Programmation client serveur avec les sockets : factoriel d'un nombre

La classe client 

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Client {

    public static void main(String args[]) {
        try {
            Socket socket = new Socket(InetAddress.getLocalHost(), 2009);
            DataOutputStream out = new DataOutputStream(socket.getOutputStream();
            Scanner sc = new Scanner(System.in);
            System.out.print("Entrez un nombre : ");
            int number = sc.nextInt();
            out.writeInt(number);
            out.flush();
            DataInputStream in = new DataInputStream(socket.getInputStream());
            System.out.println("\nfact(" + number + ") = " + in.readLong());
        } catch (UnknownHostException ex) {
            ex.printStackTrace();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

 La classe Serveur

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Server {

    private static long factoriel(int n) {
        if (n == 0 || n == 1) {
            return 1;
        } else if (n == 2) {
            return 2;
        } else {
            return n * factoriel(n - 1);
        }
    }

    public static void main(String args[]) {
        try {
            ServerSocket server = new ServerSocket(2009);
            Socket socket = server.accept();
            DataInputStream in = new DataInputStream(socket.getInputStream());
            int number = in.readInt();
            System.out.println("Nombre reçu sur le serveur = " + number);
            DataOutputStream out = new DataOutputStream(socket.getOutputStream())
            out.writeLong(factoriel(number));
            out.flush();
            out.close();
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}