Enlisting Java in the War Against Email Viruses

class VirPro01a extends Frame{
  String dataPath = "./Messages/";

  int numberMsgs = 0;
  int msgCounter = 0;
  int msgNumber;
  String uidl = "";//unique POP3 msg ID
  BufferedReader inputStream;
  PrintWriter outputStream;
  Socket socket;
  String pathFileName;

Listing 1

  public static void main(String[] args){
    if(args.length != 3){
      System.out.println("Usage: java VirPro01a "
                + "pubServer userName password");
      System.exit(0);
    }//end if

    new VirPro01a(args[0],args[1],args[2]);
  }//end main

Listing 2

  VirPro01a(String server,String userName,
                                String password){
    int port = 110; //pop3 mail port
    try{
      //Get a socket, connected to the
      // specified server on the specified
      // port.
      socket = new Socket(server,port);

      //Get an input stream from the socket
      inputStream = new BufferedReader(
                     new InputStreamReader(
                       socket.getInputStream()));

      //Get  an output stream to the socket.
      outputStream = new PrintWriter(
               new OutputStreamWriter(
                 socket.getOutputStream()),true);

      //Display the msg received from the
      // server on the command line screen
      // immediately following connection.
      String connectMsg = validateOneLine();
      System.out.println("Connected to server "
                                   + connectMsg);

      //The communication process is now in the
      // AUTHORIZATION state.  Send the user
      // name and password to the server.
      //Commands are sent in plain text, upper
      // case to the server.  Some commands
      // require an argument following the
      // command, as is the case with USER.
      //Send the command.
      outputStream.println("USER " + userName);
      //Get response and confirm that the
      // response was +OK and was not -ERR.
      String userResponse = validateOneLine();
      //Display the response on the command-
      // line screen.
      System.out.println("USER " + userResponse);
      //Send the password to the server
      outputStream.println("PASS " + password);
      //Validate the server's response as +OK.
      // Display the response in the process.
      System.out.println(
                    "PASS " + validateOneLine());
    }catch(Exception e){e.printStackTrace();}

Listing 3

    this.addWindowListener(
      new WindowAdapter(){
        public void windowClosing(WindowEvent e){

          //Terminate the session with the
          // server.
          outputStream.println("QUIT");
          String quitResponse =
                               validateOneLine();
          //Display the response on the
          // command line screen.
          System.out.println(
                         "QUIT " + quitResponse);

          try{
            socket.close();
          }catch(Exception ex){
            System.out.println("\n" + ex);}

          System.exit(0);
        }//end windowClosing
      }//end WindowAdapter()
    );//end addWindowListener

Listing 4

    final Button startButton =
                        new Button("Start");
    final TextArea textArea =
                             new TextArea(20,50);

Listing 5

    startButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          try{
            //The communication process is now
            // in the TRANSACTION state.
            //Retrive and save messages
            if(numberMsgs == 0){
              outputStream.println("STAT");
              String stat = validateOneLine();
              //Get the number of messages as
              // a String.
              String numberMsgsStr =
                       stat.substring(
                          4,stat.indexOf(" ",5));
              //Convert the String to an int.
              numberMsgs = Integer.parseInt(
                                  numberMsgsStr);
            }//end if numberMsgs == 0
            //NOTE: Msg numbers begin with 1,
            // not 0.
            //Retrieve and save each
            // message.  Each msg ends with a
            // period on a new line.
            msgNumber = msgCounter + 1;
            if(msgNumber <= numberMsgs){
              //Process the next message.

              //Get and save a unique identifier
              // for the message from the server
              // and validate the response.
              outputStream.println(
                            "UIDL " + msgNumber);
              uidl = validateOneLine();

              //Open an output file to save
              // the message.  Use the UIDL
              // as the file name.
              pathFileName = dataPath + uidl;
              DataOutputStream dataOut =
                          new DataOutputStream(
                            new FileOutputStream(
                                  pathFileName));

              //Send a RETR command to begin
              // the message retrieval process
              outputStream.println(
                            "RETR " + msgNumber);
              //Validate the response.
              String retrResponse =
                               validateOneLine();

              //Read the first line in the
              // message from the server.
              String msgLine =
                          inputStream.readLine();

              //Continue reading lines until
              // a "." is encountered as the
              // first char in a line.  That
              // signals the end of the msg.
              while(!(msgLine.equals("."))){
                //Write the line to the output
                // file and read the next
                // line.  Insert newline
                // characters when writing the
                // output to the file.
                dataOut.writeBytes(
                                 msgLine + "\n");
                msgLine = inputStream.readLine();

              }//end while
              //Close the output file.  The
              // message is now stored in a
              // local file with a file name
              // based on the unique ID
              // provided by the server.
              dataOut.close();

              //Show progress
              textArea.append(msgNumber + "\n");

              //Increment the message counter
              // in preparation for
              // processing the next message.
              msgCounter++;

