fixed #49

clean up

client/src/main/java/ch/zhaw/pm2/multichat/client/ChatWindowController.java

@@ -1,9 +1,12 @@
 package ch.zhaw.pm2.multichat.client;
 
-import ch.zhaw.pm2.multichat.client.ClientConnectionHandler.State;
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler;
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State;
 import ch.zhaw.pm2.multichat.protocol.ChatProtocolException;
-import ch.zhaw.pm2.multichat.protocol.NetworkHandler;
+import ch.zhaw.pm2.multichat.protocol.Message;
 import javafx.application.Platform;
+import javafx.beans.value.ChangeListener;
+import javafx.beans.value.ObservableValue;
 import javafx.event.EventHandler;
 import javafx.fxml.FXML;
 import javafx.scene.control.Button;
@@ -13,122 +16,162 @@ import javafx.scene.layout.Pane;
 import javafx.stage.WindowEvent;
 
 import java.io.IOException;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
-import static ch.zhaw.pm2.multichat.client.ClientConnectionHandler.State.*;
+import static ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State.*;
 
+/**
+ * Class Representing the Controller Element of the Window, also Contains the Elements that contacts the View Elements via
+ * Listeners and Observable Objects.
+ * To Contact the Model Elements needed it also holds references to message and the Connectionhandler.
+ */
 public class ChatWindowController {
-    private final Pattern messagePattern = Pattern.compile( "^(?:@(\\w*))?\\s*(.*)$" );
     private ClientConnectionHandler connectionHandler;
     private ClientMessageList messages;
-
     private final WindowCloseHandler windowCloseHandler = new WindowCloseHandler();
 
-    @FXML private Pane rootPane;
-    @FXML private TextField serverAddressField;
-    @FXML private TextField serverPortField;
-    @FXML private TextField userNameField;
-    @FXML private TextField messageField;
-    @FXML private TextArea messageArea;
-    @FXML private Button connectButton;
-    @FXML private Button sendButton;
-    @FXML private TextField filterValue;
-
-
     @FXML
-    public void initialize() {
+    private Pane rootPane;
-        serverAddressField.setText(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
+    @FXML
-        serverPortField.setText(String.valueOf(NetworkHandler.DEFAULT_PORT));
+    private TextField serverAddressField;
-        stateChanged(NEW);
+    @FXML
-        messages = new ClientMessageList(this);
+    private TextField serverPortField;
+    @FXML
+    private TextField userNameField;
+    @FXML
+    private TextField messageField;
+    @FXML
+    private TextArea messageArea;
+    @FXML
+    private Button connectButton;
+    @FXML
+    private TextField filterValue;
+    @FXML
+    private Button sendButton;
+
+
+    /**
+     * Takes a message object and stores it used as Model and also starts message Listener via messageListener method.
+     *
+     * @param messages Object that will be set for use as Model
+     */
+    public void setMessages(ClientMessageList messages) {
+        this.messages = messages;
+        messageListener();
     }
 
+    /**
+     * Takes a Connection handler object and stores it used as Model and also starts a Listener for it.
+     *
+     * @param connectionHandler that will be set and used as Model.
+     */
+    public void setConnectionHandler(ClientConnectionHandler connectionHandler) {
+        this.connectionHandler = connectionHandler;
+        startConnectionHandlerListener();
+        serverAddressField.setText(connectionHandler.getServerAddressProperty().get());
+        serverPortField.setText(String.valueOf(connectionHandler.getServerPortProperty().get()));
+    }
+
+    /**
+     * Method which closes the Application via use of the disconnect Method.
+     */
     private void applicationClose() {
-        connectionHandler.setState(DISCONNECTED);
+        disconnect();
     }
 
+    /**
+     * Method that handles the Connect Button and Initiates connect when connectionHandler is not Connected or
+     * a disconnect when it is connected.
+     */
     @FXML
-    private void toggleConnection () {
+    private void toggleConnection() {
-        if (connectionHandler == null || connectionHandler.getState() != CONNECTED) {
+        if (connectionHandler == null || connectionHandler.getStateProperty().get() != CONNECTED) {
             connect();
         } else {
             disconnect();
         }
     }
 
+    /**
+     * Initiates a connection by starting Connection Handler and telling, the Handler to start a connection.
+     */
     private void connect() {
         try {
-            messages = new ClientMessageList(this); // clear message list
+            messages.clear(); // clear message list
             startConnectionHandler();
             connectionHandler.connect();
-        } catch(ChatProtocolException | IOException e) {
+        } catch (ChatProtocolException | IOException e) {
-            writeError(e.getMessage());
+            addError("Error while starting Connection Handler and connect" + e);
         }
     }
 
+    /**
+     * Initiates disconnecting of the connectionHandler, also checks if connectionHandler is available.
+     */
     private void disconnect() {
         if (connectionHandler == null) {
-            writeError("No connection handler");
+            addError("No connection handler");
             return;
         }
         try {
             connectionHandler.disconnect();
         } catch (ChatProtocolException e) {
-            writeError(e.getMessage());
+            addError(e.getMessage());
         }
     }
 
+    /**
+     * Method which is used when the send button is pressed and handing over a message to the Connection Handler
+     */
     @FXML
     private void message() {
-        if (connectionHandler == null) {
-            writeError("No connection handler");
-            return;
-        }
         String messageString = messageField.getText().strip();
-        messageField.clear();
-        Matcher matcher = messagePattern.matcher(messageString);
-        if (matcher.find()) {
-            String receiver = matcher.group(1);
-            String message = matcher.group(2);
-            if (receiver == null || receiver.isBlank()) receiver = ClientConnectionHandler.USER_ALL;
         try {
-                connectionHandler.message(receiver, message);
+            if (connectionHandler == null) {
-            } catch (ChatProtocolException e) {
+                addError("No connection handler");
-                writeError(e.getMessage());
+            } else if (!connectionHandler.message(messageString)) {
-            }
+                addError("Not a valid message format.");
             } else {
-            writeError("Not a valid message format.");
+                messageField.clear();
+            }
+        } catch (ChatProtocolException e) {
+            addError(e.getMessage());
         }
     }
 
+    /**
+     * Method which is used when a Filter is applied
+     * Setting the Text in the message area after sending it through the filter.
+     */
     @FXML
-    private void applyFilter( ) {
+    private void applyFilter() {
-    	this.redrawMessageList();
+        Platform.runLater(() -> this.messageArea.setText(messages.getFilteredMessages(filterValue.getText().strip())));
     }
 
+    /**
+     * Starts the ConnectionHandler setting the username and Checking if the name follows the valid format of no spaces.
+     *
+     * @throws IOException for error that may occur during initialization of connectionHandler.
+     */
     private void startConnectionHandler() throws IOException {
         String userName = userNameField.getText();
+        if (!userName.contains(" ")) {
             String serverAddress = serverAddressField.getText();
             int serverPort = Integer.parseInt(serverPortField.getText());
-        connectionHandler = new ClientConnectionHandler(
+            connectionHandler.initialize(serverAddress, serverPort, userName);
-            NetworkHandler.openConnection(serverAddress, serverPort), userName,
-            this);
             new Thread(connectionHandler).start();
 
-        // register window close handler
             rootPane.getScene().getWindow().addEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
-    }
+        } else {
-
+            addError("It is not allowed to have spaces in username!");
-    private void terminateConnectionHandler() {
-        // unregister window close handler
-        rootPane.getScene().getWindow().removeEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
-        if (connectionHandler != null) {
-            connectionHandler.stopReceiving();
-            connectionHandler = null;
         }
     }
 
+    /**
+     * Sets the state shown according to the state the method receives, if state indicates disconnected it will also inform the
+     * Connection Handler and tell it to stop Receiving more messages.
+     *
+     * @param newState is the state that it should be set to.
+     */
     public void stateChanged(State newState) {
         // update UI (need to be run in UI thread: see Platform.runLater())
         Platform.runLater(new Runnable() {
@@ -138,10 +181,15 @@ public class ChatWindowController {
             }
         });
         if (newState == DISCONNECTED) {
-            terminateConnectionHandler();
+            connectionHandler.stopReceiving();
         }
     }
 
