Solved #48 make it impossible to send messages if not connected in ChatWindow.

Java doc and formatting

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

@@ -1,8 +1,7 @@
 package ch.zhaw.pm2.multichat.client;
 
-import ch.zhaw.pm2.multichat.client.ClientConnectionHandler.State;
+import ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State;
 import ch.zhaw.pm2.multichat.protocol.ChatProtocolException;
-import ch.zhaw.pm2.multichat.protocol.NetworkHandler;
 import javafx.application.Platform;
 import javafx.beans.value.ChangeListener;
 import javafx.beans.value.ObservableValue;
@@ -15,45 +14,74 @@ 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 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() {
-        serverAddressField.setText(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
-        serverPortField.setText(String.valueOf(NetworkHandler.DEFAULT_PORT));
-    }
+    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 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()));
+        refreshConnectionState(connectionHandler.getStateProperty().get());
+    }
+
+    /**
+     * Method which closes the Application via use of the disconnect Method.
+     */
     private void applicationClose() {
         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.getStateProperty().get() != CONNECTED) {
             connect();
         } else {
@@ -61,16 +89,22 @@ public class ChatWindowController {
         }
     }
 
+    /**
+     * Initiates a connection by starting Connection Handler and telling, the Handler to start a connection.
+     */
     private void connect() {
         try {
             messages.clear(); // clear message list
             startConnectionHandler();
             connectionHandler.connect();
-        } catch(ChatProtocolException | IOException e) {
-            addError(e.getMessage());
+        } catch (ChatProtocolException | IOException e) {
+            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) {
             addError("No connection handler");
@@ -83,6 +117,9 @@ public class ChatWindowController {
         }
     }
 
+    /**
+     * Method which is used when the send button is pressed and handing over a message to the Connection Handler
+     */
     @FXML
     private void message() {
         String messageString = messageField.getText().strip();
@@ -99,49 +136,66 @@ public class ChatWindowController {
         }
     }
 
+    /**
+     * 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( ) {
-    	this.redrawMessageList();
+    private void applyFilter() {
+        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();
-        String serverAddress = serverAddressField.getText();
-        int serverPort = Integer.parseInt(serverPortField.getText());
-        connectionHandler = new ClientConnectionHandler(
-            NetworkHandler.openConnection(serverAddress, serverPort), userName,
-            messages);
-        new Thread(connectionHandler).start();
+        if (!userName.contains(" ")) {
+            String serverAddress = serverAddressField.getText();
+            int serverPort = Integer.parseInt(serverPortField.getText());
+            connectionHandler.initialize(serverAddress, serverPort, userName);
+            new Thread(connectionHandler).start();
 
-        //register Listener
-        startListener();
-
-        // register window close handler
-        rootPane.getScene().getWindow().addEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
-    }
-
-    private void terminateConnectionHandler() {
-        // unregister window close handler
-        rootPane.getScene().getWindow().removeEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
-        if (connectionHandler != null) {
-            connectionHandler.stopReceiving();
-            connectionHandler = null;
+            rootPane.getScene().getWindow().addEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
+        } else {
+            addError("It is not allowed to have spaces in username!");
         }
     }
 
-    public void stateChanged(State newState) {
+    /**
+     * 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 refreshConnectionState(State newState) {
         // update UI (need to be run in UI thread: see Platform.runLater())
         Platform.runLater(new Runnable() {
             @Override
             public void run() {
-                connectButton.setText((newState == CONNECTED || newState == CONFIRM_DISCONNECT) ? "Disconnect" : "Connect");
+                if(newState == CONNECTED || newState == CONFIRM_DISCONNECT){
+                    connectButton.setText("Disconnect");
+                    messageField.setDisable(false);
+                    sendButton.setDisable(false);
+                } else {
+                    connectButton.setText("Connect");
+                    messageField.setDisable(true);
+                    sendButton.setDisable(true);
+                }
             }
         });
         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 +205,11 @@ 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 +219,11 @@ 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
@@ -169,27 +233,37 @@ public class ChatWindowController {
         });
     }
 
+    /**
+     * Method which adds an incoming String as an Error Message.
+     *
+     * @param message String to be added as Error
+     */
     public void addError(String message) {
         messages.addMessage(new Message(Message.MessageType.ERROR, null, null, message));
     }
 