              //Disable this statement to require
              // the user to press the button
              // for each new message.
              Toolkit.getDefaultToolkit().
                     getSystemEventQueue().
                       postEvent(new ActionEvent(
                              startButton,
                              ActionEvent.
                                ACTION_PERFORMED,
                              "Start/Next"));

            }//end if msgNumber <= numberMsgs
            else{//msgNumber > numberMsgs
              //No more messages. Disable the
              //Start/Next button.
              startButton.setEnabled(false);

              //Alert the user
              Toolkit.getDefaultToolkit().beep();
              Thread.currentThread().sleep(300);
              Toolkit.getDefaultToolkit().beep();
              Thread.currentThread().sleep(300);
              Toolkit.getDefaultToolkit().beep();
            }//end else
          }//end try
          catch(Exception ex){
                         ex.printStackTrace();}
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

Listing 6

    add(startButton);
    add(textArea);
    textArea.setText("");
    setLayout(new FlowLayout());

    setTitle("Copyright 2004, R.G.Baldwin");
    setBounds(274,0,400,400);
    //Make the GUI visible.
    setVisible(true);
  }//end constructor

Listing 7

  private String readLines(String pathFileName,
               String firstLine,String lastLine){

Listing 8

    StringBuffer strBuf = new StringBuffer();
    try{
      BufferedReader inDataMsg
        = new BufferedReader(new FileReader(
                                  pathFileName));

      String data;
      boolean isSave = false;
      while((data = inDataMsg.readLine())
                                        != null){

        if(((firstLine == null) ||
                 (data.startsWith(firstLine))) &&
                              (isSave == false)){
          isSave = true;
        }//end if

        if(isSave){
          strBuf.append(data + "\n");
        }//end if

        if((lastLine != null) &&
                    (data.startsWith(lastLine))){
          break;//no need to read any more
        }//end if

      }//end while loop
      inDataMsg.close();//Close file
    }catch(Exception e){e.printStackTrace();}
    return new String(strBuf);
  }//end readLines

Listing 9

Return-Path: <Baldwin@DickBaldwin.com>
Received: from ms-smtp-01-eri0.texas.rr.com
 (ms-smtp-01.texas.rr.com [24.93.47.40])
	by omnistarhost.com (8.11.6/8.11.6)
 with ESMTP id i1G1PeX29829
	for <baldwin@dickbaldwin.com>; Sun,
 15 Feb 2004 19:25:40 -0600
Received: from DickBaldwin.com
 (cs24339-166.austin.rr.com [24.243.39.166])
	by ms-smtp-01-eri0.texas.rr.com
 (8.12.10/8.12.7) with ESMTP id i1G1JHLc003760
	for <baldwin@dickbaldwin.com>;
 Sun, 15 Feb 2004 19:19:20 -0600 (CST)
Message-ID: <40301A94.6070504@DickBaldwin.com>
Date: Sun, 15 Feb 2004 19:19:16 -0600
From: Richard Baldwin <Baldwin@DickBaldwin.com>
Reply-To: Baldwin@DickBaldwin.com
User-Agent: Mozilla/5.0 (Windows; U; Windows
 NT 5.1; en-US; rv:1.4) Gecko/20030624
 Netscape/7.1 (ax)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: baldwin@dickbaldwin.com
Subject: A test msg to illustrate message
 structure
Content-Type: text/plain;
 charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-MailScanner-Information: Please
 contact the ISP for more information
X-MailScanner: Found to be clean
Status:   

This is a test message.
-- 
Richard G. Baldwin (Dick Baldwin)
Home of Baldwin's on-line Java Tutorials
http://www.DickBaldwin.com

Professor of Computer Information Technology
Austin Community College
(512) 223-4758 or (512) 250-8682
mailto:Baldwin@DickBaldwin.com
http://www.austincc.edu/baldwin/

Figure 3

  private boolean forwardEmailMsg(
                            String recipient,
                            String smtpServer,
                            String tag,
                            String pathFileName){

Listing 10

      StringBuffer message = new StringBuffer(
                             "No message found");

Listing 11

      try{
        SmtpClient smtp =
                      new SmtpClient(smtpServer);

Listing 12

        smtp.from(recipient);

Listing 13

        smtp.to(recipient);

Listing 14

        PrintStream msg = smtp.startMessage();

Listing 15

        message = new StringBuffer(readLines(
                    pathFileName,null,null));

Listing 16

        message = message.insert(message.indexOf(
                             "Subject: ")+9,tag);

        msg.println(new String(message));

Listing 17

        //Close the stream and send the message
        smtp.closeServer();

        return true;
      }catch( Exception e ){
        System.out.println("\n" + e);
        System.out.println("Forwarding email");
        Toolkit.getDefaultToolkit().beep();
        try{
          Thread.currentThread().sleep(300);
        }catch(Exception ex){
          System.out.println(ex);
        }//end catch
        Toolkit.getDefaultToolkit().beep();
        return false;
      }//end catch

