgradeRequest jettyServerUpgradeRequest,
       JettyServerUpgradeResponse jettyServerUpgradeResponse) {
-    return new ClientConnection(this.dedicatedServer);
+    return new SchafkopfClientConnection(this.dedicatedServer);
   }
 }

Backend/schafkopf-server/src/main/java/org/schafkopf/GameSession.java

@@ -1,19 +1,86 @@
 package org.schafkopf;
 
-/** The main entrypoint of the Application. */
-public class GameSession {
+import java.util.ArrayList;
+import java.util.List;
+import org.schafkopf.SchafkopfException.NotEnoughPlayersException;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.player.BotPlayer;
+import org.schafkopf.player.OnlinePlayer;
+import org.schafkopf.player.Player;
+
+/**
+ * The main entrypoint of the Application.
+ */
+public class GameSession implements MessageSender {
 
   private Schafkopf schafkopf;
+  private List<Player> player;
 
-  /** The main entrypoint of the Application. */
-  public GameSession(Schafkopf schafkopf) {
-    this.schafkopf = schafkopf;
-    System.out.println("new GameSession created.");
-    startGame();
+  private List<SchafkopfClientConnection> clients;
+
+  private Thread spielThread;
+
+  /**
+   * The main entrypoint of the Application.
+   */
+  public GameSession() {
+    player = new ArrayList<>();
+    clients = new ArrayList<>();
   }
 
-  private void startGame() {
-    schafkopf.startGame();
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public void addPlayer(SchafkopfClientConnection client) {
+    if (this.player.size() >= 4) {
+      throw new RuntimeException("Game is full");
+    }
+    System.out.println("Adding player to game: " + client);
+    clients.add(client);
+
+    OnlinePlayer onlinePlayer = new OnlinePlayer(client);
+
+    this.player.add(onlinePlayer);
+
+    client.setOnlinePlayer(onlinePlayer);
   }
 
+  public Schafkopf getSchafkopf() {
+    return schafkopf;
+  }
+
+  void startGame() throws NotEnoughPlayersException {
+    int playerCount = this.player.size();
+    System.out.println("Starting game with " + playerCount + " players");
+    if (playerCount < 4) {
+      for (int i = 0; i < 4 - playerCount; i++) {
+        this.player.add(new BotPlayer());
+      }
+    }
+    System.out.println("Starting game with, now: " + this.player.size() + " players");
+
+    spielThread = new Thread(() -> {
+      try {
+        schafkopf = new Schafkopf(this.player.toArray(new Player[0]), this);
+        schafkopf.startGame();
+      } catch (NotEnoughPlayersException e) {
+        throw new RuntimeException(e);
+      } catch (InterruptedException e) {
+        throw new RuntimeException(e);
+      }
+    });
+
+    spielThread.start();
+
+    //    schafkopf = new Schafkopf(this.player.toArray(new Player[0]), this);
+
+  }
+
+  @Override
+  public void sendMessage(SchafkopfBaseMessage message) {
+    System.out.println("Sending message to Client: " + message);
+    for (SchafkopfClientConnection client : clients) {
+      client.sendMessage(message);
+    }
+  }
 }

Backend/schafkopf-server/src/main/java/org/schafkopf/HealthCheckServlet.java

@@ -0,0 +1,23 @@
+package org.schafkopf;
+
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public class HealthCheckServlet extends HttpServlet {
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
+      throws ServletException, IOException {
+    resp.setContentType("text/plain");
+    resp.getWriter().println("Backend server is up and running!");
+  }
+}

Backend/schafkopf-server/src/main/java/org/schafkopf/SchafkopfClientConnection.java