-    private void redrawMessageList() {
-        this.messageArea.clear();
-        Platform.runLater(() -> this.messageArea.setText(messages.getFilteredMessages(filterValue.getText().strip())));
-    }
-
+    /**
+     * Nested Class in charge of Closing the window
+     */
     class WindowCloseHandler implements EventHandler<WindowEvent> {
+
+        /**
+         *
+         * @param event the event which occurred when Windows is closed
+         */
         public void handle(WindowEvent event) {
             applicationClose();
         }
-
     }
 
-    public void startListener() {
+    /**
+     * 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);
+                refreshConnectionState(newValue);
             }
         });
 
@@ -215,11 +289,14 @@ public class ChatWindowController {
         });
     }
 
+    /**
+     * 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) {
-                redrawMessageList();
+                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

@@ -1,6 +1,7 @@
 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.NetworkHandler;
 import javafx.beans.property.SimpleIntegerProperty;
 import javafx.beans.property.SimpleObjectProperty;
@@ -13,72 +14,118 @@ 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
+ * 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 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 final Pattern messagePattern = Pattern.compile("^(?:@(\\S*))?\\s*(.*)$");
 
-    public static final String USER_NONE = "";
-    public static final String USER_ALL = "*";
+    private final SimpleStringProperty userName;
+    private final SimpleObjectProperty<State> state;
+    private final ClientMessageList messages;
+    private final SimpleStringProperty serverAddress;
+    private final SimpleIntegerProperty serverPort;
 
-    private final Pattern messagePattern = Pattern.compile( "^(?:@(\\w*))?\\s*(.*)$" );
-
-    private SimpleStringProperty userName;
-    private SimpleObjectProperty<State> state;
-    private ClientMessageList messages;
-    private SimpleStringProperty serverAddress;
-    private SimpleIntegerProperty serverPort;
-
-    enum State {
-        NEW, CONFIRM_CONNECT, CONNECTED, CONFIRM_DISCONNECT, DISCONNECTED;
-    }
-
-    public ClientConnectionHandler(NetworkHandler.NetworkConnection<String> connection,
-                                   String userName,
-                                   ClientMessageList messages)  {
-        this.connection = connection;
-        this.userName = new SimpleStringProperty((userName == null || userName.isBlank())? USER_NONE : userName);
+    /**
+     * Constructor initializes ConnectionHandler by Setting default values for the fields and stores the given messages itself.
+     *
+     * @param messages
+     */
+    public ClientConnectionHandler(ClientMessageList messages) {
+        super();
         this.messages = messages;
-        state = new SimpleObjectProperty<>(NEW);
-        serverAddress = new SimpleStringProperty();
-        serverPort = new SimpleIntegerProperty();
+        state = new SimpleObjectProperty<>(State.NEW);
+        serverAddress = new SimpleStringProperty(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
+        serverPort = new SimpleIntegerProperty(NetworkHandler.DEFAULT_PORT);
+        this.userName = new SimpleStringProperty(null);
     }
 
-    public SimpleStringProperty getServerAddressProperty() { return serverAddress; }
+    /**
+     * Called to initialize the ClientConnectionHandler when trying to start a connection
+     *
+     * @param serverAddress to connect to
+     * @param serverPort to connect to
+     * @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 SimpleIntegerProperty getServerPortProperty() { return serverPort; }
+    /**
+     * 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 SimpleStringProperty getUserNameProperty() { return userName; }
-
-    public void setState (State newState) {
-        state.set(newState);
-
+    /**
+     * Observable getter Method for the stored userName
+     *
+     * @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()) {
-                String data = connection.receive();
+            while (getConnection().isAvailable()) {
+                String 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);
@@ -87,19 +134,22 @@ 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());
@@ -107,110 +157,132 @@ public class ClientConnectionHandler implements Runnable {
         System.out.println("Closed Connection Handler to Server");
     }
 