+    /**
+     * Sets displayed username according to the String provided.
+     *
+     * @param userName provided String that is set as name.
+     */
     public void setUserName(String userName) {
         Platform.runLater(new Runnable() {
             @Override
@@ -151,6 +199,11 @@ public class ChatWindowController {
         });
     }
 
+    /**
+     * Sets displayed Server Address.
+     *
+     * @param serverAddress provided String that is set as server address.
+     */
     public void setServerAddress(String serverAddress) {
         Platform.runLater(new Runnable() {
             @Override
@@ -160,6 +213,11 @@ public class ChatWindowController {
         });
     }
 
+    /**
+     * Sets displayed Server port.
+     *
+     * @param serverPort provided String that is set as server port.
+     */
     public void setServerPort(int serverPort) {
         Platform.runLater(new Runnable() {
             @Override
@@ -169,51 +227,71 @@ public class ChatWindowController {
         });
     }
 
-    public void addMessage(String sender, String receiver, String message) {
+    /**
-        messages.addMessage(ClientMessageList.MessageType.MESSAGE, sender, receiver, message);
+     * Method which adds an incoming String as an Error Message.
-        this.redrawMessageList();
+     *
-    }
+     * @param message String to be added as Error
-
+     */
-    public void addInfo(String message) {
-        messages.addMessage(ClientMessageList.MessageType.INFO, null, null, message);
-        this.redrawMessageList();
-    }
-
     public void addError(String message) {
-        messages.addMessage(ClientMessageList.MessageType.ERROR, null, null, message);
+        messages.addMessage(new Message(ConnectionHandler.DATA_TYPE.DATA_TYPE_ERROR, null, null, message));
-        this.redrawMessageList();
     }
 
-    public void clearMessageArea() {
+    /**
-        this.messageArea.clear();
+     * Nested Class in charge of Closing the window
-    }
+     */
-
-
-    private void redrawMessageList() {
-        Platform.runLater(() -> messages.writeFilteredMessages(filterValue.getText().strip()));
-    }
-
-    public void writeError(String message) {
-        this.messageArea.appendText(String.format("[ERROR] %s\n", message));
-    }
-
-    public void writeInfo(String message) {
-        this.messageArea.appendText(String.format("[INFO] %s\n", message));
-    }
-
-    public void writeMessage(String sender, String reciever, String message) {
-        this.messageArea.appendText(String.format("[%s -> %s] %s\n", sender, reciever, message));
-    }
-
-
     class WindowCloseHandler implements EventHandler<WindowEvent> {
+
+        /**
+         * @param event the event which occurred when Windows is closed
+         */
         public void handle(WindowEvent event) {
             applicationClose();
         }
-
     }
 
+    /**
+     * Starts several new Listener for Connection Handler changes by using several observable properties.
+     */
+    public void startConnectionHandlerListener() {
+        connectionHandler.getStateProperty().addListener(new ChangeListener<State>() {
+            @Override
+            public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
+                stateChanged(newValue);
+            }
+        });
 
+        connectionHandler.getUserNameProperty().addListener(new ChangeListener<String>() {
+            @Override
+            public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
+                setUserName(newValue);
+            }
+        });
 
+        connectionHandler.getServerAddressProperty().addListener(new ChangeListener<String>() {
+            @Override
+            public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
+                setServerAddress(newValue);
+            }
+        });
+
+        connectionHandler.getServerPortProperty().addListener(new ChangeListener<Number>() {
+            @Override
+            public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
+                setServerPort(newValue.intValue());
+            }
+        });
+    }
+
+    /**
+     * Starts a new Listener for messages by using the observable Boolean.
+     */
+    private void messageListener() {
+        messages.getChangedProperty().addListener(new ChangeListener<Boolean>() {
+            @Override
+            public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
+                Platform.runLater(() -> messageArea.setText(messages.getFilteredMessages(filterValue.getText().strip())));
+            }
+        });
+    }
 
 }

client/src/main/java/ch/zhaw/pm2/multichat/client/Client.java

@@ -2,8 +2,16 @@ package ch.zhaw.pm2.multichat.client;
 
 import javafx.application.Application;
 
+/**
+ * Client Main Class in charge of starting the UI only contains main method.
+ */
 public class Client {
 
+    /**
+     * Main method which launches the Client UI
+     *
+     * @param args no arguments needed
+     */
     public static void main(String[] args) {
         // Start UI
         System.out.println("Starting Client Application");

client/src/main/java/ch/zhaw/pm2/multichat/client/ClientConnectionHandler.java

@@ -1,66 +1,132 @@
 package ch.zhaw.pm2.multichat.client;
 
 import ch.zhaw.pm2.multichat.protocol.ChatProtocolException;
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler;
+import ch.zhaw.pm2.multichat.protocol.Message;
 import ch.zhaw.pm2.multichat.protocol.NetworkHandler;
+import javafx.beans.property.SimpleIntegerProperty;
+import javafx.beans.property.SimpleObjectProperty;
+import javafx.beans.property.SimpleStringProperty;
 
 import java.io.EOFException;
 import java.io.IOException;
 import java.net.SocketException;
 import java.util.Scanner;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
-import static ch.zhaw.pm2.multichat.client.ClientConnectionHandler.State.*;
+import static ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State.*;
 
-public class ClientConnectionHandler implements Runnable {
+/**
-    private final NetworkHandler.NetworkConnection<String> connection;
+ * Client Connection Handler Class is used for the connection of the Client to a server
-    private final ChatWindowController controller;
+ * it is used part as a Model storing properties like userName, state, serverAddress and Port.
+ * Also holds methods to
+ */
+public class ClientConnectionHandler extends ConnectionHandler implements Runnable {
 
-    // Data types used for the Chat Protocol
+    private final Pattern messagePattern = Pattern.compile("^(?:@(\\S*))?\\s*(.*)$");
-    private static final String DATA_TYPE_CONNECT = "CONNECT";
-    private static final String DATA_TYPE_CONFIRM = "CONFIRM";
-    private static final String DATA_TYPE_DISCONNECT = "DISCONNECT";
-    private static final String DATA_TYPE_MESSAGE = "MESSAGE";
-    private static final String DATA_TYPE_ERROR = "ERROR";
 
-    public static final String USER_NONE = "";
+    private final SimpleStringProperty userName;
-    public static final String USER_ALL = "*";
+    private final SimpleObjectProperty<State> state;
+    private final ClientMessageList messages;
+    private final SimpleStringProperty serverAddress;
+    private final SimpleIntegerProperty serverPort;
 
-    private String userName = USER_NONE;
+    /**
-    private State state = NEW;
+     * Constructor initializes ConnectionHandler by Setting default values for the fields and stores the given messages itself.
-
+     *
-    enum State {
+     * @param messages
-        NEW, CONFIRM_CONNECT, CONNECTED, CONFIRM_DISCONNECT, DISCONNECTED;
+     */
+    public ClientConnectionHandler(ClientMessageList messages) {
+        super();
+        this.messages = messages;
+        state = new SimpleObjectProperty<>(State.NEW);
+        serverAddress = new SimpleStringProperty(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
+        serverPort = new SimpleIntegerProperty(NetworkHandler.DEFAULT_PORT);
+        this.userName = new SimpleStringProperty(null);
     }
 
-    public ClientConnectionHandler(NetworkHandler.NetworkConnection<String> connection,
+    /**
-                                   String userName,
+     * Called to initialize the ClientConnectionHandler when trying to start a connection
-                                   ChatWindowController controller)  {
+     *
-        this.connection = connection;
+     * @param serverAddress to connect to
-        this.userName = (userName == null || userName.isBlank())? USER_NONE : userName;
+     * @param serverPort    to connect to
-        this.controller = controller;
+     * @param userName      to connect as
+     * @throws IOException if connection to Server not possible
+     */
+    public void initialize(String serverAddress, int serverPort, String userName) throws IOException {
+        state.set(NEW);
+        this.serverAddress.set(serverAddress);
+        this.serverPort.set(serverPort);
+        setConnection(NetworkHandler.openConnection(serverAddress, serverPort));
+        this.userName.set((userName == null || userName.isBlank()) ? USER_NONE : userName);
     }
 