  }//end forwardEmailMsg

Listing 18

  private void moveFile(String pathFileName,
                             String archivePath){
    String fileName = pathFileName.substring(
              pathFileName.lastIndexOf('/') + 1);
    String archivePathFileName =
                          archivePath + fileName;

    boolean moved =
           new File(pathFileName).renameTo(
             new File(archivePathFileName));

    if(!moved)System.out.println(
      "Unable to move " + new File(pathFileName)
      + "\nto " + new File(archivePathFileName));
  }//end moveFile method

Listing 19

class VirPro01b extends Frame{
  //The following is the ID of the secret email
  // account provided as a command line parameter
  // when the program is started.
  String recipient;

  //The following is the local folder where
  // message files are stored awaiting virus
  // scanning and forwarding.  You may want to
  // change this to a different folder.
  String dataPath = "./Messages/";

  //The following is the local folder where the
  // messages are stored after they have been
  // scanned and forwarded to the secret email
  // account.  They are automatically moved to
  // this folder after being deleted from the
  // public email server. You will want to
  // manually empty this folder periodically.
  String archivePath = "./Archives/";

  //The following are working variables used by
  // the program for various purposes.
  BufferedReader inputStream;
  PrintWriter outputStream;
  Socket socket;
  String pathFileName;
  Vector msgToDelete = new Vector();

Listing 20

  public static void main(String[] args){
    if(args.length != 5){
      System.out.println("Usage: java VirPro01b "
                 + "pubServer userName password "
                 + "secretServer smtpServer");
      System.exit(0);
    }//end if

    new VirPro01b(args[0],args[1],args[2],
                                args[3],args[4]);
  }//end main

Listing 21

  VirPro01b(final String server,
            final String userName,
            final String password,
            String secretServer,
            final String smtpServer){

    recipient = secretServer;

Listing 22

    this.addWindowListener(
      new WindowAdapter(){
        public void windowClosing(WindowEvent e){
          System.exit(0);
        }//end windowClosing
      }//end WindowAdapter()
    );//end addWindowListener

Listing 23

    final Button startButton =
                        new Button("Start");
    final Button deleteButton = new Button(
                         "Delete Msg On Server");
    final TextArea textArea =
                             new TextArea(20,50);

Listing 24

    startButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          startButton.setEnabled(false);

          File dataDir = new File(dataPath);
          String[] dirList = dataDir.list();

Listing 25

          for(int msgCounter = 0;
                     msgCounter < dirList.length;
                                   msgCounter++){
            String fileName =
                             dirList[msgCounter];
            pathFileName = dataPath + fileName;

Listing 26

            String strMsgNumber =
                  pathFileName.substring(
                  pathFileName.indexOf(" "),
                  pathFileName.lastIndexOf(" ")).
                  trim();
            int msgNumber = Integer.parseInt(
                                   strMsgNumber);
            String msgNumberStr;
            if(msgNumber < 10){
              msgNumberStr = "00" + msgNumber;
            }else if(msgNumber > 99){
              msgNumberStr = "" + msgNumber;
            }else{
              msgNumberStr = "0" + msgNumber;
            }//end else

Listing 27

            boolean okToDelete =
                       forwardEmailMsg(
                          recipient,
                          smtpServer,
                          "{"+ msgNumberStr +"}",
                          pathFileName);

Listing 28

            if(okToDelete){
              textArea.append("Forwarded " +
                            msgNumberStr + "\n");
              msgToDelete.add(pathFileName);
            }else{
              textArea.append("Failed " +
                            msgNumberStr + "\n");
            }//end else
          }//end for loop on directory length

Listing 29

          deleteButton.setEnabled(true);
          textArea.append("\nDo you want to "
             + "delete messages from server?\n");

Listing 30

          try{
            Toolkit.getDefaultToolkit().beep();
            Thread.currentThread().sleep(300);
            Toolkit.getDefaultToolkit().beep();
            Thread.currentThread().sleep(300);
            Toolkit.getDefaultToolkit().beep();
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

Listing 31

    deleteButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          deleteButton.setEnabled(false);
          textArea.append("\n");

Listing 32

          int port = 110; //pop3 mail port
          try{
            //Get a socket, connected to the
            // specified server on the specified
            // port.
            socket = new Socket(server,port);

            //Get an input stream from the socket
            inputStream = new BufferedReader(
                     new InputStreamReader(
                       socket.getInputStream()));

            //Get an output stream to the socket.
            outputStream = new PrintWriter(
                     new OutputStreamWriter(
                       socket.getOutputStream()),
                                           true);

            //Display the msg received from the
            // server on the command line screen
            // immediately following connection.
            String connectMsg =
                               validateOneLine();
            System.out.println(
                           "Connected to server "
                                   + connectMsg);

            //The communication process is now in
            // the AUTHORIZATION state.  Send the
            // user name and password to the
            // server.
            //Commands are sent in plain text,
            // upper case to the server.  Some
            // commands require an argument
            // following the command, as is the
            // case with USER.
            //Send the command.
            outputStream.println("USER "
                                     + userName);
            //Get response and confirm that the
            // response was +OK and was not -ERR.
            String userResponse =
                               validateOneLine();
            //Display the response on the
            // command line screen.
            System.out.println("USER "
                                 + userResponse);
            //Send the password to the server
            outputStream.println("PASS "
                                     + password);
            //Validate the server's response as
            // +OK. Display the response in the
            // process.
            System.out.println("PASS "
                            + validateOneLine());
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch

Listing 33

          for(int cnt = 0;
                 cnt < msgToDelete.size();cnt++){
            pathFileName =
              (String)msgToDelete.elementAt(cnt);
            String strMsgNumber =
                pathFileName.substring(
                 pathFileName.indexOf(" "),
                  pathFileName.lastIndexOf(" ")).
                   trim();
            int msgNumber = Integer.parseInt(
                                   strMsgNumber);

Listing 34

System.out.println(
            "Deletion is temporarily disabled.");
/*Deletion from the server temporarily disabled.
 *Do not enable this deletion code until you
 * understand exactly what you are doing.
            outputStream.println(
                            "DELE " + msgNumber);

            //Validate the response and display
            // it on the GUI.
            textArea.append(
                       "Msg: " + msgNumber + " "
                       + validateOneLine()+"\n");
            textArea.append(
                   "Marked:" + msgNumber + "\n");
*/

Listing 35

            moveFile(pathFileName,archivePath);

          }//end for loop on msgToDelete.size()

Listing 36

          outputStream.println("QUIT");
          String quitResponse =
                               validateOneLine();
          System.out.println(
                         "QUIT " + quitResponse);

Listing 37

          try{
            socket.close();
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch

          textArea.append("\n\nMessages deleted "
                             + "from server.\n");
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

Listing 38

    add(startButton);
    add(deleteButton);
    deleteButton.setEnabled(false);
    add(textArea);
    textArea.setText("");
    setLayout(new FlowLayout());

    setTitle("Copyright 2004, R.G.Baldwin");
    setBounds(274,0,400,400);
    //Make the GUI visible.
    setVisible(true);
  }//end constructor
}//end class VirPro01b

Listing 39

/*File VirPro01a.java Copyright 2004, R.G.Baldwin
Rev 02/14/04

This is one of a pair of programs designed to be
used together, in conjunction with a good virus
scanner program to prevent messages with viruses
from contaminating an email inbox.

This program should be run before the program
named VirPro01b. This program downloads all the
messages on a POP3 email server and stores each
message in a separate file in a folder on the
local disk.

After this program has been run, the user should
use a good virus checker to scan all of those
files, removing any that contain a virus.

After scanning the files, the user should run
VirPro01b to forward the remaining clean messages
to a secret email account.  After forwarding the
messages to the secret email account, the user is
given an opportunity to delete those messages
from the public email server, and to move the
local files containing the messages from the
working directory into an archive directory.

If there is any question as to whether a
message was successfully forwarded, (as might
be the case under bad network conditions), that
message is not deleted from the server and is not
moved to the archive folder.  It remains in the
working folder so that the user can run
VirPro01b again in an attempt to successfully
forward that message and any other messages
remaining in the working folder to the secret
email account.

On my system with a cable modem, about three to
four seconds are required to forward each message
to my secret email account.

This program is designed to be used with a POP3
email server.  For technical information on POP3,
see RFC 1725 at
http://www.cis.ohio-state.edu/htbin/rfc/rfc1725.
html

A POP3 Command Summary follows based on the
information at that web site.

Minimal POP3 Commands:
USER name
PASS string
QUIT
STAT
LIST [msg]
RETR msg
DELE msg
NOOP
RSET
QUIT

Optional POP3 Commands:
APOP name digest
TOP msg n
UIDL [msg]

POP3 Replies:
+OK
-ERR

Usage:  Enter the following at the command line:
java VirPro01a pubServer userName password

where the command line parameters identify your
public email server, your user name, and your
password on that email server.

Tested using SDK 1.4.2 under WinXP
************************************************/

import java.net.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;

class VirPro01a extends Frame{
  //The following is the local working folder
  // where message files are stored awaiting
  // scanning and forwarding. You might want to
  // use a different folder for this purpose. If
  // so, simply provide the path and folder name
  // as a string.
  String dataPath = "./Messages/";

  //The following are working variables used by
  // the program for various purposes.
  int numberMsgs = 0;
  int msgCounter = 0;
  int msgNumber;
  String uidl = "";//unique POP3 msg ID
  BufferedReader inputStream;
  PrintWriter outputStream;
  Socket socket;
  String pathFileName;

  public static void main(String[] args){
    if(args.length != 3){
      System.out.println("Usage: java VirPro01a "
                + "pubServer userName password");
      System.exit(0);
    }//end if

    new VirPro01a(args[0],args[1],args[2]);
  }//end main
  //===========================================//

  //Constructor
  VirPro01a(String server,String userName,
                                String password){
    int port = 110; //pop3 mail port
    try{
      //Get a socket, connected to the
      // specified server on the specified
      // port.
      socket = new Socket(server,port);

      //Get an input stream from the socket
      inputStream = new BufferedReader(
                     new InputStreamReader(
                       socket.getInputStream()));