@@ -0,0 +1,134 @@
+package org.schafkopf;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.WebSocketAdapter;
+import org.schafkopf.SchafkopfException.NotEnoughPlayersException;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageOrigin;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageType;
+import org.schafkopf.karte.Karte;
+import org.schafkopf.player.OnlinePlayer;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public class SchafkopfClientConnection extends WebSocketAdapter implements MessageSender {
+
+  private final CountDownLatch connectionLatch;
+  private final CountDownLatch closureLatch = new CountDownLatch(1);
+  private DedicatedServer dedicatedServer;
+
+  private GameSession gameSession;
+
+  private Session session;
+
+  private OnlinePlayer onlinePlayer;
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public SchafkopfClientConnection(DedicatedServer dedicatedServer) {
+    this.dedicatedServer = dedicatedServer;
+    this.connectionLatch = new CountDownLatch(1);
+    System.out.println("new ClientConnection created.");
+  }
+
+  @Override
+  public void onWebSocketConnect(Session session) {
+    this.session = session;
+    super.onWebSocketConnect(session);
+    String clientIp = session.getRemoteAddress().toString();
+    System.out.println("Endpoint connected from ip: " + clientIp);
+
+    connectionLatch.countDown();
+    dedicatedServer.addFrontendEndpoint(this);
+    sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.SERVER_CONNECTION_SUCCESSFUL));
+  }
+
+  @Override
+  public void onWebSocketText(String jsonMessage) {
+    super.onWebSocketText(jsonMessage);
+    Gson gson = new Gson();
+    JsonObject jsonObject = gson.fromJson(jsonMessage, JsonObject.class);
+    // Check if the origin is "frontend"
+    String origin = jsonObject.get("origin").getAsString();
+    if (SchafkopfMessageOrigin.BACKEND.toString().equals(origin)) {
+      JsonObject message = jsonObject.getAsJsonObject("message");
+      JsonObject content = message.getAsJsonObject("content");
+      String messageType = message.get("message_type").getAsString();
+      if ("HEARTBEAT_SYN".equals(messageType)) {
+
+        sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.HEARTBEAT_ACK));
+        return;
+      } else if (SchafkopfMessageType.JOIN_GAME.toString().equals(messageType)) {
+
+        gameSession = dedicatedServer.getCurrentGameSession();
+        dedicatedServer.getCurrentGameSession().addPlayer(this);
+
+      } else if ("START_GAME".equals(messageType)) {
+
+        System.out.println("Received START_GAME message from " + session.getRemoteAddress() + ".");
+        try {
+          dedicatedServer.getCurrentGameSession().startGame();
+        } catch (NotEnoughPlayersException e) {
+
+          sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.UNKNOWN_ERROR,
+              "Not enough players to start the game."));
+
+        }
+
+      } else if (SchafkopfMessageType.PLAYER_CARD.toString().equals(messageType)) {
+
+        onlinePlayer.receiveCard(Karte.valueOf(content.get("card").getAsString()));
+
+      } else if ("list_online_games".equals(messageType)) {
+        System.out.println(
+            "Received list_online_games message from " + session.getRemoteAddress() + ".");
+      }
+
+      System.out.println(
+          "Received  message from Client " + session.getRemoteAddress() + " " + jsonMessage);
+    }
+  }
+
+
+  public void setOnlinePlayer(OnlinePlayer onlinePlayer) {
+    this.onlinePlayer = onlinePlayer;
+  }
+
+  @Override
+  public void onWebSocketClose(int statusCode, String reason) {
+    super.onWebSocketClose(statusCode, reason);
+
+    dedicatedServer.removeFrontendEndpoint(this);
+
+    System.out.println("Socket Closed: [" + statusCode + "] " + reason);
+    closureLatch.countDown();
+  }
+
+  @Override
+  public void onWebSocketError(Throwable cause) {
+    super.onWebSocketError(cause);
+    cause.printStackTrace(System.err);
+  }
+
+  /**
+   * Send a message to the connected FrontEnd.
+   */
+  @Override
+  public void sendMessage(SchafkopfBaseMessage message) {
+    SchafkopfMessage schafkopfMessage = new SchafkopfMessage(
+        SchafkopfMessageOrigin.DEDICATED_SERVER,
+        message);
+    System.out.println("Sending message to Client: " + schafkopfMessage.getMessageAsString());
+    try {
+      getRemote().sendString(schafkopfMessage.getMessageAsString());
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+  }
+}

