public class Server {
    public static void main(String[] args) {
        int port = 8080;

        try (ServerSocket serverSocket = new ServerSocket(port)) {

            System.out.println("Server is listening on port " + port);

            while (true) {
                Socket socket = serverSocket.accept();
                System.out.println("New client connected");

                InputStream input = socket.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(input));

                OutputStream output = socket.getOutputStream();
                PrintWriter writer = new PrintWriter(output, true);


                String text;

                do {
                    text = reader.readLine();
                    String reverseText = new StringBuilder(text).reverse().toString();
                    writer.println("Server: " + reverseText);

                } while (!text.equals("bye"));

                socket.close();
            }

        } catch (IOException ex) {
            System.out.println("Server exception: " + ex.getMessage());
            ex.printStackTrace();
        }
    }
}

public class Client {
    public static void main(String[] args) {
        String hostname = "localhost";
        int port = 8080;
        try (Socket socket = new Socket(hostname, port)) {

            OutputStream output = socket.getOutputStream();
            PrintWriter writer = new PrintWriter(output, true);

            Console console = System.console();
            String text;

            do {
                text = console.readLine("Enter text: "); // Эта строчка NPO

                writer.println(text);

                InputStream input = socket.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(input));

                String time = reader.readLine();

                System.out.println(time);

            } while (!text.equals("bye"));

        } catch (UnknownHostException ex) {

            System.out.println("Server not found: " + ex.getMessage());

        } catch (IOException ex) {

            System.out.println("I/O error: " + ex.getMessage());
        }
    }
}