      //Get  an output stream to the socket.
      // Note that this stream will autoflush.
      outputStream = new PrintWriter(
               new OutputStreamWriter(
                 socket.getOutputStream()),true);

      //Display the msg received from the
      // server on the command line screen
      // immediately following connection.
      String connectMsg = validateOneLine();
      System.out.println("Connected to server "
                                   + connectMsg);

      //The communication process is now in the
      // AUTHORIZATION state.  Send the user
      // name and password to the server.
      //Commands are sent in plain text, upper
      // case to the server.  Some commands
      // require an argument following the
      // command, as is the case with USER.
      //Send the command.
      outputStream.println("USER " + userName);
      //Get response and confirm that the
      // response was +OK and was not -ERR.
      String userResponse = validateOneLine();
      //Display the response on the command-
      // line screen.
      System.out.println("USER " + userResponse);
      //Send the password to the server
      outputStream.println("PASS " + password);
      //Validate the server's response as +OK.
      // Display the response in the process.
      System.out.println(
                    "PASS " + validateOneLine());
    }catch(Exception e){e.printStackTrace();}

    //Register a window listener to service
    // the close button on the Frame.
    this.addWindowListener(
      new WindowAdapter(){
        public void windowClosing(WindowEvent e){

          //Terminate the session with the
          // server.
          outputStream.println("QUIT");
          String quitResponse =
                               validateOneLine();
          //Display the response on the
          // command line screen.
          System.out.println(
                         "QUIT " + quitResponse);

          try{
            socket.close();
          }catch(Exception ex){
            System.out.println("\n" + ex);}

          System.exit(0);
        }//end windowClosing
      }//end WindowAdapter()
    );//end addWindowListener

    //Note that the compiler requires the
    // reference to the following components to
    // be final because they are accessed from
    // within an anonymous class definition.
    final Button startButton =
                        new Button("Start");
    final TextArea textArea =
                             new TextArea(20,50);

    //Register an ActionListener on the
    // startButton.
    startButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          try{
            //The communication process is now
            // in the TRANSACTION state.
            //Retrive and save messages
            if(numberMsgs == 0){
              outputStream.println("STAT");
              String stat = validateOneLine();
              //Get the number of messages as
              // a String.
              String numberMsgsStr =
                       stat.substring(
                          4,stat.indexOf(" ",5));
              //Convert the String to an int.
              numberMsgs = Integer.parseInt(
                                  numberMsgsStr);
            }//end if numberMsgs == 0
            //NOTE: Msg numbers begin with 1,
            // not 0.
            //Retrieve and save each
            // message.  Each msg ends with a
            // period on a new line.
            msgNumber = msgCounter + 1;
            if(msgNumber <= numberMsgs){
              //Process the next message.

              //Get and save a unique identifier
              // for the message from the server
              // and validate the response.
              outputStream.println(
                            "UIDL " + msgNumber);
              uidl = validateOneLine();

              //Open an output file to save
              // the message.  Use the UIDL
              // as the file name.
              pathFileName = dataPath + uidl;
              DataOutputStream dataOut =
                          new DataOutputStream(
                            new FileOutputStream(
                                  pathFileName));

              //Send a RETR command to begin
              // the message retrieval process
              outputStream.println(
                            "RETR " + msgNumber);
              //Validate the response.
              String retrResponse =
                               validateOneLine();

              //Read the first line in the
              // message from the server.
              String msgLine =
                          inputStream.readLine();

              //Continue reading lines until
              // a "." is encountered as the
              // first char in a line.  That
              // signals the end of the msg.
              while(!(msgLine.equals("."))){
                //Write the line to the output
                // file and read the next
                // line.  Insert newline
                // characters when writing the
                // output to the file.
                dataOut.writeBytes(
                                 msgLine + "\n");
                msgLine = inputStream.readLine();

              }//end while
              //Close the output file.  The
              // message is now stored in a
              // local file with a file name
              // based on the unique ID
              // provided by the server.
              dataOut.close();

              //Show progress

              textArea.append(msgNumber + "\n");

              //Increment the message counter
              // in preparation for
              // processing the next message.
              msgCounter++;

              //Disable this statement to require
              // the user to press the button
              // for each new message.
              Toolkit.getDefaultToolkit().
                     getSystemEventQueue().
                       postEvent(new ActionEvent(
                              startButton,
                              ActionEvent.
                                ACTION_PERFORMED,
                              "Start/Next"));

            }//end if msgNumber <= numberMsgs
            else{//msgNumber > numberMsgs
              //No more messages. Disable the
              //Start/Next button.
              startButton.setEnabled(false);

              //Alert the user
              Toolkit.getDefaultToolkit().beep();
              Thread.currentThread().sleep(300);
              Toolkit.getDefaultToolkit().beep();
              Thread.currentThread().sleep(300);
              Toolkit.getDefaultToolkit().beep();
            }//end else
          }//end try
          catch(Exception ex){
                         ex.printStackTrace();}
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