-    public State getState() {
+    /**
+     * Observable getter Method for the stored serverAddress
+     *
+     * @return the stored serverAddress
+     */
+    public SimpleStringProperty getServerAddressProperty() {
+        return serverAddress;
+    }
+
+    /**
+     * Observable getter Method for the stored serverPort
+     *
+     * @return the stored serverPort
+     */
+    public SimpleIntegerProperty getServerPortProperty() {
+        return serverPort;
+    }
+
+    /**
+     * Observable getter Method for the stored state
+     *
+     * @return the stored state
+     */
+    public SimpleObjectProperty<State> getStateProperty() {
         return this.state;
     }
 
-    public void setState (State newState) {
+    /**
-        this.state = newState;
+     * Observable getter Method for the stored userName
-        controller.stateChanged(newState);
+     *
+     * @return the stored userName
+     */
+    public SimpleStringProperty getUserNameProperty() {
+        return userName;
     }
 
-    public void run () {
+    /**
+     * Method which sets a new State.
+     *
+     * @param newState the state that will be set
+     */
+    public void setState(State newState) {
+        state.set(newState);
+    }
+
+    /**
+     * Standard run method which will directly start the startReceiving method.
+     */
+    public void run() {
         startReceiving();
     }
 
-    public void startReceiving() {
+    /**
+     * Method that is started by the run method, starts a connection handler.
+     * Figures out if connection is available if not determines the error cause and gives an error accordingly.
+     */
+    private void startReceiving() {
         System.out.println("Starting Connection Handler");
         try {
             System.out.println("Start receiving data...");
-            while (connection.isAvailable()) {
+            while (getConnection().isAvailable()) {
-                String data = connection.receive();
+                Message data = getConnection().receive();
                 processData(data);
             }
-            System.out.println("Stopped recieving data");
+            System.out.println("Stopped receiving data");
         } catch (SocketException e) {
             System.out.println("Connection terminated locally");
             this.setState(DISCONNECTED);
@@ -69,19 +135,22 @@ public class ClientConnectionHandler implements Runnable {
             System.out.println("Connection terminated by remote");
             this.setState(DISCONNECTED);
             System.err.println("Unregistered because connection terminated" + e.getMessage());
-        } catch(IOException e) {
+        } catch (IOException e) {
             System.err.println("Communication error" + e);
-        } catch(ClassNotFoundException e) {
+        } catch (ClassNotFoundException e) {
             System.err.println("Received object of unknown type" + e.getMessage());
         }
         System.out.println("Stopped Connection Handler");
     }
 
+    /**
+     * Method which is used to stop receiving data, gets the current connection and closes it.
+     */
     public void stopReceiving() {
         System.out.println("Closing Connection Handler to Server");
         try {
             System.out.println("Stop receiving data...");
-            connection.close();
+            getConnection().close();
             System.out.println("Stopped receiving data.");
         } catch (IOException e) {
             System.err.println("Failed to close connection." + e.getMessage());
@@ -89,114 +158,129 @@ public class ClientConnectionHandler implements Runnable {
         System.out.println("Closed Connection Handler to Server");
     }
 
-    private void processData(String data) {
+    /**
-        try {
+     * Method which processes data and determines its type then uses the corresponding method to process it.
-            // parse data content
+     *
-            Scanner scanner = new Scanner(data);
+     * @param data that is received in a form of a String and then used depending on its determined cause.
-            String sender = null;
+     */
-            String reciever = null;
+    private void processData(Message data) {
-            String type = null;
-            String payload = null;
-            if (scanner.hasNextLine()) {
-                sender = scanner.nextLine();
-            } else {
-                throw new ChatProtocolException("No Sender found");
-            }
-            if (scanner.hasNextLine()) {
-                reciever = scanner.nextLine();
-            } else {
-                throw new ChatProtocolException("No Reciever found");
-            }
-            if (scanner.hasNextLine()) {
-                type = scanner.nextLine();
-            } else {
-                throw new ChatProtocolException("No Type found");
-            }
-            if (scanner.hasNextLine()) {
-                payload = scanner.nextLine();
-            }
         // dispatch operation based on type parameter
-            if (type.equals(DATA_TYPE_CONNECT)) {
+        if (data.getType() == DATA_TYPE.DATA_TYPE_CONNECT) {
             System.err.println("Illegal connect request from server");
-            } else if (type.equals(DATA_TYPE_CONFIRM)) {
+        } else if (data.getType() == DATA_TYPE.DATA_TYPE_CONFIRM) {
-                if (state == CONFIRM_CONNECT) {
+            caseConfirm(data);
-                    this.userName = reciever;
+        } else if (data.getType() == DATA_TYPE.DATA_TYPE_DISCONNECT) {
-                    controller.setUserName(userName);
+            caseDisconnect(data);
-                    controller.setServerPort(connection.getRemotePort());
+        } else if (data.getType() == DATA_TYPE.DATA_TYPE_MESSAGE) {
-                    controller.setServerAddress(connection.getRemoteHost());
+            caseMessage(data);
-                    controller.addInfo(payload);
+        } else if (data.getType() == DATA_TYPE.DATA_TYPE_ERROR) {
-                    System.out.println("CONFIRM: " + payload);
+            caseError(data);
+        } else {
+            System.out.println("Unknown data type received: " + data.getType());
+        }
+    }
+
+    private void caseConfirm(Message data) {
+        if (state.get() == CONFIRM_CONNECT) {
+            this.userName.set(data.getReceiver());
+            this.serverPort.set(getConnection().getRemotePort());
+            this.serverAddress.set(getConnection().getRemoteHost());
+            messages.addMessage(data);
+            System.out.println("CONFIRM: " + data.getText());
             this.setState(CONNECTED);
-                } else if (state == CONFIRM_DISCONNECT) {
+        } else if (state.get() == CONFIRM_DISCONNECT) {
-                    controller.addInfo(payload);
+            messages.addMessage(data);
-                    System.out.println("CONFIRM: " + payload);
+            System.out.println("CONFIRM: " + data.getText());
             this.setState(DISCONNECTED);
         } else {
-                    System.err.println("Got unexpected confirm message: " + payload);
+            System.err.println("Got unexpected confirm message: " + data.getText());
-                }
-            } else if (type.equals(DATA_TYPE_DISCONNECT)) {
-                if (state == DISCONNECTED) {
-                    System.out.println("DISCONNECT: Already in disconnected: " + payload);
-                    return;
-                }
-                controller.addInfo(payload);
-                System.out.println("DISCONNECT: " + payload);
-                this.setState(DISCONNECTED);
-            } else if (type.equals(DATA_TYPE_MESSAGE)) {
-                if (state != CONNECTED) {
-                    System.out.println("MESSAGE: Illegal state " + state + " for message: " + payload);
-                    return;
-                }
-                controller.addMessage(sender, reciever, payload);
-                System.out.println("MESSAGE: From " + sender + " to " + reciever + ": "+  payload);
-            } else if (type.equals(DATA_TYPE_ERROR)) {
-                controller.addError(payload);
-                System.out.println("ERROR: " + payload);
-            } else {
-                System.out.println("Unknown data type received: " + type);
-            }
-        } catch (ChatProtocolException e) {
-            System.err.println("Error while processing data: " + e.getMessage());
-            sendData(USER_NONE, userName, DATA_TYPE_ERROR, e.getMessage());
         }
     }
 
