Here i create the Connection instance

                    Socket connection = server.accept();

                    ObjectOutputStream output = new ObjectOutputStream(connection.getOutputStream());
                    ObjectInputStream input = new ObjectInputStream(connection.getInputStream());

                    username = (String) input.readObject();

                    output.writeObject("Willkommen!");
                    output.flush();

                    Connection connectionClass = new Connection(username, connection, output, input);