    //Configure the GUI by placing the various
    // components on it, setting the size and
    // making it visible.
    add(startButton);
    add(textArea);
    textArea.setText("");
    setLayout(new FlowLayout());

    setTitle("Copyright 2004, R.G.Baldwin");
    setBounds(274,0,400,400);
    //Make the GUI visible.
    setVisible(true);
  }//end constructor
  //===========================================//

  //Validate a one-line response.
  //The purpose of this method is to confirm that
  // the server returned +OK and not -ERR to the
  // previous command.
  //If +OK, the method returns the string
  // returned by the server.
  //If -ERR, the method displays the string
  // returned by the server and terminates the
  // session.
  private String validateOneLine(){
    try{
      String response = inputStream.readLine();
      if(response.startsWith("+OK")){
        return response;
      }else{
        System.out.println(response);
        //Terminate the session.
        outputStream.println("QUIT");
        socket.close();
        System.out.println(
                       "Premature QUIT on -ERR");
        System.exit(0);
      }//end else
    }catch(IOException e){
      System.out.println("\n" + e);}
    //The following return statement is requied
    // to satisfy the compiler.
    return "Make compiler happy";
  }//end validateOneLine()
  //===========================================//

}//end class VirPro01a
//=============================================//
Listing 40

/*File VirPro01b.java
Copyright 2004, R.G.Baldwin
Rev 02/15/04

This is one of a pair of programs designed to be
used together, in conjunction with a good virus
scanner program to prevent messages with viruses
from contaminating an email inbox.

This program should be run after the program
named VirPro01a has been run, and a virus checker
has been used to confirm that all files produced
by that program are free of viruses, or that any
files containing viruses have been removed from
the system.

See comments at the beginning of VirPro01a.java
for a description of this pair of programs.

This program forwards clean email messages to a
secret email account.  On my system, using a
cable modem, about three to four seconds are
required to forward each message to the secret
email account.

This program is designed to be used with a POP3
email server.  For technical information on POP3,
see RFC 1725 at
http://www.cis.ohio-state.edu/htbin/rfc/rfc1725.
html

Usage:  Enter the following at the command line
(without the line break):
java VirPro01b pubServer userName password
secretServer smtpServer

where the command line parameters identify:
Your public email server
Your user name on the public server
Your password on the public server
Your private email account address
The SMTP server on which you are authorized to
  send email messages.

Tested using SDK 1.4.2 under WinXP
************************************************/
import sun.net.smtp.SmtpClient;
import java.net.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;

class VirPro01b extends Frame{
  //The following is the ID of the secret email
  // account provided as a command line parameter
  // when the program is started.
  String recipient;

  //The following is the local folder where
  // message files are stored awaiting virus
  // scanning and forwarding.  You may want to
  // change this to a different folder.
  String dataPath = "./Messages/";
  //The following is the local folder where the
  // messages are stored after they have been
  // scanned and forwarded to the secret email
  // account.  They are automatically moved to
  // this folder after being deleted from the
  // public email server. You will want to
  // manually empty this folder periodically.
  String archivePath = "./Archives/";

  //The following are working variables used by
  // the program for various purposes.
  BufferedReader inputStream;
  PrintWriter outputStream;
  Socket socket;
  String pathFileName;
  Vector msgToDelete = new Vector();

  public static void main(String[] args){
    if(args.length != 5){
      System.out.println("Usage: java VirPro01b "
                 + "pubServer userName password "
                 + "secretServer smtpServer");
      System.exit(0);
    }//end if

    new VirPro01b(args[0],args[1],args[2],
                                args[3],args[4]);
  }//end main
  //===========================================//

  //Constructor
  VirPro01b(final String server,
            final String userName,
            final String password,
            String secretServer,
            final String smtpServer){

    recipient = secretServer;

    //Register a window listener to service
    // the close button on the Frame.
    this.addWindowListener(
      new WindowAdapter(){
        public void windowClosing(WindowEvent e){
          System.exit(0);
        }//end windowClosing
      }//end WindowAdapter()
    );//end addWindowListener

    final Button startButton =
                        new Button("Start");
    final Button deleteButton = new Button(
                         "Delete Msg On Server");
    final TextArea textArea =
                             new TextArea(20,50);

    //Register an ActionListener on the
    // startButton.
    startButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          startButton.setEnabled(false);
          //Get a directory listing.  Make
          // certain that dataDir contains only
          // message files.
          File dataDir = new File(dataPath);
          String[] dirList = dataDir.list();

          //Now process the files in the
          // directory
          for(int msgCounter = 0;
                     msgCounter < dirList.length;
                                   msgCounter++){
            String fileName =
                             dirList[msgCounter];
            pathFileName = dataPath + fileName;

            //Forward the message to the secret
            // email account. You can tag the
            // subject with any string that you
            // want to pass as the third
            // parameter.  I will tag with the
            // message number as three digits.
            // That makes it easy to confirm that
            // all messages seccessfully reached
            // the secret email account.

