Le protocole SMTP: proxy java

import java.io.*;
import java.net.*;

class OneServeur extends Thread{
  private Socket socket, socketToSMTP;
  private BufferedReader fromMailer;
  private PrintWriter toMailer;
  private PrintWriter toSMTP;
  private BufferedReader fromSMTP;

  public OneServeur(Socket s) throws IOException {
        socket = s;
        fromMailer = new BufferedReader( new InputStreamReader (
                                          socket.getInputStream()));
        toMailer = new PrintWriter( new BufferedWriter (
                                      new OutputStreamWriter (
                                        socket.getOutputStream())),true);

        socketToSMTP = new Socket(InetAddress.getByName("SMTP SERVEUR"),25);
        System.out.println(socketToSMTP);
        fromSMTP = new BufferedReader( new InputStreamReader (
                                        socketToSMTP.getInputStream()));
        toSMTP = new PrintWriter( new BufferedWriter (
                                    new OutputStreamWriter (
                                      socketToSMTP.getOutputStream())),true);

        start();
  }

  public void run() {
    try {
        String str;
        while(true) {

             str = fromSMTP.readLine();
             if ( str == null ) break;
             toMailer.println(str);
             System.out.println(str);

             if ( str.startsWith("354") ) { // data 

              do {
                str = fromMailer.readLine();
                if ( str == null ) break;
                toSMTP.println(str);
                System.out.println(str);
              } while ( !str.startsWith(".") );

              if ( str == null ) break;

             } else  {
                 str = fromMailer.readLine();
                 if ( str == null ) break;
                 toSMTP.println(str);
                 System.out.println(str);
             }
        }
        System.out.println("\nclosing ...");
    } catch ( IOException e) {
    } finally {
        try {
                socket.close();
        } catch ( IOException e ) {}
    }
  }
}

public class Proxy {

  public static final int PORT = 25;

  public static void main(String args[]) throws IOException {
        ServerSocket s = new ServerSocket(PORT);
        System.out.println("Started " + s);

        try {
                while ( true ) {
                        Socket socket = s.accept();
                        try {
                                System.out.println("connection acceptee " +
                                                    socket);
                                new OneServeur(socket);
                        } catch ( IOException e ) {
                                socket.close();
                        }
                }
        } finally {
                s.close();
        }
  }
}