+    /**
+     * Method which processes data and determines its type then uses the corresponding method to process it.
+     *
+     * @param data that is received in a form of a String and then used depending on its determined cause.
+     */
     private void processData(String data) {
         try {
-            // parse data content
             Scanner scanner = new Scanner(data);
-            String sender = null;
-            String reciever = null;
-            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();
-            }
+            StringBuilder sender = new StringBuilder();
+            StringBuilder receiver = new StringBuilder();
+            StringBuilder type = new StringBuilder();
+            StringBuilder payload = new StringBuilder();
+            super.processData(scanner, sender, receiver, type, payload);
+
             // dispatch operation based on type parameter
-            if (type.equals(DATA_TYPE_CONNECT)) {
+            if (type.toString().equals(getDataTypeConnect())) {
                 System.err.println("Illegal connect request from server");
-            } else if (type.equals(DATA_TYPE_CONFIRM)) {
-                if (state.get() == CONFIRM_CONNECT) {
-                    this.userName.set(reciever);
-                    this.serverPort.set(connection.getRemotePort());
-                    this.serverAddress.set(connection.getRemoteHost());
-                    messages.addMessage(new Message(Message.MessageType.INFO,sender,reciever,payload));
-                    System.out.println("CONFIRM: " + payload);
-                    this.setState(CONNECTED);
-                } else if (state.get() == CONFIRM_DISCONNECT) {
-                    messages.addMessage(new Message(Message.MessageType.INFO,sender,reciever,payload));
-                    System.out.println("CONFIRM: " + payload);
-                    this.setState(DISCONNECTED);
-                } else {
-                    System.err.println("Got unexpected confirm message: " + payload);
-                }
-            } else if (type.equals(DATA_TYPE_DISCONNECT)) {
-                if (state.get() == DISCONNECTED) {
-                    System.out.println("DISCONNECT: Already in disconnected: " + payload);
-                    return;
-                }
-                messages.addMessage(new Message(Message.MessageType.INFO,sender,reciever,payload));
-                System.out.println("DISCONNECT: " + payload);
-                this.setState(DISCONNECTED);
-            } else if (type.equals(DATA_TYPE_MESSAGE)) {
-                if (state.get() != CONNECTED) {
-                    System.out.println("MESSAGE: Illegal state " + state + " for message: " + payload);
-                    return;
-                }
-                messages.addMessage(new Message(Message.MessageType.MESSAGE,sender,reciever,payload));
-                System.out.println("MESSAGE: From " + sender + " to " + reciever + ": "+  payload);
-            } else if (type.equals(DATA_TYPE_ERROR)) {
-                messages.addMessage(new Message(Message.MessageType.ERROR,sender,reciever,payload));
-                System.out.println("ERROR: " + payload);
+            } else if (type.toString().equals(getDataTypeConfirm())) {
+                caseConfirm(sender.toString(), receiver.toString(), payload.toString());
+            } else if (type.toString().equals(getDataTypeDisconnect())) {
+                caseDisconnect(sender.toString(), receiver.toString(), payload.toString());
+            } else if (type.toString().equals(getDataTypeMessage())) {
+                caseMessage(sender.toString(), receiver.toString(), payload.toString());
+            } else if (type.toString().equals(getDataTypeError())) {
+                caseError(sender.toString(), receiver.toString(), payload.toString());
             } 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.get(), DATA_TYPE_ERROR, e.getMessage());
+            sendData(USER_NONE, userName.get(), getDataTypeError(), 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.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());
-            }
+    private void caseConfirm(String sender, String receiver, String payload) {
+        if (state.get() == CONFIRM_CONNECT) {
+            this.userName.set(receiver);
+            this.serverPort.set(getConnection().getRemotePort());
+            this.serverAddress.set(getConnection().getRemoteHost());
+            messages.addMessage(new Message(Message.MessageType.INFO, sender, receiver, payload));
+            System.out.println("CONFIRM: " + payload);
+            this.setState(CONNECTED);
+        } else if (state.get() == CONFIRM_DISCONNECT) {
+            messages.addMessage(new Message(Message.MessageType.INFO, sender, receiver, payload));
+            System.out.println("CONFIRM: " + payload);
+            this.setState(DISCONNECTED);
+        } else {
+            System.err.println("Got unexpected confirm message: " + payload);
         }
     }
 
