TCP

public class Client {
      public static void main(String[] args){
        try{
          Socket socket = new Socket("localhost", 1337);
          PrintWriter data_to_server = new PrintWriter(socket.getOutputStream(), true);
          BufferedReader data_from_server =
                  new BufferedReader(
                            new InputStreamReader(socket.getInputStream()));
          //Send message to server
          data_to_server.println("MSG FROM CLIENT");
          //Erhalte jeweilige Antwort
          String msg = data_from_server.readLine();
          System.out.println("Data from Server : " + msg);
          socket.close();
        }catch(IOException ioe){
          ioe.printStackTrace();
        }
      }
    }

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket server = new ServerSocket(1337);

        while (true) {
            //Waiting for client to connect
            System.out.println("Waiting for client to connect...");
            Socket socket = server.accept();
            //Writer for the answer
            PrintWriter data_to_client = new PrintWriter(
                    socket.getOutputStream(), true);
            //Reader for incoming message
            BufferedReader data_from_client = new BufferedReader(
                    new InputStreamReader(socket.getInputStream()));

            //Adress of client
            InetAddress remoteIp = socket.getInetAddress();
            //Getting the message
            String msg = data_from_client.readLine();
            data_to_client.println("DATA FROM SERVER");
            System.out.println("Client " + remoteIp + " : " + msg);
        }
    }
}