Get.java

import java.io.DataInputStream;
import java.io.IOException;
import java.net.*;

public class Get {

    public static void main(String[] args) {

        try {
            if (args.length > 3) {
                throw new ArrayIndexOutOfBoundsException();
            }
            InetAddress peerAddress = InetAddress.getByName(args[0]);
            int peerPort = Integer.parseInt(args[1]);
            int key = Integer.parseInt(args[2]);

            new Get(peerPort, peerAddress, key);

        } catch (UnknownHostException e) {
            System.out.println("The address " + args[1] + "does not seem to be a valid InetAddress");
            System.out.println("Otherwise you may not have access to the network at which the address is present");
        } catch (NumberFormatException | ArrayIndexOutOfBoundsException e) {
            System.out.println("parameters must be given as a port, an address and a key");
            System.out.println("Fx.: java Get localhost 8080 1");
        }
    }

    public Get(int peerPort, InetAddress peerAddress, int key) {
        try (ServerSocket serverSocket = new ServerSocket()) {
            serverSocket.bind(null);

            try {
                Socket peerSocket = new Socket(peerAddress, peerPort);
                Message getmessage = new Message(CodeType.Get, 
                    peerSocket.getLocalAddress().getHostAddress(), serverSocket.getLocalPort(), key);
                byte[] messageInBytes = getmessage.Serialize();

                peerSocket.getOutputStream().write(messageInBytes);
            } catch (IOException e) {
                System.out.println("failed to send get request: " + e.getMessage());
            }
            System.out.println("Listening on: " + serverSocket.getLocalPort());

            MessageListener mL = new MessageListener(serverSocket.accept());
            mL.start();
        } catch (IOException ex) {
            System.err.println("Server socker exception: " + ex.getMessage());
        }
    }
}