+    /**
+     * Initiates the disconnect sequence and sends the message with all its info.
+     *
+     * @param sender   the sender name of the message
+     * @param receiver the receiver name of the message
+     * @param payload  the added payload that corresponds to the message
+     */
+    private void caseDisconnect(String sender, String receiver, String payload) {
+        if (state.get() == DISCONNECTED) {
+            System.out.println("DISCONNECT: Already in disconnected: " + payload);
+            return;
+        }
+        messages.addMessage(new Message(Message.MessageType.INFO, sender, receiver, payload));
+        System.out.println("DISCONNECT: " + payload);
+        this.setState(DISCONNECTED);
+    }
+
+    /**
+     * Initiates the procedure to send a new message and sends one as such.
+     *
+     * @param sender   the sender name of the message
+     * @param receiver the receiver name of the message
+     * @param payload  the added payload that corresponds to the message
+     */
+    private void caseMessage(String sender, String receiver, String payload) {
+        if (state.get() != CONNECTED) {
+            System.out.println("MESSAGE: Illegal state " + state + " for message: " + payload);
+            return;
+        }
+        messages.addMessage(new Message(Message.MessageType.MESSAGE, sender, receiver, payload));
+        System.out.println("MESSAGE: From " + sender + " to " + receiver + ": " + payload);
+    }
+
+    /**
+     * Stores the message as an error message and displays it as such as well.
+     *
+     * @param sender   the sender name of the message
+     * @param receiver the receiver name of the message
+     * @param payload  the added payload that corresponds to the message
+     */
+    private void caseError(String sender, String receiver, String payload) {
+        messages.addMessage(new Message(Message.MessageType.ERROR, sender, receiver, payload));
+        System.out.println("ERROR: " + payload);
+    }
+
+    /**
+     * 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.get() != NEW) throw new ChatProtocolException("Illegal state for connect: " + state);
-        this.sendData(userName.get(), 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.get() != NEW && state.get() != CONNECTED) throw new ChatProtocolException("Illegal state for disconnect: " + state);
-        this.sendData(userName.get(), USER_NONE, DATA_TYPE_DISCONNECT,null);
+        if (state.get() != NEW && state.get() != CONNECTED)
+            throw new ChatProtocolException("Illegal state for disconnect: " + state);
+        this.sendData(userName.get(), USER_NONE, getDataTypeDisconnect(), null);
         this.setState(CONFIRM_DISCONNECT);
     }
 
+    /**
+     * Sends message to Server
+     *
+     * @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);
 
@@ -218,15 +290,14 @@ public class ClientConnectionHandler implements Runnable {
         if (matcher.find()) {
             String receiver = matcher.group(1);
             String message = matcher.group(2);
-            if(message.length() < 1){
+            if (message.length() < 1) {
                 return false;
             }
             if (receiver == null || receiver.isBlank()) receiver = ClientConnectionHandler.USER_ALL;
-            this.sendData(userName.get(), receiver, DATA_TYPE_MESSAGE,message);
+            this.sendData(userName.get(), receiver, getDataTypeMessage(), message);
             return true;
         } else {
             return false;
         }
     }
-
 }

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

@@ -5,37 +5,63 @@ import javafx.beans.property.SimpleBooleanProperty;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * 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 List<Message> messages = new ArrayList<>();
-    private SimpleBooleanProperty changed = new SimpleBooleanProperty(false);
+    private final SimpleBooleanProperty changed = new SimpleBooleanProperty(false);
 
+    /**
+     * 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());
+        messages.add(message);
+        changed.set(!changed.get());
     }
 
-	public String getFilteredMessages(String filter) {
+    /**
+     * Applies a given filter over all messages and returns the result as a new String.
+     * Method is also in charge of applying the correct prefix to the message according to its type.
+     *
+     * @param filter is the applied filter on all the messages that are stored.
+     * @return String that matches the given filter.
+     */
+    public String getFilteredMessages(String filter) {
         StringBuilder result = new StringBuilder();
-		boolean showAll = filter == null || filter.isBlank();
-		for(Message message : messages) {
-			if(showAll || message.matchesFilter(filter))
-			{
+        boolean showAll = filter == null || filter.isBlank();
+        for (Message message : messages) {
+            if (showAll || message.matchesFilter(filter)) {
                 switch (message.getType()) {
-                    case MESSAGE -> result.append(String.format("[%s -> %s] %s\n", message.getSender(), message.getReceiver(), message.getText()));
+                    case MESSAGE ->
+                            result.append(String.format("[%s -> %s] %s\n", message.getSender(), message.getReceiver(), message.getText()));
                     case ERROR -> result.append(String.format("[ERROR] %s\n", message.getText()));
                     case INFO -> result.append(String.format("[INFO] %s\n", message.getText()));
-                    default -> result.append(String.format("[ERROR] %s\n", "Unexpected message type: " + message.getType()));
+                    default ->
+                            result.append(String.format("[ERROR] %s\n", "Unexpected message type: " + message.getType()));
                 }
-			}
-		}
+            }
+        }
         return result.toString();
-	}
+    }
 
+    /**
+     * Overwrites the Arraylist of messages, clearing it, also informs all Listeners.
+     */
     public void clear() {
         messages = new ArrayList<>();
         changed.set(!changed.get());
     }
 
-    public SimpleBooleanProperty getChangedProperty() { return changed; }
+    /**
+     * 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

@@ -6,14 +6,32 @@ 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 ClientMessageList clientMessageList = new ClientMessageList();
+    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"));
@@ -21,6 +39,7 @@ public class ClientUI extends Application {
 
