fixed issue #39

Continue connectionhandler

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

@@ -2,8 +2,6 @@ package ch.zhaw.pm2.multichat.client;
 
 import ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State;
 import ch.zhaw.pm2.multichat.protocol.ChatProtocolException;
-import ch.zhaw.pm2.multichat.protocol.ConnectionHandler;
-import ch.zhaw.pm2.multichat.protocol.NetworkHandler;
 import javafx.application.Platform;
 import javafx.beans.value.ChangeListener;
 import javafx.beans.value.ObservableValue;
@@ -36,12 +34,6 @@ public class ChatWindowController {
     @FXML private TextField filterValue;
 
 
-    @FXML
-    public void initialize() {
-        serverAddressField.setText(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
-        serverPortField.setText(String.valueOf(NetworkHandler.DEFAULT_PORT));
-    }
-
     public void setMessages(ClientMessageList messages) {
         this.messages = messages;
         messageListener();
@@ -49,6 +41,9 @@ public class ChatWindowController {
 
     public void setConnectionHandler(ClientConnectionHandler connectionHandler){
         this.connectionHandler = connectionHandler;
+        startConnectionHandlerListener();
+        serverAddressField.setText(connectionHandler.getServerAddressProperty().get());
+        serverPortField.setText(String.valueOf(connectionHandler.getServerPortProperty().get()));
     }
 
     private void applicationClose() {
@@ -104,7 +99,7 @@ public class ChatWindowController {
 
     @FXML
     private void applyFilter( ) {
-    	this.redrawMessageList();
+        Platform.runLater(() -> this.messageArea.setText(messages.getFilteredMessages(filterValue.getText().strip())));
     }
 
     private void startConnectionHandler() throws IOException {
@@ -116,7 +111,7 @@ public class ChatWindowController {
             new Thread(connectionHandler).start();
 
             //register Listener
-            startListener();
+            //startConnectionHandlerListener();
 
             // register window close handler
             rootPane.getScene().getWindow().addEventHandler(WindowEvent.WINDOW_CLOSE_REQUEST, windowCloseHandler);
@@ -169,19 +164,13 @@ public class ChatWindowController {
         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())));
-    }
-
     class WindowCloseHandler implements EventHandler<WindowEvent> {
         public void handle(WindowEvent event) {
             applicationClose();
         }
-
     }
 
-    public void startListener() {
+    public void startConnectionHandlerListener() {
         connectionHandler.getStateProperty().addListener(new ChangeListener<State>() {
             @Override
             public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
@@ -215,7 +204,7 @@ public class ChatWindowController {
         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/ClientConnectionHandler.java

@@ -29,21 +29,17 @@ public class ClientConnectionHandler extends ConnectionHandler implements Runnab
         super();
         this.messages = messages;
         state = new SimpleObjectProperty<>(State.NEW);
-        serverAddress = new SimpleStringProperty();
-        serverPort = new SimpleIntegerProperty();
+        serverAddress = new SimpleStringProperty(NetworkHandler.DEFAULT_ADDRESS.getCanonicalHostName());
+        serverPort = new SimpleIntegerProperty(NetworkHandler.DEFAULT_PORT);
+        this.userName = new SimpleStringProperty(null);
     }
 
     public void initialize(String serverAddress, int serverPort, String userName) throws IOException {
-        this.state = new SimpleObjectProperty<>(NEW);
-        this.serverAddress = new SimpleStringProperty(serverAddress);
-        this.serverPort = new SimpleIntegerProperty(serverPort);
+        state.set(NEW);
+        this.serverAddress.set(serverAddress);
+        this.serverPort.set(serverPort);
+        setConnection(NetworkHandler.openConnection(serverAddress, serverPort));
         this.userName = new SimpleStringProperty((userName == null || userName.isBlank())? USER_NONE : userName);
-        try {
-            setConnection(NetworkHandler.openConnection(this.serverAddress.get(), this.serverPort.get()));
-        } catch (IOException e) {
-            messages.addMessage(new Message(Message.MessageType.ERROR,null,null,e.getMessage()));
-            System.out.println("ERROR: " + e.getMessage());
-        }
     }
 
     public SimpleStringProperty getServerAddressProperty() { return serverAddress; }
@@ -103,66 +99,24 @@ public class ClientConnectionHandler extends ConnectionHandler implements Runnab
 