            String strMsgNumber =
                  pathFileName.substring(
                  pathFileName.indexOf(" "),
                  pathFileName.lastIndexOf(" ")).
                  trim();
            int msgNumber = Integer.parseInt(
                                   strMsgNumber);
            String msgNumberStr;
            if(msgNumber < 10){
              msgNumberStr = "00" + msgNumber;
            }else if(msgNumber > 99){
              msgNumberStr = "" + msgNumber;
            }else{
              msgNumberStr = "0" + msgNumber;
            }//end else

            boolean okToDelete =
                       forwardEmailMsg(
                          recipient,
                          smtpServer,
                          "{"+ msgNumberStr +"}",
                          pathFileName);

            if(okToDelete){
              //Only those messages that were
              // successfully forwarded will be
              // deleted from the server and
              // moved to the archive folder.
              textArea.append("Forwarded " +
                            msgNumberStr + "\n");
              msgToDelete.add(pathFileName);
            }else{
              textArea.append("Failed " +
                            msgNumberStr + "\n");
            }//end else
          }//end for loop on directory length

          //Make it possible for the user to
          // delete all messages that were
          // successfully forwarded to the secret
          // email account from the public email
          // server.
          deleteButton.setEnabled(true);
          textArea.append("\nDo you want to "
             + "delete messages from server?\n");

          //Alert the user
          try{
            Toolkit.getDefaultToolkit().beep();
            Thread.currentThread().sleep(300);
            Toolkit.getDefaultToolkit().beep();
            Thread.currentThread().sleep(300);
            Toolkit.getDefaultToolkit().beep();
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

    //Register an action listener on the delete
    // button
    deleteButton.addActionListener(
      new ActionListener(){
        public void actionPerformed(
                                  ActionEvent e){
          deleteButton.setEnabled(false);
          textArea.append("\n");

          //Get connected to the email server
          int port = 110; //pop3 mail port
          try{
            //Get a socket, connected to the
            // specified server on the specified
            // port.
            socket = new Socket(server,port);

            //Get an input stream from the socket
            inputStream = new BufferedReader(
                     new InputStreamReader(
                       socket.getInputStream()));

            //Get an output stream to the socket.
            outputStream = new PrintWriter(
                     new OutputStreamWriter(
                       socket.getOutputStream()),
                                           true);

            //Display the msg received from the
            // server on the command line screen
            // immediately following connection.
            String connectMsg =
                               validateOneLine();
            System.out.println(
                           "Connected to server "
                                   + connectMsg);

            //The communication process is now in
            // the AUTHORIZATION state.  Send the
            // user name and password to the
            // server.
            //Commands are sent in plain text,
            // upper case to the server.  Some
            // commands require an argument
            // following the command, as is the
            // case with USER.
            //Send the command.
            outputStream.println("USER "
                                     + userName);
            //Get response and confirm that the
            // response was +OK and was not -ERR.
            String userResponse =
                               validateOneLine();
            //Display the response on the
            // command line screen.
            System.out.println("USER "
                                 + userResponse);
            //Send the password to the server
            outputStream.println("PASS "
                                     + password);
            //Validate the server's response as
            // +OK. Display the response in the
            // process.
            System.out.println("PASS "
                            + validateOneLine());
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch

          //Delete the collection of messages in
          // msgToDelete from the public email
          // server.  Also transfer the local
          // copies of the message files to the
          // archive folder.
          for(int cnt = 0;
                 cnt < msgToDelete.size();cnt++){
            pathFileName =
              (String)msgToDelete.elementAt(cnt);
            String strMsgNumber =
                pathFileName.substring(
                 pathFileName.indexOf(" "),
                  pathFileName.lastIndexOf(" ")).
                   trim();
            int msgNumber = Integer.parseInt(
                                   strMsgNumber);

            //Deletion of a message from the
            // server is accomplished by marking
            // the message for deletion while in
            // the TRANSACTION state.  The
            // message is actually deleted when
            // the client sends a QUIT command
            // to the server causing the server
            // to enter the UPDATE state.  If the
            // program aborts prematurely before
            // sending a QUIT command, marked
            // messages are not deleted from the
            // server.
            //Mark the message for deletion.
System.out.println(
            "Deletion is temporarily disabled.");
/*Deletion from the server temporarily disabled.
 *Do not enable this deletion code until you
 * understand exactly what you are doing.
            outputStream.println(
                            "DELE " + msgNumber);

            //Validate the response and display
            // it on the GUI.
            textArea.append(
                       "Msg: " + msgNumber + " "
                       + validateOneLine()+"\n");
            textArea.append(
                   "Marked:" + msgNumber + "\n");
*/

            //Now move the file that has been
            // processed and deleted from the
            // server to the archive folder
            // on the local disk.
            moveFile(pathFileName,archivePath);

          }//end for loop on msgToDelete.size()

          //Terminate the session with the
          // server causing the messages to
          // actually be deleted from the server.
          outputStream.println("QUIT");
          String quitResponse =
                               validateOneLine();
          //Display the response on the
          // command line screen.
          System.out.println(
                         "QUIT " + quitResponse);