             ChatWindowController chatWindowController = loader.getController();
             chatWindowController.setMessages(clientMessageList);
+            chatWindowController.setConnectionHandler(connectionHandler);
 
             // fill in scene and stage setup
             Scene scene = new Scene(rootPane);
@@ -32,7 +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/java/ch/zhaw/pm2/multichat/client/Message.java

@@ -1,20 +1,21 @@
 package ch.zhaw.pm2.multichat.client;
 
 /**
-A Message object represents one Message of a client. Can be stored in ClientMessageList.
+ * A Message object represents one Message of a client. Can be stored in ClientMessageList.
  */
 public class Message {
-    private MessageType type;
-    private String sender;
-    private String receiver;
-    private String text;
+    private final MessageType 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 reciever will be null)
-     * @param sender The User who has sent the message.
-     * @param receiver The User who should recieve the message.
-     * @param text The Text of the message.
+     *
+     * @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(MessageType type, String sender, String receiver, String text) {
         this.type = type;
@@ -24,14 +25,15 @@ public class Message {
     }
 
     /**
-     * Checks if the Filter String is contained in one of the datafields sender, receiver or 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 the Filter String is contained in a datafield.
+     * @return true if it is the Filter String is contained in a data field.
      */
-    public boolean matchesFilter(String filter){
+    public boolean matchesFilter(String filter) {
         return (sender != null && sender.contains(filter)) ||
-            (receiver != null && receiver.contains(filter)) ||
-            (text != null && text.contains(filter));
+                (receiver != null && receiver.contains(filter)) ||
+                (text != null && text.contains(filter));
     }
 
     /**
@@ -49,7 +51,7 @@ public class Message {
     }
 
     /**
-     * @return The Reciever who recieves the Message.
+     * @return The Receiver who receives the Message.
      */
     public String getReceiver() {
         return receiver;
@@ -63,7 +65,7 @@ public class Message {
     }
 
     /**
-     * Enummeration of Message Types.
+     * Enumeration of Message Types.
      */
     public enum MessageType {
         INFO, MESSAGE, ERROR;

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

@@ -12,74 +12,82 @@
 <?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">
-   <top>
-      <VBox BorderPane.alignment="CENTER">
-         <children>
-            <MenuBar>
-              <menus>
-                <Menu mnemonicParsing="false" text="Filter">
-                  <items>
-                    <MenuItem mnemonicParsing="false" text="press Enter">
-                           <graphic>
-                              <TextField fx:id="filterValue" onAction="#applyFilter" />
-                           </graphic>
-                        </MenuItem>
-                  </items>
-                </Menu>
-              </menus>
-            </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" />
-	            <Label alignment="CENTER" contentDisplay="CENTER" text="\@" textAlignment="CENTER" textOverrun="CLIP" HBox.hgrow="NEVER">
-	               <HBox.margin>
-	                  <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" />
-	            <Label text=":" HBox.hgrow="NEVER">
-	               <HBox.margin>
-	                  <Insets bottom="5.0" top="5.0" />
-	               </HBox.margin>
-	            </Label>
-	            <TextField fx:id="serverPortField" minWidth="-Infinity" prefWidth="60.0" promptText="Port" 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" />
-	               </HBox.margin>
-	            </Button>
-	         </children>
-	         <BorderPane.margin>
-	            <Insets />
-	         </BorderPane.margin>
-	         <padding>
-	            <Insets bottom="5.0" left="5.0" right="5.0" top="5.0" />
-	         </padding>
-	      </HBox>
-         </children>
-      </VBox>
-   </top>
-   <bottom>
-      <HBox spacing="5.0">
-         <children>
-            <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">
-               <HBox.margin>
-                  <Insets left="5.0" />
-               </HBox.margin>
-            </Button>
-         </children>
-         <padding>
-            <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" />
-         </BorderPane.margin>
-      </TextArea>
-   </center>
+<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>
+                <MenuBar>
+                    <menus>
+                        <Menu mnemonicParsing="false" text="Filter">
+                            <items>
+                                <MenuItem mnemonicParsing="false" text="press Enter">
+                                    <graphic>
+                                        <TextField fx:id="filterValue" onAction="#applyFilter"/>
+                                    </graphic>
+                                </MenuItem>
+                            </items>
+                        </Menu>
+                    </menus>
+                </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"/>
+                        <Label alignment="CENTER" contentDisplay="CENTER" text="\@" textAlignment="CENTER"
+                               textOverrun="CLIP" HBox.hgrow="NEVER">
+                            <HBox.margin>
+                                <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"/>
+                        <Label text=":" HBox.hgrow="NEVER">
+                            <HBox.margin>
+                                <Insets bottom="5.0" top="5.0"/>
+                            </HBox.margin>
+                        </Label>
+                        <TextField fx:id="serverPortField" minWidth="-Infinity" prefWidth="60.0" promptText="Port"
+                                   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"/>
+                            </HBox.margin>
+                        </Button>
+                    </children>
+                    <BorderPane.margin>
+                        <Insets/>
+                    </BorderPane.margin>
+                    <padding>
+                        <Insets bottom="5.0" left="5.0" right="5.0" top="5.0"/>
+                    </padding>
+                </HBox>
+            </children>
+        </VBox>
+    </top>
+    <bottom>
+        <HBox spacing="5.0">
+            <children>
+                <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">
+                    <HBox.margin>
+                        <Insets left="5.0"/>
+                    </HBox.margin>
+                </Button>
+            </children>
+            <padding>
+                <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"/>
+            </BorderPane.margin>
+        </TextArea>
+    </center>
 </BorderPane>