Backend/schafkopf-shared/src/main/java/org/schafkopf/GameState.java

@@ -5,14 +5,18 @@ import com.google.gson.JsonObject;
 import org.schafkopf.karte.Karte;
 import org.schafkopf.karte.KartenFarbe;
 
-/** GameState. */
+/**
+ * GameState.
+ */
 public class GameState {
 
   public GamePhase getGamePhase() {
     return this.gamePhase;
   }
 
-  /** GamePhase. */
+  /**
+   * GamePhase.
+   */
   public enum GamePhase {
     CHOOSE_GAME("Spiel muss gewählt werden"),
 
@@ -53,7 +57,9 @@ public class GameState {
     this.currentPlayer = player;
   }
 
-  /** GameState. */
+  /**
+   * GameState.
+   */
   public GameState(GamePhase phase, Integer player, Karte card, KartenFarbe color, boolean trumpf) {
     this.gamePhase = phase;
     this.currentPlayer = player;
@@ -62,19 +68,34 @@ public class GameState {
     this.trumpf = trumpf;
   }
 
-  /** GameState. */
+  /**
+   * GameState.
+   */
   public GameState(GamePhase phase, Integer player, Karte card) {
     this.gamePhase = phase;
     this.currentPlayer = player;
     this.card = card;
   }
 
-  /** GameState. */
+  /**
+   * GameState.
+   */
   public JsonObject getJson() {
     Gson gson = new Gson();
-    JsonObject jsonObject = new JsonObject();
-    jsonObject.add("gamestate", gson.toJsonTree(this));
+    JsonObject gameStateObject = new JsonObject();
 
-    return jsonObject;
+    if (this.currentPlayer != null) {
+      gameStateObject.addProperty("currentPlayer", this.currentPlayer);
+    }
+    if (this.card != null) {
+      gameStateObject.add("card", gson.toJsonTree(this.card));
+    }
+    gameStateObject.addProperty("gamePhase", this.gamePhase.name());
+    gameStateObject.addProperty("trumpf", this.trumpf);
+    if (this.color != null) {
+      gameStateObject.addProperty("color", this.color.name());
+    }
+
+    return gameStateObject;
   }
 }

Backend/schafkopf-shared/src/main/java/org/schafkopf/MessageListener.java

@@ -0,0 +1,9 @@
+package org.schafkopf;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public interface MessageListener {
+
+  void receiveMessage(String message);
+}

Backend/schafkopf-shared/src/main/java/org/schafkopf/MessageSender.java

@@ -1,6 +1,11 @@
 package org.schafkopf;
 
-/** The main entrypoint of the Application. */
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+
+/**
+ * The main entrypoint of the Application.
+ */
 public interface MessageSender {
-  void sendMessage(String message);
+
+  void sendMessage(SchafkopfBaseMessage message);
 }

Backend/schafkopf-shared/src/main/java/org/schafkopf/Schafkopf.java

@@ -1,25 +1,31 @@
 package org.schafkopf;
 
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
 import org.schafkopf.GameState.GamePhase;
+import org.schafkopf.SchafkopfException.NotEnoughPlayersException;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageType;
 import org.schafkopf.karte.Karte;
 import org.schafkopf.karte.KartenFarbe;
 import org.schafkopf.karte.KartenListe;
 import org.schafkopf.karte.KartenUtil;
 import org.schafkopf.player.BotPlayer;
+import org.schafkopf.player.OnlinePlayer;
 import org.schafkopf.player.Player;
-import org.schafkopf.spielcontroller.FarbGeierController;
-import org.schafkopf.spielcontroller.FarbSoloController;
-import org.schafkopf.spielcontroller.FarbWenzController;
-import org.schafkopf.spielcontroller.GeierController;
 import org.schafkopf.spielcontroller.SauSpielController;
 import org.schafkopf.spielcontroller.SpielController;
-import org.schafkopf.spielcontroller.WenzController;
 
-/** The main class representing the Schafkopf game. */
+/**
+ * The main class representing the Schafkopf game.
+ */
 public class Schafkopf {
+
   private final MessageSender messageSender;
 