     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 reciever = new StringBuilder();
+            StringBuilder type = new StringBuilder();
+            StringBuilder payload = new StringBuilder();
+            super.processData(scanner,sender,reciever,type,payload);
+
             // dispatch operation based on type parameter
-            if (type.equals(getDataTypeConnect())) {
+            if (type.toString().equals(getDataTypeConnect())) {
                 System.err.println("Illegal connect request from server");
-            } else if (type.equals(getDataTypeConfirm())) {
-                if (state.get() == CONFIRM_CONNECT) {
-                    this.userName.set(reciever);
-                    this.serverPort.set(getConnection().getRemotePort());
-                    this.serverAddress.set(getConnection().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(getDataTypeDisconnect())) {
-                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(getDataTypeMessage())) {
-                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(getDataTypeError())) {
-                messages.addMessage(new Message(Message.MessageType.ERROR,sender,reciever,payload));
-                System.out.println("ERROR: " + payload);
+            } else if (type.toString().equals(getDataTypeConfirm())) {
+                caseConfirm(sender.toString(), reciever.toString(), payload.toString());
+            } else if (type.toString().equals(getDataTypeDisconnect())) {
+                caseDisconnect(sender.toString(),reciever.toString(),payload.toString());
+            } else if (type.toString().equals(getDataTypeMessage())) {
+                caseMessage(sender.toString(),reciever.toString(),payload.toString());
+            } else if (type.toString().equals(getDataTypeError())) {
+                caseError(sender.toString(), reciever.toString(), payload.toString());
             } else {
                 System.out.println("Unknown data type received: " + type);
             }
@@ -172,27 +126,47 @@ public class ClientConnectionHandler extends ConnectionHandler implements Runnab
         }
     }
 
-    private void sendData(String sender, String receiver, String type, String payload) {
-        if (getConnection().isAvailable()) {
-            new StringBuilder();
-            String data = new StringBuilder()
-                .append(sender+"\n")
-                .append(receiver+"\n")
-                .append(type+"\n")
-                .append(payload+"\n")
-                .toString();
-            try {
-                getConnection().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 reciever, String payload) {
+        if (state.get() == CONFIRM_CONNECT) {
+            this.userName.set(reciever);
+            this.serverPort.set(getConnection().getRemotePort());
+            this.serverAddress.set(getConnection().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);
         }
     }
 
+    private void caseDisconnect(String sender, String reciever, String payload) {
+        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);
+    }
+
+    private void caseMessage(String sender, String reciever, 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,reciever,payload));
+        System.out.println("MESSAGE: From " + sender + " to " + reciever + ": "+  payload);
+    }
+
+    private void caseError(String sender, String reciever, String payload) {
+        messages.addMessage(new Message(Message.MessageType.ERROR,sender,reciever,payload));
+        System.out.println("ERROR: " + payload);
+    }
+
     public void connect() throws ChatProtocolException {
         if (state.get() != NEW) throw new ChatProtocolException("Illegal state for connect: " + state);
         this.sendData(userName.get(), USER_NONE, getDataTypeConnect(),null);
@@ -222,5 +196,4 @@ public class ClientConnectionHandler extends ConnectionHandler implements Runnab
             return false;
         }
     }
-
 }

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

@@ -1,5 +1,10 @@
 package ch.zhaw.pm2.multichat.protocol;
 
+import java.io.EOFException;
+import java.io.IOException;
+import java.net.SocketException;
+import java.util.Scanner;
+
 public abstract class ConnectionHandler {
     private NetworkHandler.NetworkConnection<String> connection;
 
@@ -44,4 +49,47 @@ public abstract class ConnectionHandler {
     protected void setConnection(NetworkHandler.NetworkConnection<String> connection) {
         this.connection = connection;
     }
+
+    protected void processData(Scanner scanner, StringBuilder sender, StringBuilder reciever, StringBuilder type, StringBuilder payload) throws ChatProtocolException {
+        // parse data content
+        if (scanner.hasNextLine()) {
+            sender.append(scanner.nextLine());
+        } else {
+            throw new ChatProtocolException("No Sender found");
+        }
+        if (scanner.hasNextLine()) {
+            reciever.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());
+        }
+    }
+
+    protected 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 {
+                getConnection().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

@@ -10,7 +10,15 @@ 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 conections will be atached to a Connectionhandler: {@link ServerConnectionHandler} and placed in a Map containing all active connections {@link Server#connections}
+ *
+ */
 public class Server {
 
     // Server connection
@@ -57,6 +65,11 @@ public class Server {
         }
     }
 
+    /**
+     * 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");
@@ -64,6 +77,10 @@ public class Server {
         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();
@@ -73,37 +90,19 @@ public class Server {
                  NetworkHandler.NetworkConnection<String> connection = networkServer.waitForConnection();
                  ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections, mutex, nameComplete);
                  new Thread(connectionHandler).start();
-                 mutex.lock();
-                 try {
-                     nameComplete.await();
-                     if(connectionHandler.getState() == ConnectionHandler.State.ERROR) {
-                         System.out.println(String.format("Connecting failed for new Client with IP:Port <%s:%d>.\nReason: Name already taken.",
-                                 connection.getRemoteHost(),
-                                 connection.getRemotePort()));
-                     }
-                     else {
-                         System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
-                                 connectionHandler.getUserName(),
-                                 connection.getRemoteHost(),
-                                 connection.getRemotePort()));
-                     }
-                 }
-                finally {
-                     mutex.unlock();
-                 }
             }
         } 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