-    public void sendData(String sender, String receiver, String type, String payload) {
+    /**
-        if (connection.isAvailable()) {
+     * Initiates the disconnect sequence and sends the message with all its info.
-            new StringBuilder();
+     *
-            String data = new StringBuilder()
+     * @param data Data which has been transmitted
-                .append(sender+"\n")
+     */
-                .append(receiver+"\n")
+    private void caseDisconnect(Message data) {
-                .append(type+"\n")
+        if (state.get() == DISCONNECTED) {
-                .append(payload+"\n")
+            System.out.println("DISCONNECT: Already in disconnected: " + data.getText());
-                .toString();
+            return;
-            try {
-                connection.send(data);
-            } catch (SocketException e) {
-                System.err.println("Connection closed: " + e.getMessage());
-            } catch (EOFException e) {
-                System.out.println("Connection terminated by remote");
-            } catch(IOException e) {
-                System.err.println("Communication error: " + e.getMessage());
-            }
         }
+        messages.addMessage(data);
+        System.out.println("DISCONNECT: " + data.getText());
+        this.setState(DISCONNECTED);
     }
 
+    /**
+     * Initiates the procedure to send a new message and sends one as such.
+     *
+     * @param data Data which has been transmitted
+     */
+    private void caseMessage(Message data) {
+        if (state.get() != CONNECTED) {
+            System.out.println("MESSAGE: Illegal state " + state + " for message: " + data.getText());
+            return;
+        }
+        messages.addMessage(data);
+        System.out.println("MESSAGE: From " + data.getSender() + " to " + data.getReceiver() + ": " + data.getText());
+    }
+
+    /**
+     * Stores the message as an error message and displays it as such as well.
+     *
+     * @param data Data which has been transmitted
+     */
+    private void caseError(Message data) {
+        messages.addMessage(data);
+        System.out.println("ERROR: " + data.getText());
+    }
+
+    /**
+     * Send connect attempt to Server
+     *
+     * @throws ChatProtocolException Error that is thrown if the state is not set to NEW
+     */
     public void connect() throws ChatProtocolException {
-        if (state != NEW) throw new ChatProtocolException("Illegal state for connect: " + state);
+        if (state.get() != NEW) throw new ChatProtocolException("Illegal state for connect: " + state);
-        this.sendData(userName, USER_NONE, DATA_TYPE_CONNECT,null);
+        this.sendData(userName.get(), USER_NONE, getDataTypeConnect(), null);
         this.setState(CONFIRM_CONNECT);
     }
 
+    /**
+     * Send Disconnect attempt to server
+     *
+     * @throws ChatProtocolException Error tha si thrown if state is invalid
+     */
     public void disconnect() throws ChatProtocolException {
-        if (state != NEW && state != CONNECTED) throw new ChatProtocolException("Illegal state for disconnect: " + state);
+        if (state.get() != NEW && state.get() != CONNECTED)
-        this.sendData(userName, USER_NONE, DATA_TYPE_DISCONNECT,null);
+            throw new ChatProtocolException("Illegal state for disconnect: " + state);
+        this.sendData(userName.get(), USER_NONE, getDataTypeDisconnect(), null);
         this.setState(CONFIRM_DISCONNECT);
     }
 
-    public void message(String receiver, String message) throws ChatProtocolException {
+    /**
-        if (state != CONNECTED) throw new ChatProtocolException("Illegal state for message: " + state);
+     * Sends message to Server
-        this.sendData(userName, receiver, DATA_TYPE_MESSAGE,message);
+     *
-    }
+     * @param messageString The message the user wants to send
+     * @return true if message is valid else false
+     * @throws ChatProtocolException if illegal connection state
+     */
+    public boolean message(String messageString) throws ChatProtocolException {
+        if (state.get() != CONNECTED) throw new ChatProtocolException("Illegal state for message: " + state);
 
+        Matcher matcher = messagePattern.matcher(messageString);
+        if (matcher.find()) {
+            String receiver = matcher.group(1);
+            String message = matcher.group(2);
+            if (message.length() < 1) {
+                return false;
+            }
+            if (receiver == null || receiver.isBlank()) receiver = ClientConnectionHandler.USER_ALL;
+            this.sendData(userName.get(), receiver, getDataTypeMessage(), message);
+            return true;
+        } else {
+            return false;
+        }
+    }
 }

client/src/main/java/ch/zhaw/pm2/multichat/client/ClientMessageList.java

@@ -1,51 +1,68 @@
 package ch.zhaw.pm2.multichat.client;
 
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler;
+import ch.zhaw.pm2.multichat.protocol.Message;
+import javafx.beans.property.SimpleBooleanProperty;
+
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
 
+/**
+ * Class that is used to store the messages in an ArrayList
+ * And also as a Model that informs the controller via Listeners that can be initialized
+ */
 public class ClientMessageList {
-    private final List<MessageType> typeList = new ArrayList<>();
+    private List<Message> messages = new ArrayList<>();
-	private final List<String> senderList = new ArrayList<>();
+    private final SimpleBooleanProperty changed = new SimpleBooleanProperty(false);
-	private final List<String> receiverList = new ArrayList<>();
-	private final List<String> messageList = new ArrayList<>();
-	private final ChatWindowController gui;
 
-	public ClientMessageList(ChatWindowController gui) {
+    /**
-		this.gui = gui;
+     * Adds a new message to ArrayList and also informs Listener.
+     *
+     * @param message that should be added
+     */
+    public void addMessage(Message message) {
+        messages.add(message);
+        changed.set(!changed.get());
     }
 
-    public void addMessage(MessageType type, String sender, String receiver, String message) {
+    /**
-	    typeList.add(type);
+     * Applies a given filter over all messages and returns the result as a new String.
-    	senderList.add(sender);
+     * Method is also in charge of applying the correct prefix to the message according to its type.
-    	receiverList.add(receiver);
+     *
-    	messageList.add(message);
+     * @param filter is the applied filter on all the messages that are stored.
-    }
+     * @return String that matches the given filter.
-
+     */
-	public void writeFilteredMessages(String filter) {
+    public String getFilteredMessages(String filter) {
+        StringBuilder result = new StringBuilder();
         boolean showAll = filter == null || filter.isBlank();
-		gui.clearMessageArea();
+        for (Message message : messages) {
-		for(int i=0; i<senderList.size(); i++) {
+            if (showAll || message.matchesFilter(filter)) {
-		    String sender = Objects.requireNonNullElse(senderList.get(i),"");
+                switch (message.getType()) {
-		    String receiver = Objects.requireNonNullElse(receiverList.get(i),"");
+                    case DATA_TYPE_MESSAGE -> result.append(String.format("[%s -> %s] %s\n", message.getSender(), message.getReceiver(), message.getText()));
-		    String message = Objects.requireNonNull(messageList.get(i), "");
+                    case DATA_TYPE_ERROR -> result.append(String.format("[ERROR] %s\n", message.getText()));
-			if(showAll ||
+                    case DATA_TYPE_CONFIRM, DATA_TYPE_DISCONNECT, DATA_TYPE_CONNECT -> result.append(String.format("[INFO] %s\n", message.getText()));
-					sender.contains(filter) ||
+                    default -> result.append(String.format("[ERROR] %s\n", "Unexpected message type: " + message.getType()));
-					receiver.contains(filter) ||
-					message.contains(filter))
-			{
-			    switch (typeList.get(i)) {
-                    case MESSAGE: gui.writeMessage(senderList.get(i), receiverList.get(i), messageList.get(i)); break;
-                    case ERROR: gui.writeError(messageList.get(i)); break;
-                    case INFO: gui.writeInfo(messageList.get(i)); break;
-                    default: gui.writeError("Unexpected message type: " + typeList.get(i));
                 }
             }
         }
+        return result.toString();
     }
 
-    public enum MessageType {
+    /**
-        INFO, MESSAGE, ERROR;
+     * Overwrites the Arraylist of messages, clearing it, also informs all Listeners.
+     */
+    public void clear() {
+        messages = new ArrayList<>();
+        changed.set(!changed.get());
+    }
+
+    /**
+     * Getter Method to check the current value of SimpleBooleanProperty changed.
+     *
+     * @return the current value of changed
+     */
+    public SimpleBooleanProperty getChangedProperty() {
+        return changed;
     }
 
 }

client/src/main/java/ch/zhaw/pm2/multichat/client/ClientUI.java

@@ -6,17 +6,41 @@ import javafx.scene.Scene;
 import javafx.scene.layout.Pane;
 import javafx.stage.Stage;
 