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

@@ -0,0 +1,142 @@
+package ch.zhaw.pm2.multichat.protocol;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.net.SocketException;
+import java.util.Scanner;
+
+/**
+ * This abstract class is the superclass for ClientConnectionHandler and ServerConnectionHandler
+ * It offers the DATA_TYPE Strings and a {@link State} enum for all valid connection states.
+ * Shared methods are implemented in this class as well {@link ConnectionHandler#sendData(String, String, String, String)} {@link ConnectionHandler#processData(Scanner, StringBuilder, StringBuilder, StringBuilder, StringBuilder)}
+ */
+public abstract class ConnectionHandler {
+    private NetworkHandler.NetworkConnection<String> connection;
+
+    // Data types used for the Chat Protocol
+    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 = "";
+    public static final String USER_ALL = "*";
+
+    // State of the connection
+    public enum State {
+        NEW, CONFIRM_CONNECT, CONNECTED, CONFIRM_DISCONNECT, DISCONNECTED, ERROR;
+    }
+
+    /**
+     * @return {@link ConnectionHandler#DATA_TYPE_CONNECT}
+     */
+    public static String getDataTypeConnect() {
+        return DATA_TYPE_CONNECT;
+    }
+
+    /**
+     * @return {@link ConnectionHandler#DATA_TYPE_CONFIRM}
+     */
+    public static String getDataTypeConfirm() {
+        return DATA_TYPE_CONFIRM;
+    }
+
+    /**
+     * @return {@link ConnectionHandler#DATA_TYPE_DISCONNECT}
+     */
+    public static String getDataTypeDisconnect() {
+        return DATA_TYPE_DISCONNECT;
+    }
+
+    /**
+     * @return {@link ConnectionHandler#DATA_TYPE_MESSAGE
+     */
+    public static String getDataTypeMessage() {
+        return DATA_TYPE_MESSAGE;
+    }
+
+    /**
+     * @return {@link ConnectionHandler#DATA_TYPE_ERROR}
+     */
+    public static String getDataTypeError() {
+        return 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 reads the data when a ConnectionHandler receives it. It tries to read out the sender, receiver, type and payload.
+     * If the data does not contain the expected number of lines, it throws a {@link ChatProtocolException}
+     *
+     * @param scanner  to read data
+     * @param sender   of the data
+     * @param receiver for the data
+     * @param type     of data
+     * @param payload  the data sent
+     * @throws ChatProtocolException if the data does not contain the expected number of lines
+     */
+    protected void processData(Scanner scanner, StringBuilder sender, StringBuilder receiver, StringBuilder type, StringBuilder payload) throws ChatProtocolException {
+        // parse data content
+        if (scanner.hasNextLine()) {
+            sender.append(scanner.nextLine());
+        } else if (scanner.hasNextLine()) {
+            receiver.append(scanner.nextLine());
+        } else {
+            throw new ChatProtocolException("No Sender found");
+        }
+        if (scanner.hasNextLine()) {
+            receiver.append(scanner.nextLine());
+        } else {
+            throw new ChatProtocolException("No Reciever found");
+        }
+        if (scanner.hasNextLine()) {
+            type.append(scanner.nextLine());
+        } else {
+            throw new ChatProtocolException("No Type found");
+        }
+        if (scanner.hasNextLine()) {
+            payload.append(scanner.nextLine());
+        }
+    }
+
+    /**
+     * 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, String type, String payload) {
+        if (connection.isAvailable()) {
+            String data = sender + "\n" +
+                    receiver + "\n" +
+                    type + "\n" +
+                    payload + "\n";
+            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());
+            }
+        }
+    }
+}