@@ -8,7 +8,6 @@ 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;
@@ -17,7 +16,31 @@ import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.ReentrantLock;
 
 
-
+/**
+ * This class represents the connection between the server and a client and offers the serverside logic.
+ * The ServerConnectionHandler receives data send from the client aswell as sends data to the client.
+ *
+ * The ServeConnectionHandler offers following functionality:
+ *
+ * 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}
+ *
+ * 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()}
+ *
+ * Processes Messages send from a client by:
+ * 1. Evaluating the reciever by differentiating between broadcast or unicast.
+ * 2. Sending the message accordingly.
+ *
+ * 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();
@@ -30,11 +53,21 @@ public class ServerConnectionHandler extends ConnectionHandler implements Runnab
     private String userName = "Anonymous-"+connectionId;
     private State state = NEW;
 
+    /**
+     * Called when runnable gets started in a thread.
+     */
     @Override
     public void run() {
         startReceiving();
     }
 
+    /**
+     * Constructor to intitialize the connection
+     * @param connection representing the socket connection between server and clinet
+     * @param registry map containing all active connections between server and clients
+     * @param mutex to lock thread
+     * @param nameComplete condition to call threads
+     */
     public ServerConnectionHandler(NetworkHandler.NetworkConnection<String> connection,
                                    Map<String,ServerConnectionHandler> registry, ReentrantLock mutex, Condition nameComplete) {
         super();
@@ -46,14 +79,26 @@ public class ServerConnectionHandler extends ConnectionHandler implements Runnab
         this.nameComplete = nameComplete;
     }
 
+    /**
+     *
+     * @return the username of the connected client
+     */
     public String getUserName() {
         return this.userName;
     }
 
+    /**
+     *
+     * @return state of the connection. Poosible states are see {@link ch.zhaw.pm2.multichat.protocol.ConnectionHandler.State}
+     */
     public State getState() {
         return state;
     }
 
+    /**
+     * This methods runs in a whileloop 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 {
@@ -84,6 +129,9 @@ public class ServerConnectionHandler extends ConnectionHandler implements Runnab
 
     }
 
+    /**
+     * This method will call {@link NetworkHandler.NetworkConnection#close()} to close the Socket.
+     */
     private void stopReceiving() {
         System.out.println("Closing Connection Handler for " + userName);
         try {
@@ -91,93 +139,41 @@ public class ServerConnectionHandler extends ConnectionHandler implements Runnab
             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);
     }
 
+    /**
+     * This method gets called when socket recieves 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 recieve 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 recieved 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 reciever = new StringBuilder();
+            StringBuilder type = new StringBuilder();
+            StringBuilder payload = new StringBuilder();
+            super.processData(scanner,sender,reciever,type,payload);
 
             // dispatch operation based on type parameter
-            if (type.equals(getDataTypeConnect())) {
-                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)) {
-                    mutex.lock();
-                    try {
-                        state = ERROR;
-                        nameComplete.signal();
-                    }
-                    finally {
-                        mutex.unlock();
-                    }
-                    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, getDataTypeConfirm(), "Registration successfull for " + userName);
-                this.state = CONNECTED;
-            } else if (type.equals(getDataTypeConfirm())) {
+            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(getDataTypeDisconnect())) {
-                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();
-            } else if (type.equals(getDataTypeMessage())) {
-                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, getDataTypeError(), "Unknown User: " + reciever);
-                    }
-                }
-            } else if (type.equals(getDataTypeError())) {
+            } else if (type.toString().equals(getDataTypeDisconnect())) {
+                caseDisconnect();
+            } else if (type.toString().equals(getDataTypeMessage())) {
+                caseMessage(sender.toString(), reciever.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);
@@ -189,25 +185,74 @@ public class ServerConnectionHandler extends ConnectionHandler implements Runnab
         }
     }
 
+    /**
+     * 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 successfull 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 allready 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();
+    }
 
-    private void sendData(String sender, String receiver, String type, String payload) {
-        if (getConnection().isAvailable()) {
-            new StringBuilder();
-            String data = new StringBuilder()
-                .append(sender+"\n")
-                .append(receiver+"\n")
-                .append(type+"\n")
-                .append(payload+"\n")
-                .toString();
-            try {
-                getConnection().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 broadcast or unicast. Sends data accordingly
+     * @param sender who sent data
+     * @param reciever to recieve data
+     * @param type of message
+     * @param payload data to transmit
+     * @throws ChatProtocolException if state not equal to CONNECT
+     */
+    private void caseMessage(String sender, String reciever, String type, String payload) throws ChatProtocolException{
+        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, getDataTypeError(), "Unknown User: " + reciever);
             }
         }
     }