+/**
+ * Class in charge of initializing and loading elements needed for the GUI.
+ * Also Launching the chat window with pre-given parameters
+ */
 public class ClientUI extends Application {
+    private final ClientMessageList clientMessageList = new ClientMessageList();
+    private final ClientConnectionHandler connectionHandler = new ClientConnectionHandler(clientMessageList);
 
+    /**
+     * Start method will only run the chatWindow method.
+     *
+     * @param primaryStage the primary stage for this application, onto which
+     *                     the application scene can be set.
+     *                     Applications may create other stages, if needed, but they will not be
+     *                     primary stages.
+     */
     @Override
     public void start(Stage primaryStage) {
         chatWindow(primaryStage);
     }
 
+    /**
+     * Method is in charge of loading the FXML file and then initializing the controllers and setting some parameters for the stage.
+     *
+     * @param primaryStage of the Application onto which the Scene is set.
+     */
     private void chatWindow(Stage primaryStage) {
         try {
             FXMLLoader loader = new FXMLLoader(getClass().getResource("ChatWindow.fxml"));
             Pane rootPane = loader.load();
+
+            ChatWindowController chatWindowController = loader.getController();
+            chatWindowController.setMessages(clientMessageList);
+            chatWindowController.setConnectionHandler(connectionHandler);
+
             // fill in scene and stage setup
             Scene scene = new Scene(rootPane);
             //scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
@@ -27,7 +51,7 @@ public class ClientUI extends Application {
             primaryStage.setTitle("Multichat Client");
             primaryStage.show();
             primaryStage.setMinWidth(primaryStage.getWidth()); //use automatically computed size as Minimum Size.
-        } catch(Exception e) {
+        } catch (Exception e) {
             System.err.println("Error starting up UI" + e.getMessage());
         }
     }

client/src/main/resources/ch/zhaw/pm2/multichat/client/ChatWindow.fxml

@@ -12,7 +12,9 @@
 <?import javafx.scene.layout.HBox?>
 <?import javafx.scene.layout.VBox?>
 
-<BorderPane fx:id="rootPane" minWidth="-Infinity" prefHeight="500.0" prefWidth="420.0" xmlns="http://javafx.com/javafx/18" xmlns:fx="http://javafx.com/fxml/1" fx:controller="ch.zhaw.pm2.multichat.client.ChatWindowController">
+<BorderPane xmlns:fx="http://javafx.com/fxml/1" fx:id="rootPane" minWidth="-Infinity" prefHeight="500.0"
+            prefWidth="420.0" xmlns="http://javafx.com/javafx/18"
+            fx:controller="ch.zhaw.pm2.multichat.client.ChatWindowController">
     <top>
         <VBox BorderPane.alignment="CENTER">
             <children>
@@ -22,7 +24,7 @@
                             <items>
                                 <MenuItem mnemonicParsing="false" text="press Enter">
                                     <graphic>
-                              <TextField fx:id="filterValue" onAction="#applyFilter" />
+                                        <TextField fx:id="filterValue" onAction="#applyFilter"/>
                                     </graphic>
                                 </MenuItem>
                             </items>
@@ -31,30 +33,35 @@
                 </MenuBar>
                 <HBox fillHeight="false" spacing="5.0">
                     <children>
-	            <TextField fx:id="userNameField" alignment="CENTER_RIGHT" maxWidth="1.7976931348623157E308" minWidth="110.0" promptText="Username" HBox.hgrow="SOMETIMES" />
+                        <TextField fx:id="userNameField" alignment="CENTER_RIGHT" maxWidth="1.7976931348623157E308"
-	            <Label alignment="CENTER" contentDisplay="CENTER" text="\@" textAlignment="CENTER" textOverrun="CLIP" HBox.hgrow="NEVER">
+                                   minWidth="110.0" promptText="Username" HBox.hgrow="SOMETIMES"/>
+                        <Label alignment="CENTER" contentDisplay="CENTER" text="\@" textAlignment="CENTER"
+                               textOverrun="CLIP" HBox.hgrow="NEVER">
                             <HBox.margin>
-	                  <Insets bottom="5.0" top="5.0" />
+                                <Insets bottom="5.0" top="5.0"/>
                             </HBox.margin>
                         </Label>
-	            <TextField fx:id="serverAddressField" alignment="CENTER_RIGHT" minWidth="110.0" promptText="Host" HBox.hgrow="SOMETIMES" />
+                        <TextField fx:id="serverAddressField" alignment="CENTER_RIGHT" minWidth="110.0"
+                                   promptText="Host" HBox.hgrow="SOMETIMES"/>
                         <Label text=":" HBox.hgrow="NEVER">
                             <HBox.margin>
-	                  <Insets bottom="5.0" top="5.0" />
+                                <Insets bottom="5.0" top="5.0"/>
                             </HBox.margin>
                         </Label>
-	            <TextField fx:id="serverPortField" minWidth="-Infinity" prefWidth="60.0" promptText="Port" HBox.hgrow="NEVER" />
+                        <TextField fx:id="serverPortField" minWidth="-Infinity" prefWidth="60.0" promptText="Port"
-	            <Button fx:id="connectButton" maxWidth="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#toggleConnection" prefWidth="80.0" text="Connect" HBox.hgrow="NEVER">
+                                   HBox.hgrow="NEVER"/>
+                        <Button fx:id="connectButton" maxWidth="-Infinity" minWidth="-Infinity" mnemonicParsing="false"
+                                onAction="#toggleConnection" prefWidth="80.0" text="Connect" HBox.hgrow="NEVER">
                             <HBox.margin>
-	                  <Insets left="5.0" />
+                                <Insets left="5.0"/>
                             </HBox.margin>
                         </Button>
                     </children>
                     <BorderPane.margin>
-	            <Insets />
+                        <Insets/>
                     </BorderPane.margin>
                     <padding>
-	            <Insets bottom="5.0" left="5.0" right="5.0" top="5.0" />
+                        <Insets bottom="5.0" left="5.0" right="5.0" top="5.0"/>
                     </padding>
                 </HBox>
             </children>
@@ -63,22 +70,23 @@
     <bottom>
         <HBox spacing="5.0">
             <children>
-            <TextField fx:id="messageField" onAction="#message" HBox.hgrow="ALWAYS" />
+                <TextField fx:id="messageField" onAction="#message" HBox.hgrow="ALWAYS"/>
-            <Button fx:id="sendButton" alignment="CENTER" maxWidth="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#message" prefWidth="50.0" text="Send" textAlignment="CENTER">
+                <Button fx:id="sendButton" alignment="CENTER" maxWidth="-Infinity" minWidth="-Infinity"
+                        mnemonicParsing="false" onAction="#message" prefWidth="50.0" text="Send" textAlignment="CENTER">
                     <HBox.margin>
-                  <Insets left="5.0" />
+                        <Insets left="5.0"/>
                     </HBox.margin>
                 </Button>
             </children>
             <padding>
-            <Insets bottom="5.0" left="5.0" right="5.0" top="5.0" />
+                <Insets bottom="5.0" left="5.0" right="5.0" top="5.0"/>
             </padding>
         </HBox>
     </bottom>
     <center>
         <TextArea fx:id="messageArea" editable="false" wrapText="true">
             <BorderPane.margin>
-            <Insets left="5.0" right="5.0" />
+                <Insets left="5.0" right="5.0"/>
             </BorderPane.margin>
         </TextArea>
     </center>