-  /** The game controller. This is the class that implements the game logic. */
+  /**
+   * The game controller. This is the class that implements the game logic.
+   */
   private SpielController spiel = new SauSpielController(0, KartenFarbe.EICHEL);
 
   private final Player[] player;
@@ -32,8 +38,13 @@ public class Schafkopf {
    *
    * @param messageSender MessageSender
    */
-  public Schafkopf(Player[] player, MessageSender messageSender) {
+  public Schafkopf(Player[] player, MessageSender messageSender) throws NotEnoughPlayersException {
     this.player = player;
+
+    if (player.length < 4) {
+      throw new NotEnoughPlayersException();
+    }
+
     this.messageSender = messageSender;
     System.out.println("SchaffKopfGame erstellt");
   }
@@ -42,23 +53,24 @@ public class Schafkopf {
     return player;
   }
 
-  /** Set GameState to "started" and start Game Thread. */
-  public void startGame() {
+  /**
+   * Set GameState to "started" and start Game Thread.
+   */
+  public void startGame() throws InterruptedException {
     if (gameState.getGamePhase() != GamePhase.GAME_STOP) {
       System.out.println("Game already started!");
-      messageSender.sendMessage("Game already started!");
+      messageSender.sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.UNKNOWN_ERROR));
     } else {
       gameState = new GameState(GamePhase.GAME_START);
       setAndSendGameState(gameState);
       System.out.println("Start Game");
 
       KartenListe austeilen = KartenUtil.initializeSchafKopfCardDeck();
+      austeilen.shuffle();
       for (Player currentPlayer : player) {
         if (currentPlayer instanceof BotPlayer botPlayer) {
           KartenListe botHand = new KartenListe();
           for (int i = 7; i >= 0; i--) {
-            System.out.println("Austeilen: " + austeilen.size());
-            System.out.println("Bot Hand: " + i);
             botHand.addKarten(austeilen.removeKarten(austeilen.getByIndex(i)));
           }
           System.out.println("Bot Hand: " + botHand.getJson().toString());
@@ -66,17 +78,35 @@ public class Schafkopf {
         }
       }
 
-      spielThread = new Thread(() -> new Spielablauf(this, spiel));
+      for (Player currentPlayer : player) {
+        if (currentPlayer instanceof OnlinePlayer) {
+          Karte[] karten = new Karte[8];
+          for (int i = 7; i >= 0; i--) {
+            karten[i] = austeilen.removeKarten(austeilen.getByIndex(i));
+          }
+          Gson gson = new Gson();
+          JsonObject messageObject = new JsonObject();
+          messageObject.add("cards", gson.toJsonTree(karten));
 
-      spielThread.start();
+          messageSender.sendMessage(
+              new SchafkopfBaseMessage(SchafkopfMessageType.ONLINE_PLAYER_HAND, messageObject));
+        }
+      }
+
+      //      spielThread = new Thread(() -> new Spielablauf(this, spiel));
+      //
+      //      spielThread.start();
+      new Spielablauf(this, spiel);
     }
   }
 
-  /** Set GameState to "stopped" and interrupt Game Thread. */
+  /**
+   * Set GameState to "stopped" and interrupt Game Thread.
+   */
   public void stopGame() {
     if (gameState.getGamePhase() == GamePhase.GAME_STOP) {
       System.out.println("no active Game!");
-      messageSender.sendMessage("no active Game!");
+      messageSender.sendMessage(new SchafkopfBaseMessage(SchafkopfMessageType.UNKNOWN_ERROR));
     } else {
       gameState = new GameState(GamePhase.GAME_STOP);
       setAndSendGameState(gameState);
@@ -85,68 +115,13 @@ public class Schafkopf {
     spielThread.interrupt();
   }
 