          //Server is now in the UPDATE mode.
          // It will delete all files marked
          // with the DELE command earlier.
          //Close the socket
          try{
            socket.close();
          }catch(Exception ex){
            ex.printStackTrace();
          }//end catch

          textArea.append("\n\nMessages deleted "
                             + "from server.\n");
        }//end actionPerformed
      }//end ActionListener
    );//end addActionListener

    //Configure the GUI by placing the
    // various components on it, setting the size
    // and making it visible.
    add(startButton);
    add(deleteButton);
    deleteButton.setEnabled(false);
    add(textArea);
    textArea.setText("");
    setLayout(new FlowLayout());

    setTitle("Copyright 2004, R.G.Baldwin");
    setBounds(274,0,400,400);
    //Make the GUI visible.
    setVisible(true);
  }//end constructor
  //===========================================//

  //Validate a one-line response.
  //The purpose of this method is to confirm that
  // the server returned +OK and not -ERR to the
  // previous command.
  //If +OK, the method returns the string
  // returned by the server.
  //If -ERR, the method displays the string
  // returned by the server and terminates the
  // session.
  private String validateOneLine(){
    try{
      String response = inputStream.readLine();
      if(response.startsWith("+OK")){
        return response;
      }else{
        System.out.println(response);
        //Terminate the session.
        outputStream.println("QUIT");
        socket.close();
        System.out.println(
                       "Premature QUIT on -ERR");
        System.exit(0);
      }//end else
    }catch(IOException e){
      System.out.println("\n" + e);
    }//end catch
    //The following return statement is requied
    // to satisfy the compiler.
    return "Make compiler happy";
  }//end validateOneLine()
  //===========================================//

  private boolean forwardEmailMsg(
                            String recipient,
                            String smtpServer,
                            String tag,
                            String pathFileName){

      StringBuffer message = new StringBuffer(
                             "No message found");

      try{
        //Pass a string containing the name of
        // the smtp server as a parameter to the
        // following constructor.
        SmtpClient smtp =
                      new SmtpClient(smtpServer);

        //Pass a valid email address to the
        // from() method.
        smtp.from(recipient);

        //Pass the email address of the recipient
        // to the to() method.
        smtp.to(recipient);

        //Get an output stream for the message
        PrintStream msg = smtp.startMessage();

        //Write the message into the output stream
        message = new StringBuffer(readLines(
                    pathFileName,null,null));

        //Insert tag in subject line
        message = message.insert(message.indexOf(
                             "Subject: ")+9,tag);
        msg.println(new String(message));
        //Close the stream and send the message
        smtp.closeServer();

        return true;
      }catch( Exception e ){
        System.out.println("\n" + e);
        System.out.println("Forwarding email");
        Toolkit.getDefaultToolkit().beep();
        try{
          Thread.currentThread().sleep(300);
        }catch(Exception ex){
          System.out.println(ex);
        }//end catch
        Toolkit.getDefaultToolkit().beep();
        return false;
      }//end catch

  }//end forwardEmailMsg
  //===========================================//

  //Method moves a file from its current location
  // specified by pathFileName to a new location
  // specified by archivePath.
  private void moveFile(String pathFileName,
                             String archivePath){
    String fileName = pathFileName.substring(
              pathFileName.lastIndexOf('/') + 1);
    String archivePathFileName =
                          archivePath + fileName;

    boolean moved =
           new File(pathFileName).renameTo(
             new File(archivePathFileName));

    if(!moved)System.out.println(
      "Unable to move " + new File(pathFileName)
      + "\nto " + new File(archivePathFileName));
  }//end moveFile method
  //===========================================//

  //This method reads and saves lines of data
  // from a file starting with the line that
  // startsWith firstLine and ending with the
  // line that startsWith lastLine.  If lastLine
  // is null, data is saved to the end of the
  // file. If firstLine is null, data is saved
  // beginning with the first line in the file.
  // The lines of data from the file are saved by
  // concatenating them into a single string with
  // a newline inserted into the string at the
  // end of each line.
  //The name and path to the file is given by
  // pathFileName.
  private String readLines(String pathFileName,
               String firstLine,String lastLine){
    StringBuffer strBuf = new StringBuffer();
    try{
      BufferedReader inDataMsg
        = new BufferedReader(new FileReader(
                                  pathFileName));

      String data;
      boolean isSave = false;
      while((data = inDataMsg.readLine())
                                        != null){

        if(((firstLine == null) ||
                 (data.startsWith(firstLine))) &&
                              (isSave == false)){
          isSave = true;
        }//end if

        if(isSave){
          strBuf.append(data + "\n");
        }//end if

        if((lastLine != null) &&
                    (data.startsWith(lastLine))){
          break;//no need to read any more
        }//end if

      }//end while loop
      inDataMsg.close();//Close file
    }catch(Exception e){e.printStackTrace();}
    return new String(strBuf);
  }//end readLines
  //===========================================//

}//end class VirPro01b
//=============================================//
Listing 41