protocol/src/main/java/ch/zhaw/pm2/multichat/protocol/ConnectionHandler.java

@@ -0,0 +1,101 @@
+package ch.zhaw.pm2.multichat.protocol;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.net.SocketException;
+
+/**
+ * This abstract class is the superclass for ClientConnectionHandler and ServerConnectionHandler
+ * It offers the DATA_TYPE for message and a {@link State} enum for all valid connection states.
+ * Shared methods are implemented in this class as well {@link ConnectionHandler#sendData(String, String, DATA_TYPE, String)}
+ */
+public abstract class ConnectionHandler {
+    private NetworkHandler.NetworkConnection<String> connection;
+
+    public static final String USER_NONE = "";
+    public static final String USER_ALL = "*";
+
+    // State of the connection
+    public enum State {
+        NEW, CONFIRM_CONNECT, CONNECTED, CONFIRM_DISCONNECT, DISCONNECTED, ERROR;
+    }
+
+    // DATA_TYPE of the messages
+    public enum DATA_TYPE {
+        DATA_TYPE_CONNECT, DATA_TYPE_CONFIRM, DATA_TYPE_DISCONNECT, DATA_TYPE_MESSAGE, DATA_TYPE_ERROR
+    }
+
+    /**
+     * @return {@link DATA_TYPE}
+     */
+    public static DATA_TYPE getDataTypeConnect() {
+        return DATA_TYPE.DATA_TYPE_CONNECT;
+    }
+
+    /**
+     * @return {@link DATA_TYPE}
+     */
+    public static DATA_TYPE getDataTypeConfirm() {
+        return DATA_TYPE.DATA_TYPE_CONFIRM;
+    }
+
+    /**
+     * @return {@link DATA_TYPE}
+     */
+    public static DATA_TYPE getDataTypeDisconnect() {
+        return DATA_TYPE.DATA_TYPE_DISCONNECT;
+    }
+
+    /**
+     * @return {@link DATA_TYPE}
+     */
+    public static DATA_TYPE getDataTypeMessage() {
+        return DATA_TYPE.DATA_TYPE_MESSAGE;
+    }
+
+    /**
+     * @return {@link DATA_TYPE}
+     */
+    public static DATA_TYPE getDataTypeError() {
+        return DATA_TYPE.DATA_TYPE_ERROR;
+    }
+
+    /**
+     * @return {@link NetworkHandler.NetworkConnection}
+     */
+    public NetworkHandler.NetworkConnection<String> getConnection() {
+        return connection;
+    }
+
+    /**
+     * This method sets the NetworkConnection used for the server <-> client connection
+     *
+     * @param connection NetworkConnection used for the server <-> client connection
+     */
+    protected void setConnection(NetworkHandler.NetworkConnection<String> connection) {
+        this.connection = connection;
+    }
+
+
+    /**
+     * This method gets called to send data via the socket defined in the {@link NetworkHandler.NetworkConnection}
+     *
+     * @param sender   of the data
+     * @param receiver of the data
+     * @param type     of the data
+     * @param payload  of the data
+     */
+    protected void sendData(String sender, String receiver, DATA_TYPE type, String payload) {
+        if (connection.isAvailable()) {
+            try {
+                connection.send(new Message(type, sender, receiver, payload));
+            } catch (SocketException e) {
+                System.err.println("Connection closed: " + e.getMessage());
+            } catch (EOFException e) {
+                System.out.println("Connection terminated by remote");
+            } catch (IOException e) {
+                System.err.println("Communication error: " + e.getMessage());
+            }
+        }
+    }
+}

protocol/src/main/java/ch/zhaw/pm2/multichat/protocol/Message.java

@@ -0,0 +1,69 @@
+package ch.zhaw.pm2.multichat.protocol;
+
+import java.io.Serializable;
+
+/**
+ * A Message object represents one Message of a client. Can be stored in ClientMessageList.
+ */
+public class Message implements Serializable {
+    private final ConnectionHandler.DATA_TYPE type;
+    private final String sender;
+    private final String receiver;
+    private final String text;
+
+    /**
+     * Constructor of Message. Needs all Information about a Message to save them.
+     *
+     * @param type     Message (if it's a message typed by a user), Error or Information (if it is generated automatically, in this case sender and receiver will be null)
+     * @param sender   The User who has sent the message.
+     * @param receiver The User who should receive the message.
+     * @param text     The Text of the message.
+     */
+    public Message(ConnectionHandler.DATA_TYPE type, String sender, String receiver, String text) {
+        this.type = type;
+        this.sender = sender;
+        this.receiver = receiver;
+        this.text = text;
+    }
+
+    /**
+     * Checks if the Filter String is contained in one of the data fields sender, receiver or text
+     *
+     * @param filter The Filter String
+     * @return true if it is the Filter String is contained in a data field.
+     */
+    public boolean matchesFilter(String filter) {
+        return (sender != null && sender.contains(filter)) ||
+                (receiver != null && receiver.contains(filter)) ||
+                (text != null && text.contains(filter));
+    }
+
+    /**
+     * @return The type of the message.
+     */
+    public ConnectionHandler.DATA_TYPE getType() {
+        return type;
+    }
+
+    /**
+     * @return The User who has sent the Message.
+     */
+    public String getSender() {
+        return sender;
+    }
+
+    /**
+     * @return The Receiver who receives the Message.
+     */
+    public String getReceiver() {
+        return receiver;
+    }
+
+    /**
+     * @return The Text of the Message.
+     */
+    public String getText() {
+        return text;
+    }
+
+}

protocol/src/main/java/ch/zhaw/pm2/multichat/protocol/NetworkHandler.java

@@ -38,7 +38,7 @@ import java.util.Objects;
  *             on the client side, usually the result is displayed to the user). After processing is finished the
  *             process calls {@link NetworkConnection#receive()} again to wait for the next request.
  *             </li>
- *             <li>sending data: call {@link NetworkConnection#send(Serializable data)}, which sends the given data
+ *             <li>sending data: call {@link NetworkConnection#send(Message)}, which sends the given data
  *             object to the remote side. The method returns as soon the object has been transmitted.
  *             <b>Important: {@link NetworkConnection} is not thread safe</b>, therefore make sure that only one thread
  *             at a time is sending data.</li>
@@ -270,7 +270,7 @@ public class NetworkHandler {
      *         on the client side, usually the result is displayed to the user). After processing is finished the
      *         process calls {@link NetworkConnection#receive()} again to wait for the next request.
      *     </li>
-     *     <li>sending data: call {@link NetworkConnection#send(Serializable data)}, which sends the given data
+     *     <li>sending data: call {@link NetworkConnection#send(Message)}, which sends the given data
      *         object to the remote side. The method returns as soon the object has been transmitted.
      *         <b>Important: {@link NetworkConnection} is not thread safe</b>, therefore make sure that only one thread
      *         at a time is sending data.
@@ -305,7 +305,7 @@ public class NetworkHandler {
          * @param data  data object of type T to be submitted through the connection.
          * @throws IOException if an error occurs (e.g. connection interrupted while sending, ...)
          */
-        public synchronized void send(T data) throws IOException {
+        public synchronized void send(Message data) throws IOException {
             ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream());
             outputStream.writeObject(data);
         }
@@ -320,9 +320,9 @@ public class NetworkHandler {
          * @throws IOException if an error occours. (e.g. terminated locally/remotely) see above.
          * @throws ClassNotFoundException if the data object received does not match any class in the local classpath
          */
-        public T receive() throws IOException, ClassNotFoundException {
+        public Message receive() throws IOException, ClassNotFoundException {
             ObjectInputStream inputStream = new ObjectInputStream(this.socket.getInputStream());
-            return (T) inputStream.readObject();
+            return (Message) inputStream.readObject();
         }
 
         /**

server/src/main/java/ch/zhaw/pm2/multichat/server/Server.java

@@ -8,14 +8,38 @@ import java.util.HashMap;
 import java.util.Map;
 
 
+/**
+ * This Class represents a Server. The user can start the programm with the port number as a argument.
+ * If no argument has been set the {@link NetworkHandler#DEFAULT_PORT} is used as port number.
+ * After initialising the server:
+ * 1. Starts a Socketserver using the logic given in {@link NetworkHandler.NetworkServer#createServer()}
+ * 2. The server starts to listen for incoming connection using the Logic given in {@link NetworkHandler.NetworkServer#waitForConnection()}
+ * 3. New connections will be attached to a Connection handler: {@link ServerConnectionHandler} and placed in a Map containing all active connections {@link Server#connections}
+ */
 public class Server {
 
     // Server connection
-    private NetworkHandler.NetworkServer<String> networkServer;
+    private final NetworkHandler.NetworkServer<String> networkServer;
 