-  /** Set GameType. */
-  public void setGame(String message) {
-    System.out.println("Set Game: " + message);
-    messageSender.sendMessage("Set Game: " + message);
-    switch (message) {
-      case "setgame:herzsolo":
-        this.spiel = new FarbSoloController(0, KartenFarbe.HERZ);
-        break;
-      case "setgame:blattsolo":
-        this.spiel = new FarbSoloController(0, KartenFarbe.BLATT);
-        break;
-      case "setgame:eichelsolo":
-        this.spiel = new FarbSoloController(0, KartenFarbe.EICHEL);
-        break;
-      case "setgame:schellsolo":
-        this.spiel = new FarbSoloController(0, KartenFarbe.SCHELL);
-        break;
-
-      case "setgame:wenz":
-        this.spiel = new WenzController(0);
-        break;
-      case "setgame:geier":
-        this.spiel = new GeierController(0);
-        break;
-
-      case "setgame:eichelwenz":
-        this.spiel = new FarbWenzController(0, KartenFarbe.EICHEL);
-        break;
-      case "setgame:herzwenz":
-        this.spiel = new FarbWenzController(0, KartenFarbe.HERZ);
-        break;
-      case "setgame:blattwenz":
-        this.spiel = new FarbWenzController(0, KartenFarbe.BLATT);
-        break;
-      case "setgame:schellwenz":
-        this.spiel = new FarbWenzController(0, KartenFarbe.SCHELL);
-        break;
-
-      case "setgame:eichelgeier":
-        this.spiel = new FarbGeierController(0, KartenFarbe.EICHEL);
-        break;
-      case "setgame:herzgeier":
-        this.spiel = new FarbGeierController(0, KartenFarbe.HERZ);
-        break;
-      case "setgame:blattgeier":
-        this.spiel = new FarbGeierController(0, KartenFarbe.BLATT);
-        break;
-      case "setgame:schellgeier":
-        this.spiel = new FarbGeierController(0, KartenFarbe.SCHELL);
-        break;
-
-      case "setgame:sauspiel":
-        this.spiel = new SauSpielController(0, KartenFarbe.EICHEL);
-        break;
-      default:
-        System.out.println("Ungültiges Spiel");
-    }
-  }
-
+  /**
+   * Class that represents one Frontend Connection.
+   */
   public void setAndSendGameState(GameState gameState) {
     this.gameState = gameState;
-    this.messageSender.sendMessage(this.gameState.getJson().toString());
+    this.messageSender.sendMessage(
+        new SchafkopfBaseMessage(SchafkopfMessageType.GAME_STATE, gameState.getJson()));
   }
 
   public GameState getGameState() {

Backend/schafkopf-shared/src/main/java/org/schafkopf/SchafkopfException.java

@@ -0,0 +1,37 @@
+package org.schafkopf;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public class SchafkopfException extends Exception {
+
+  private SchafkopfException(String message) {
+    super(message);
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public static class NotEnoughPlayersException extends SchafkopfException {
+
+    public NotEnoughPlayersException() {
+      super("Not enough players to start the game");
+    }
+
+    // You can also include additional constructors or methods if needed
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public class InvalidMoveException extends SchafkopfException {
+
+    // Constructor with a message
+    public InvalidMoveException(String message) {
+      super(message);
+    }
+
+    // You can also include additional constructors or methods if needed
+  }
+}
+