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

@@ -6,18 +6,40 @@ import java.io.IOException;
 import java.net.SocketException;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.ReentrantLock;
 
 
+/**
+ * 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 {
@@ -56,47 +78,30 @@ public class Server {
         }
     }
 
-    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());
-    }
-
+    /**
+     * With this methode the instance waits for incoming connections. If a client tries to connect to the server.
+     * The connection will be registered in the connection registry if successful.
+     */
     private void start() {
-        ReentrantLock mutex = new ReentrantLock();
-        Condition nameComplete = mutex.newCondition();
         System.out.println("Server started.");
         try {
             while (true) {
-                 NetworkHandler.NetworkConnection<String> connection = networkServer.waitForConnection();
-                 ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections, mutex, nameComplete);
-                 new Thread(connectionHandler).start();
-                 mutex.lock();
-                 try {
-                     nameComplete.await();
-                     System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
-                             connectionHandler.getUserName(),
-                             connection.getRemoteHost(),
-                             connection.getRemotePort()
-                     ));
-                 }
-                finally {
-                     mutex.unlock();
-                 }
+                NetworkHandler.NetworkConnection<String> connection = networkServer.waitForConnection();
+                ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections);
+                new Thread(connectionHandler).start();
             }
-        } catch(SocketException e) {
+        } catch (SocketException e) {
             System.out.println("Server connection terminated");
-        }
-        catch (IOException e) {
+        } catch (IOException e) {
             System.err.println("Communication error " + e);
-        } catch (InterruptedException e) {
-            throw new RuntimeException(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

@@ -1,206 +1,242 @@
 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.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.Condition;
 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 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 ReentrantLock mutex;
-
-    private Condition nameComplete;
-
-    private String userName = "Anonymous-"+connectionId;
+    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, ReentrantLock mutex, Condition nameComplete) {
+                                   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;
-        this.mutex = mutex;
-        this.nameComplete = nameComplete;
     }
 
-    public String getUserName() {
-        return this.userName;
-    }
-
-    public void startReceiving() {
-            System.out.println("Starting Connection Handler for new User");
-            try {
-                System.out.println("Start receiving data...");
-                while (connection.isAvailable()) {
-                    String data = connection.receive();
-                    processData(data);
-                }
-                System.out.println("Stopped recieving data");
-            } catch (SocketException e) {
-                System.out.println("Connection terminated locally");
-                connectionRegistry.remove(userName);
-                System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
-            } catch (EOFException e) {
-                System.out.println("Connection terminated by remote");
-                connectionRegistry.remove(userName);
-                System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
-            } catch (IOException e) {
-                System.err.println("Communication error: " + e);
-            } catch (ClassNotFoundException e) {
-                System.err.println("Received object of unknown type: " + e.getMessage());
+    /**
+     * 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.
+     */
+    private void startReceiving() {
+        System.out.println("Starting Connection Handler for new User");
+        try {
+            System.out.println("Start receiving data...");
+            while (getConnection().isAvailable() && !(state == ERROR)) {
+                String data = getConnection().receive();
+                processData(data);
             }
+            System.out.println("Stopped receiving data");
+        } catch (SocketException e) {
+            System.out.println("Connection terminated locally");
+            connectionRegistry.remove(userName);
+            System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
+        } catch (EOFException e) {
+            System.out.println("Connection terminated by remote");
+            connectionRegistry.remove(userName);
+            System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
+        } catch (IOException e) {
+            System.err.println("Communication error: " + 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(String data) {
         try {
-            // parse data content
             Scanner scanner = new Scanner(data);
-            String sender = null;
-            String reciever = null;
-            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();
-            }
+            StringBuilder sender = new StringBuilder();
+            StringBuilder receiver = new StringBuilder();
+            StringBuilder type = new StringBuilder();
+            StringBuilder payload = new StringBuilder();
+            super.processData(scanner, sender, receiver, type, payload);
 