     // Connection registry
-    private Map<String,ServerConnectionHandler> connections = new HashMap<>();
+    private final Map<String, ServerConnectionHandler> connections = new HashMap<>();
 
+    /**
+     * The Constructor to create a new instance.
+     *
+     * @param serverPort to listen for incoming connections.
+     * @throws IOException thrown if an I/O error occurs when opening the socket.
+     */
+    public Server(int serverPort) throws IOException {
+        // Open server connection
+        System.out.println("Create server connection");
+        networkServer = NetworkHandler.createServer(serverPort);
+        System.out.println("Listening on " + networkServer.getHostAddress() + ":" + networkServer.getHostPort());
+    }
+
+    /**
+     * @param args
+     */
     public static void main(String[] args) {
         // Parse arguments for server port.
         try {
@@ -54,36 +78,30 @@ public class Server {
         }
     }
 
-    public Server(int serverPort) throws IOException {
+    /**
-        // Open server connection
+     * With this methode the instance waits for incoming connections. If a client tries to connect to the server.
-        System.out.println("Create server connection");
+     * The connection will be registered in the connection registry if successful.
-        networkServer = NetworkHandler.createServer(serverPort);
+     */
-        System.out.println("Listening on " + networkServer.getHostAddress() + ":" + networkServer.getHostPort());
-    }
-
     private void start() {
         System.out.println("Server started.");
         try {
-            while (true) {
+            while (networkServer.isAvailable()) {
                 NetworkHandler.NetworkConnection<String> connection = networkServer.waitForConnection();
                 ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections);
                 new Thread(connectionHandler).start();
-                 System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
-                     connectionHandler.getUserName(),
-                     connection.getRemoteHost(),
-                     connection.getRemotePort()
-                 ));
             }
-        } catch(SocketException e) {
+        } catch (SocketException e) {
             System.out.println("Server connection terminated");
-        }
+        } catch (IOException e) {
-        catch (IOException e) {
             System.err.println("Communication error " + e);
         }
         // close server
         System.out.println("Server Stopped.");
     }
 
+    /**
+     * This method will stop the serversocket.
+     */
     public void terminate() {
         try {
             System.out.println("Close server port.");

server/src/main/java/ch/zhaw/pm2/multichat/server/ServerConnectionHandler.java

@@ -1,68 +1,92 @@
 package ch.zhaw.pm2.multichat.server;
 
 import ch.zhaw.pm2.multichat.protocol.ChatProtocolException;
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler;
+
+import static ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State.*;
+
+import ch.zhaw.pm2.multichat.protocol.Message;
 import ch.zhaw.pm2.multichat.protocol.NetworkHandler;
 
 import java.io.EOFException;
 import java.io.IOException;
 import java.net.SocketException;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Scanner;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
 
-import static ch.zhaw.pm2.multichat.server.ServerConnectionHandler.State.*;
 
-public class ServerConnectionHandler implements Runnable{
+/**
+ * This class represents the connection between the server and a client and offers the serverside logic.
+ * The ServerConnectionHandler receives data send from the client as well as sends data to the client.
+ * <p>
+ * The ServeConnectionHandler offers following functionality:
+ * <p>
+ * Evaluating connection attempts from a client by:
+ * 1. Checks if Username is valid (Not used)
+ * 2. Saves Username in {@link ServerConnectionHandler#userName}
+ * 3. Saves the connection in the {@link ServerConnectionHandler#connectionRegistry}
+ * <p>
+ * Processes disconnections from a client by:
+ * 1. Removing the connection from the {@link ServerConnectionHandler#connectionRegistry}
+ * 2. Terminates the socket by calling {@link NetworkHandler.NetworkConnection#close()}
+ * <p>
+ * Process Messages send from a client by:
+ * 1. Evaluating the receiver by differentiating between broadcast or unicast.
+ * 2. Sending the message accordingly.
+ * <p>
+ * To use this class, start a new instance and start it in a thread.
+ * To constructor needs following parameter:
+ * 1. {@link ch.zhaw.pm2.multichat.protocol.NetworkHandler.NetworkConnection} representing the socket connection between server and client
+ * 2. {@link Map<String,ServerConnectionHandler>} registry to check for all active connections
+ * 3. {@link ReentrantLock @link Condition} to lock server thread to evaluate connection.
+ */
+public class ServerConnectionHandler extends ConnectionHandler implements Runnable {
     private static final AtomicInteger connectionCounter = new AtomicInteger(0);
     private final int connectionId = connectionCounter.incrementAndGet();
-    private final NetworkHandler.NetworkConnection<String> connection;
+    private final Map<String, ServerConnectionHandler> connectionRegistry;
-    private final Map<String,ServerConnectionHandler> connectionRegistry;
 
-    // Data types used for the Chat Protocol
+    private String userName = "Anonymous-" + connectionId;
-    private static final String DATA_TYPE_CONNECT = "CONNECT";
-    private static final String DATA_TYPE_CONFIRM = "CONFIRM";
-    private static final String DATA_TYPE_DISCONNECT = "DISCONNECT";
-    private static final String DATA_TYPE_MESSAGE = "MESSAGE";
-    private static final String DATA_TYPE_ERROR = "ERROR";
-
-    private static final String USER_NONE = "";
-    private static final String USER_ALL = "*";
-
-    private String userName = "Anonymous-"+connectionId;
     private State state = NEW;
 
+    /**
+     * Called when runnable gets started in a thread.
+     */
     @Override
     public void run() {
         startReceiving();
     }
 
-    enum State {
+    /**
-        NEW, CONNECTED, DISCONNECTED;
+     * Constructor to initialize the connection
-    }
+     *
-
+     * @param connection representing the socket connection between server and client
+     * @param registry   map containing all active connections between server and clients
+     */
     public ServerConnectionHandler(NetworkHandler.NetworkConnection<String> connection,
-                                   Map<String,ServerConnectionHandler> registry) {
+                                   Map<String, ServerConnectionHandler> registry) {
+        super();
+        setConnection(connection);
         Objects.requireNonNull(connection, "Connection must not be null");
         Objects.requireNonNull(registry, "Registry must not be null");
-        this.connection = connection;
         this.connectionRegistry = registry;
     }
 
-    public String getUserName() {
+    /**
-        return this.userName;
+     * These methods runs in a while-loop as long as the socket between server and client is available
-    }
+     * and the connection State is not ERROR.
-
+     */
-    public void startReceiving() {
+    private void startReceiving() {
-        System.out.println("Starting Connection Handler for " + userName);
+        System.out.println("Starting Connection Handler for new User");
         try {
             System.out.println("Start receiving data...");
-            while (connection.isAvailable()) {
+            while (getConnection().isAvailable() && !(state == ERROR)) {
-                String data = connection.receive();
+                Message data = getConnection().receive();
                 processData(data);
             }
-            System.out.println("Stopped recieving data");
+            System.out.println("Stopped receiving data");
         } catch (SocketException e) {
             System.out.println("Connection terminated locally");
             connectionRegistry.remove(userName);
@@ -71,117 +95,138 @@ public class ServerConnectionHandler implements Runnable{
             System.out.println("Connection terminated by remote");
             connectionRegistry.remove(userName);
             System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
-        } catch(IOException e) {
+        } catch (IOException e) {
             System.err.println("Communication error: " + e);
-        } catch(ClassNotFoundException e) {
+        } catch (ClassNotFoundException e) {
             System.err.println("Received object of unknown type: " + e.getMessage());
         }
+        if (state == ERROR) {
+            System.out.println("Stopping Connection Handler for Rejected Client");
+        } else {
             System.out.println("Stopping Connection Handler for " + userName);
         }
 
-    public void stopReceiving() {
+    }
+
+    /**
+     * This method will call {@link NetworkHandler.NetworkConnection#close()} to close the Socket.
+     */
+    private void stopReceiving() {
         System.out.println("Closing Connection Handler for " + userName);
         try {
             System.out.println("Stop receiving data...");
-            connection.close();
+            getConnection().close();
             System.out.println("Stopped receiving data.");
         } catch (IOException e) {
-            System.err.println("Failed to close connection." + e);
+            System.err.println("Failed to close connection." + e.getMessage());
         }
         System.out.println("Closed Connection Handler for " + userName);
     }
 