Backend/schafkopf-shared/src/main/java/org/schafkopf/SchafkopfMessage.java

@@ -0,0 +1,141 @@
+package org.schafkopf;
+
+import com.google.gson.JsonObject;
+
+/**
+ * Class that represents one Frontend Connection.
+ */
+public class SchafkopfMessage {
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public static class SchafkopfBaseMessage {
+
+    private JsonObject message;
+
+    public SchafkopfBaseMessage(SchafkopfMessageType messageType, String content) {
+      this.message = buildBaseMessage(messageType, content);
+    }
+
+    public SchafkopfBaseMessage(SchafkopfMessageType messageType, JsonObject content) {
+      this.message = buildBaseMessage(messageType, content);
+    }
+
+    public SchafkopfBaseMessage(SchafkopfMessageType messageType) {
+      this.message = buildBaseMessage(messageType);
+    }
+
+    public JsonObject getBaseMessage() {
+      return message;
+    }
+  }
+
+  JsonObject message;
+
+  public SchafkopfMessage(SchafkopfMessageOrigin origin, SchafkopfBaseMessage baseMessage) {
+    this.message = buildWrapperMessage(origin, baseMessage.getBaseMessage());
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public SchafkopfMessage(SchafkopfMessageOrigin origin, SchafkopfMessageType messageType) {
+
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.add("content", buildBaseMessage(messageType));
+
+    this.message = buildWrapperMessage(origin, messageContentObject);
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  private SchafkopfMessage(SchafkopfMessageOrigin origin, SchafkopfMessageType messageType,
+      JsonObject messageContent) {
+
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.add("content", buildBaseMessage(messageType, messageContent));
+
+    this.message = buildWrapperMessage(origin, messageContentObject);
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public SchafkopfMessage(SchafkopfMessageOrigin origin, SchafkopfMessageType messageType,
+      String messageContent) {
+
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.add("content", buildBaseMessage(messageType, messageContent));
+
+    this.message = buildWrapperMessage(origin, messageContentObject);
+  }
+
+  private static JsonObject buildWrapperMessage(SchafkopfMessageOrigin origin, JsonObject message) {
+    JsonObject messageObject = new JsonObject();
+    messageObject.addProperty("origin", origin.toString());
+    messageObject.add("message", message);
+
+    return messageObject;
+  }
+
+  private static JsonObject buildBaseMessage(SchafkopfMessageType messageType,
+      String messageContent) {
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.addProperty("message_type", messageType.toString());
+    messageContentObject.addProperty("content", messageContent);
+
+    return messageContentObject;
+  }
+
+  private static JsonObject buildBaseMessage(SchafkopfMessageType messageType,
+      JsonObject messageContent) {
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.addProperty("message_type", messageType.toString());
+    messageContentObject.add("content", messageContent);
+
+    return messageContentObject;
+  }
+
+  private static JsonObject buildBaseMessage(SchafkopfMessageType messageType) {
+    JsonObject messageContentObject = new JsonObject();
+    messageContentObject.addProperty("message_type", messageType.toString());
+
+    return messageContentObject;
+  }
+
+  public JsonObject getMessage() {
+    return message;
+  }
+
+  public String getMessageAsString() {
+    return message.toString();
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public enum SchafkopfMessageType {
+    UNKNOWN_ERROR,
+    HEARTBEAT_SYN,
+    HEARTBEAT_ACK,
+    GET_CARD_ONLINE_PLAYER,
+    ONLINE_PLAYER_HAND,
+    GAME_STATE,
+    SERVER_CONNECTION_SUCCESSFUL,
+    REQUEST_SERVER_CONNECTION,
+    START_GAME,
+    JOIN_GAME,
+    PLAYER_CARD
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public enum SchafkopfMessageOrigin {
+    FRONTEND,
+    BACKEND,
+    DEDICATED_SERVER
+  }
+}

Backend/schafkopf-shared/src/main/java/org/schafkopf/Spielablauf.java

@@ -8,7 +8,9 @@ import org.schafkopf.spielcontroller.SpielController;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-/** The main class that controlls the game flow. */
+/**
+ * The main class that controlls the game flow.
+ */
 public class Spielablauf {
 
   private static final Logger logger = LoggerFactory.getLogger(Spielablauf.class);
@@ -22,7 +24,7 @@ public class Spielablauf {
 
   private final Schafkopf schafkopf;
 
-  Spielablauf(Schafkopf schafkopf, SpielController spiel) {
+  Spielablauf(Schafkopf schafkopf, SpielController spiel) throws InterruptedException {
     this.schafkopf = schafkopf;
     this.spiel = spiel;
     this.players = schafkopf.getPlayer();
@@ -30,7 +32,7 @@ public class Spielablauf {
     playRound();
   }
 
-  private void playRound() {
+  private void playRound() throws InterruptedException {
     int startingPlayer = 0;
 
     logger.info("Starte Stiche");
@@ -41,7 +43,7 @@ public class Spielablauf {
     schafkopf.stopGame();
   }
 