             // dispatch operation based on type parameter
-            if (type.equals(DATA_TYPE_CONNECT)) {
-                if (this.state != NEW) throw new ChatProtocolException("Illegal state for connect request: " + state);
-                if (sender == null || sender.isBlank()) sender = this.userName;
-                if (connectionRegistry.containsKey(sender))
-                    throw new ChatProtocolException("User name already taken: " + sender);
-                mutex.lock();
-                try {
-                    this.userName = sender;
-                    nameComplete.signal();
-                }
-                finally {
-                    mutex.unlock();
-                }
-                connectionRegistry.put(userName, this);
-                sendData(USER_NONE, userName, DATA_TYPE_CONFIRM, "Registration successfull for " + userName);
-                this.state = CONNECTED;
-            } else if (type.equals(DATA_TYPE_CONFIRM)) {
+            if (type.toString().equals(getDataTypeConnect())) {
+                caseConnect(sender.toString());
+            } else if (type.toString().equals(getDataTypeConfirm())) {
                 System.out.println("Not expecting to receive a CONFIRM request from client");
-            } else if (type.equals(DATA_TYPE_DISCONNECT)) {
-                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);
-                this.state = DISCONNECTED;
-                this.stopReceiving();
-            } else if (type.equals(DATA_TYPE_MESSAGE)) {
-                if (state != CONNECTED) throw new ChatProtocolException("Illegal state for message request: " + state);
-                if (USER_ALL.equals(reciever)) {
-                    for (ServerConnectionHandler handler : connectionRegistry.values()) {
-                        handler.sendData(sender, reciever, type, payload);
-                    }
-                } else {
-                    ServerConnectionHandler handler = connectionRegistry.get(reciever);
-                    if (handler != null) {
-                        handler.sendData(sender, reciever, type, payload);
-                        if(!reciever.equals(sender)){
-                            sendData(sender, reciever, type, payload); //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);
-                    }
-                }
-            } else if (type.equals(DATA_TYPE_ERROR)) {
+            } else if (type.toString().equals(getDataTypeDisconnect())) {
+                caseDisconnect();
+            } else if (type.toString().equals(getDataTypeMessage())) {
+                caseMessage(sender.toString(), receiver.toString(), type.toString(), payload.toString());
+            } else if (type.toString().equals(getDataTypeError())) {
                 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());
+        } catch (ChatProtocolException e) {
+            System.out.println("Error while processing data " + e.getMessage());
+            sendData(USER_NONE, userName, getDataTypeError(), 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());
+    /**
+     * This method is called by method {@link ServerConnectionHandler#processData(String)}
+     * Checks if username is valid. if valid sends response to client with confirmation.
+     *
+     * @param sender of the payload
+     * @throws ChatProtocolException if username not valid
+     */
+    private void caseConnect(String sender) throws ChatProtocolException {
+        if (this.state != NEW) throw new ChatProtocolException("Illegal state for connect request: " + state);
+        if (sender.isBlank()) sender = this.userName;
+        //if username not valid
+        if (connectionRegistry.containsKey(sender)) {
+            state = ERROR;
+            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: " + sender);
+        }
+        //if username valid
+        this.userName = sender;
+        connectionRegistry.put(userName, this);
+        sendData(USER_NONE, userName, getDataTypeConfirm(), "Registration successful for " + userName);
+        this.state = CONNECTED;
+        System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
+                userName,
+                getConnection().getRemoteHost(),
+                getConnection().getRemotePort()));
+    }
+
+    /**
+     * This method is called by method {@link ServerConnectionHandler#processData(String)}
+     * 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, getDataTypeConfirm(), "Confirm disconnect of " + userName);
+        this.state = DISCONNECTED;
+        this.stopReceiving();
+    }
+
+    /**
+     * This method is called by method {@link ServerConnectionHandler#processData(String)}
+     * Checks if broadcast or unicast. Sends data accordingly
+     *
+     * @param sender   who sent data
+     * @param receiver to receive data
+     * @param type     of message
+     * @param payload  data to transmit
+     * @throws ChatProtocolException if state not equal to CONNECT
+     */
+    private void caseMessage(String sender, String receiver, String type, String payload) throws ChatProtocolException {
+        if (state != CONNECTED) throw new ChatProtocolException("Illegal state for message request: " + state);
+        if (USER_ALL.equals(receiver)) {
+            for (ServerConnectionHandler handler : connectionRegistry.values()) {
+                handler.sendData(sender, receiver, type, payload);
+            }
+        } else {
+            ServerConnectionHandler handler = connectionRegistry.get(receiver);
+            if (handler != null) {
+                handler.sendData(sender, receiver, type, payload);
+                if (!receiver.equals(sender)) {
+                    sendData(sender, receiver, type, payload); //send message to sender if it's a direct message and sender is not receiver.
+                }
+            } else {
+                this.sendData(USER_NONE, userName, getDataTypeError(), "Unknown User: " + receiver);
             }
         }
     }