-    private void processData(String data)  {
+    /**
+     * This method gets called when socket receives data. The method checks for the data type and reacts accordingly
+     * If data type:
+     * 1. Connect => checks if username is valid. if valid sends response to client with confirmation.
+     * If username not valid quits connection by changing status to ERROR.
+     * 2. Confirm => Server should not receive this kind of message. STDOUT informs about it.
+     * 3. Disconnect => Disconnects connection by removing connection from registry and calling method to terminate socket.
+     * 4. Message => Checks if broadcast or unicast. Sends data accordingly
+     * 5. Error => STDERR message
+     *
+     * @param data received by the server
+     */
+    private void processData(Message data) {
         try {
-            // parse data content
+            // dispatch operation based on type parameter
-            Scanner scanner = new Scanner(data);
+            if (data.getType() == DATA_TYPE.DATA_TYPE_CONNECT) {
-            String sender = null;
+                caseConnect(data);
-            String reciever = null;
+            } else if (data.getType() == DATA_TYPE.DATA_TYPE_CONFIRM) {
-            String type = null;
+                System.out.println("Not expecting to receive a CONFIRM request from client");
-            String payload = null;
+            } else if (data.getType() == DATA_TYPE.DATA_TYPE_DISCONNECT) {
-            if (scanner.hasNextLine()) {
+                caseDisconnect();
-                sender = scanner.nextLine();
+            } else if (data.getType() == DATA_TYPE.DATA_TYPE_MESSAGE) {
+                caseMessage(data);
+            } else if (data.getType() == DATA_TYPE.DATA_TYPE_ERROR) {
+                System.err.println("Received error from client (" + data.getSender() + "): " + data.getText());
             } else {
-                throw new ChatProtocolException("No Sender found");
+                System.err.println("Unknown data type received: " + data.getType());
+
             }
-            if (scanner.hasNextLine()) {
+        } catch (ChatProtocolException e) {
-                reciever = scanner.nextLine();
+            System.out.println("Error while processing data " + e.getMessage());
-            } else {
+            sendData(USER_NONE, userName, getDataTypeError(), e.getMessage());
-                throw new ChatProtocolException("No Reciever found");
         }
-            if (scanner.hasNextLine()) {
-                type = scanner.nextLine();
-            } else {
-                throw new ChatProtocolException("No Type found");
-            }
-            if (scanner.hasNextLine()) {
-                payload = scanner.nextLine();
     }
 
-            // dispatch operation based on type parameter
+    /**
-            if (type.equals(DATA_TYPE_CONNECT)) {
+     * This method is called by method {@link ServerConnectionHandler#processData(Message)}
+     * Checks if username is valid. if valid sends response to client with confirmation.
+     *
+     * @param data sent
+     * @throws ChatProtocolException if username not valid
+     */
+    private void caseConnect(Message data) throws ChatProtocolException {
         if (this.state != NEW) throw new ChatProtocolException("Illegal state for connect request: " + state);
-                if (sender == null || sender.isBlank()) sender = this.userName;
+        //if username not valid
-                if (connectionRegistry.containsKey(sender))
+        if (connectionRegistry.containsKey(data.getSender())) {
-                    throw new ChatProtocolException("User name already taken: " + sender);
+            state = ERROR;
-                this.userName = sender;
+            System.out.println(String.format("Connecting failed for new Client with IP:Port <%s:%d>.\nReason: Name already taken.",
+                    getConnection().getRemoteHost(),
+                    getConnection().getRemotePort()));
+            throw new ChatProtocolException("User name already taken: " + data.getSender());
+        }
+        //if username valid
+        if (!data.getSender().isBlank()) {
+            this.userName = data.getSender();
+        }
         connectionRegistry.put(userName, this);
-                sendData(USER_NONE, userName, DATA_TYPE_CONFIRM, "Registration successfull for " + userName);
+        sendData(USER_NONE, userName, getDataTypeConfirm(), "Registration successful for " + userName);
         this.state = CONNECTED;
-            } else if (type.equals(DATA_TYPE_CONFIRM)) {
+        System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
-                System.out.println("Not expecting to receive a CONFIRM request from client");
+                userName,
-            } else if (type.equals(DATA_TYPE_DISCONNECT)) {
+                getConnection().getRemoteHost(),
+                getConnection().getRemotePort()));
+    }
+
+    /**
+     * This method is called by method {@link ServerConnectionHandler#processData(Message)}
+     * Disconnects connection by removing connection from registry and calling method {@link ServerConnectionHandler#stopReceiving()} to terminate socket.
+     *
+     * @throws ChatProtocolException if state already DISCONNECTED.
+     */
+    private void caseDisconnect() throws ChatProtocolException {
         if (state == DISCONNECTED)
             throw new ChatProtocolException("Illegal state for disconnect request: " + state);
         if (state == CONNECTED) {
             connectionRegistry.remove(this.userName);
         }
-                sendData(USER_NONE, userName, DATA_TYPE_CONFIRM, "Confirm disconnect of " + userName);
+        sendData(USER_NONE, userName, getDataTypeConfirm(), "Confirm disconnect of " + userName);
         this.state = DISCONNECTED;
         this.stopReceiving();
-            } else if (type.equals(DATA_TYPE_MESSAGE)) {
+    }
+
+    /**
+     * This method is called by method {@link ServerConnectionHandler#processData(Message)}
+     * Checks if broadcast or unicast. Sends data accordingly
+     *
+     * @param data to transmit
+     * @throws ChatProtocolException if state not equal to CONNECT
+     */
+    private void caseMessage(Message data) throws ChatProtocolException {
         if (state != CONNECTED) throw new ChatProtocolException("Illegal state for message request: " + state);
-                if (USER_ALL.equals(reciever)) {
+        if (USER_ALL.equals(data.getReceiver())) {
             for (ServerConnectionHandler handler : connectionRegistry.values()) {
-                        handler.sendData(sender, reciever, type, payload);
+                handler.sendData(data.getSender(), data.getReceiver(), data.getType(), data.getText());
             }
         } else {
-                    ServerConnectionHandler handler = connectionRegistry.get(reciever);
+            ServerConnectionHandler handler = connectionRegistry.get(data.getReceiver());
             if (handler != null) {
-                        handler.sendData(sender, reciever, type, payload);
+                handler.sendData(data.getSender(), data.getReceiver(), data.getType(), data.getText());
+                if (!data.getReceiver().equals(data.getSender())) {
+                    sendData(data.getSender(), data.getReceiver(), data.getType(), data.getText()); //send message to sender if it's a direct message and sender is not receiver.
+                }
             } else {
-                        this.sendData(USER_NONE, userName, DATA_TYPE_ERROR, "Unknown User: " + reciever);
+                this.sendData(USER_NONE, userName, getDataTypeError(), "Unknown User: " + data.getReceiver());
-                    }
-                }
-            } else if (type.equals(DATA_TYPE_ERROR)) {
-                System.err.println("Received error from client (" + sender + "): " + payload);
-            } else {
-                System.err.println("Unknown data type received: " + type);
-
-            }
-        } catch(ChatProtocolException e) {
-            System.out.println("Error while processing data" + e.getMessage());
-            sendData(USER_NONE, userName, DATA_TYPE_ERROR, e.getMessage());
-        }
-    }
-
-    public void sendData(String sender, String receiver, String type, String payload) {
-        if (connection.isAvailable()) {
-            new StringBuilder();
-            String data = new StringBuilder()
-                .append(sender+"\n")
-                .append(receiver+"\n")
-                .append(type+"\n")
-                .append(payload+"\n")
-                .toString();
-            try {
-                connection.send(data);
-            } catch (SocketException e) {
-                System.out.println("Connection closed: " + e.getMessage());
-            } catch (EOFException e) {
-                System.out.println("Connection terminated by remote");
-            } catch(IOException e) {
-                System.out.println("Communication error: " + e.getMessage());
             }
         }
     }