-  private int playTrick(int startingPlayer) {
+  private int playTrick(int startingPlayer) throws InterruptedException {
     schafkopf.setAndSendGameState(new GameState(GamePhase.TRICK_START));
 
     for (int i = 0; i < 4; i++) {

Backend/schafkopf-shared/src/main/java/org/schafkopf/karte/KartenListe.java

@@ -3,12 +3,14 @@ package org.schafkopf.karte;
 import com.google.gson.Gson;
 import com.google.gson.JsonObject;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
  * A Class that represents a list of Cards.
  */
 public class KartenListe {
+
   private List<Karte> kartenListe;
 
   public KartenListe() {
@@ -23,6 +25,10 @@ public class KartenListe {
     return this.kartenListe;
   }
 
+  public void shuffle() {
+    Collections.shuffle(this.kartenListe);
+  }
+
   /**
    * A Class that represents a list of Cards.
    */
@@ -158,6 +164,24 @@ public class KartenListe {
     return result;
   }
 
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public Karte getKarten(KartenSymbol symbol, KartenFarbe farbe) {
+    KartenListe result = new KartenListe();
+    for (Karte karte : this.kartenListe) {
+      if (karte.getSymbol().equals(symbol)) {
+        result.addKarten(karte);
+      }
+    }
+    for (Karte karte : result.kartenListe) {
+      if (karte.getFarbe().equals(farbe)) {
+        result.addKarten(karte);
+      }
+    }
+    return result.getByIndex(0);
+  }
+
   /**
    * A Class that represents a list of Cards.
    */

Backend/schafkopf-shared/src/main/java/org/schafkopf/player/OnlinePlayer.java

@@ -0,0 +1,46 @@
+package org.schafkopf.player;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import org.schafkopf.MessageSender;
+import org.schafkopf.SchafkopfMessage.SchafkopfBaseMessage;
+import org.schafkopf.SchafkopfMessage.SchafkopfMessageType;
+import org.schafkopf.karte.Karte;
+import org.schafkopf.karte.KartenListe;
+import org.schafkopf.spielcontroller.SpielController;
+
+/**
+ * Player that plays in real life.
+ */
+public class OnlinePlayer extends Player {
+
+  private final MessageSender messageSender;
+  private final BlockingQueue<Karte> receivedCardQueue = new LinkedBlockingQueue<>();
+
+  public OnlinePlayer(MessageSender messageSender) {
+    this.messageSender = messageSender;
+  }
+
+  @Override
+  public Karte play(SpielController spiel, KartenListe tischKarten, KartenListe gespielteKarten)
+      throws InterruptedException {
+    Karte spielKarte = null;
+
+    // Send the message to request the card from the frontend
+    messageSender.sendMessage(
+        new SchafkopfBaseMessage(SchafkopfMessageType.GET_CARD_ONLINE_PLAYER));
+
+    spielKarte = receivedCardQueue.take();
+
+    System.out.println("Karte gespielt: " + spielKarte);
+    return spielKarte;
+  }
+
+  /**
+   * Class that represents one Frontend Connection.
+   */
+  public void receiveCard(Karte receivedCard) {
+    System.out.println("Received Card before Queue: " + receivedCard.getName());
+    receivedCardQueue.add(receivedCard);
+  }
+}

Backend/schafkopf-shared/src/main/java/org/schafkopf/player/Player.java

@@ -4,8 +4,12 @@ import org.schafkopf.karte.Karte;
 import org.schafkopf.karte.KartenListe;
 import org.schafkopf.spielcontroller.SpielController;
 
-/** Class that represents one Player of the game. */
+/**
+ * Class that represents one Player of the game.
+ */
 public abstract class Player {
+
   public abstract Karte play(
-      SpielController spiel, KartenListe tischKarten, KartenListe gespielteKarten);
+      SpielController spiel, KartenListe tischKarten, KartenListe gespielteKarten)
+      throws InterruptedException;
 }