portSocket.close();
	   }//end of port transfer

        return dataSocket;     // return the dataSocket
    }


    /** open a FTP connection to host <i>host</i>. */
    public void openServer(String host) throws IOException, UnknownHostException {
        int port = FTP_PORT;
        if (serverSocket != null)
            closeServer(); 
        serverSocket = new Socket(host, FTP_PORT);    
        serverOutput = new PrintWriter(new BufferedOutputStream(serverSocket.getOutputStream()),true);
        serverInput = new BufferedInputStream(serverSocket.getInputStream());
    }

    /** open a FTP connection to host <i>host</i> on port <i>port</i>. */
    public void openServer(String host, int port) throws IOException, UnknownHostException {
        if (serverSocket != null)
            closeServer();
        serverSocket = new Socket(host, port);
        //serverSocket.setSoLinger(true,30000);
        serverOutput = new PrintWriter(new BufferedOutputStream(serverSocket.getOutputStream()),
                                       true);
        serverInput = new BufferedInputStream(serverSocket.getInputStream());

        if (readReply() == FTP_ERROR)
            throw new FtpConnectException("Welcome message");
    }


    /** 
     * login user to a host with username <i>user</i> and password 
     * <i>password</i> 
     */
    public void login(String user, String password) throws IOException {
       
        if (!serverIsOpen())
            throw new FtpLoginException("Error: not connected to host.\n");
        this.user = user;
        this.password = password;
        if (issueCommand("USER " + user) == FTP_ERROR)
            throw new FtpLoginException("Error: User not found.\n");
        if (password != null && issueCommand("PASS " + password) == FTP_ERROR)
            throw new FtpLoginException("Error: Wrong Password.\n");       
    }

    /** 
     * login user to a host with username <i>user</i> and no password 
     * such as HP server which uses the form "<username>/<password>,user.<group>
     */
    public void login(String user) throws IOException {

        if (!serverIsOpen())
            throw new FtpLoginException("not connected to host");
        this.user = user;        
        if (issueCommand("USER " + user) == FTP_ERROR)
            throw new FtpLoginException("Error: Invalid Username.\n");                 
    }

    /** GET a file from the FTP server in Ascii mode*/
    public BufferedReader getAscii(String filename) throws IOException {     
        Socket  s = null;
        try {
            s = openDataConnection("RETR " + filename);
        } catch (FileNotFoundException fileException) {fileException.printStackTrace();}
        return new BufferedReader( new InputStreamReader(s.getInputStream()));          
    }

    /** GET a file from the FTP server in Binary mode*/
    public BufferedInputStream getBinary(String filename) throws IOException {     
        Socket  s = null;
        try {
            s = openDataConnection("RETR " + filename);
        } catch (FileNotFoundException fileException) {fileException.printStackTrace();}
        return new BufferedInputStream(s.getInputStream());          
    }


    /** PUT a file to the FTP server in Ascii mode*/
    public BufferedWriter putAscii(String filename) throws IOException {
        Socket s = openDataConnection("STOR " + filename);
        return new BufferedWriter(new OutputStreamWriter(s.getOutputStream()),4096);
    }
     
    /** PUT a file to the FTP server in Binary mode*/
    public BufferedOutputStream putBinary(String filename) throws IOException {
        Socket s = openDataConnection("STOR " + filename);
        return new BufferedOutputStream(s.getOutputStream());
    }

    /** APPEND (with create) to a file to the FTP server in Ascii mode*/
    public BufferedWriter appendAscii(String filename) throws IOException {
        Socket s = openDataConnection("APPE " + filename);
        return new BufferedWriter(new OutputStreamWriter(s.getOutputStream()),4096);
    }

    /** APPEND (with create) to a file to the FTP server in Binary mode*/
    public BufferedOutputStream appendBinary(String filename) throws IOException {
        Socket s = openDataConnection("APPE " + filename);
        return new BufferedOutputStream(s.getOutputStream());
    }



   /** NLIST files on a remote FTP server */
    public BufferedReader nlist() throws IOException {
        Socket s = openDataConnection("NLST");        
        return new BufferedReader( new InputStreamReader(s.getInputStream()));
    }

    /** LIST files on a remote FTP server */
    public BufferedReader list() throws IOException {
        Socket s = openDataConnection("LIST");        
        return new BufferedReader( new InputStreamReader(s.getInputStream()));
    }

    /** CD to a specific directory on a remote FTP server */
    public void cd(String remoteDirectory) throws IOException {
        issueCommandCheck("CWD " + remoteDirectory);
    }

    /** Rename a file on the remote server */
    public void rename(String oldFile, String newFile) throws IOException {
         issueCommandCheck("RNFR " + oldFile);
         issueCommandCheck("RNTO " + newFile);
    }
      
    /** Site Command */ 
    public void site(String params) throws IOException {
         issueCommandCheck("SITE "+ params);
    }            
	
    /** Set transfer type to 'I' */
    public void binary() throws IOException {
        issueCommandCheck("TYPE I");
        binaryMode = true;
    }

    /** Set transfer type to 'A' */
    public void ascii() throws IOException {
        issueCommandCheck("TYPE A");
        binaryMode = false;
    }

    /** Send Abort command */
    public void abort() throws IOException {
        issueCommandCheck("ABOR");
    }

    /** Go up one directory on remots system */
    public void cdup() throws IOException {
        issueCommandCheck("CDUP");
    }

    /** Create a directory on the remote system */
    public void mkdir(String s) throws IOException {
        issueCommandCheck("MKD " + s);
    }

    /** Delete the specified directory from the ftp file system */
    public void rmdir(String s) throws IOException {
        issueCommandCheck("RMD " + s);
    }

    /** Delete the file s from the ftp file system */
    public void delete(String s) throws IOException {
        issueCommandCheck("DELE " + s);
    }

    /** Get the name of the present working directory on the ftp file system */
    public void pwd() throws IOException {
        issueCommandCheck("PWD");
    }
    
    /** Retrieve the system type from the remote server */
    public void syst() throws IOException {
        issueCommandCheck("SYST");
    }


    /** New FTP client connected to host <i>host</i>. */
    public FtpClient(String host) throws IOException {      
        openServer(host, FTP_PORT);      
    }

    /** New FTP client connected to host <i>host</i>, port <i>port</i>. */
    public FtpClient(String host, int port) throws IOException {
        openServer(host, port);
    }
    
    /** Method to demonstrate use of FtpClient class */

    public static void main (String args []) throws IOException{
      System.out.println("Demo of FtpClient class.\n");

      // standard login procedures, must be done on all ftp servers 

      FtpClient f = new FtpClient("ftp.sun.com");

      System.out.print(f.getResponseString());

      f.login("anonymous","me@abc.com");
      System.out.print(f.getResponseString());
                        
      f.pwd(); 
      System.out.println(f.command);                  
      System.out.print(f.getResponseString());

      f.setPassive(true);

      // here's how you can do a listing

      System.out.println("\nDemo of nlist() function");

      f.ascii();  // set client to ascii mode to get text listing   
      System.out.println(f.command);              
      System.out.print(f.getResponseString());
          
      BufferedReader t = f.nlist();     // f.list gives a few more details
      System.out.println(f.command);
      System.out.print(f.getResponseString());  
      while( true ) {
         String stringBuffer = t.readLine();
         if( stringBuffer == null ) break;
         else System.out.println(stringBuffer);               
      }
      t.close();
      System.out.print(f.getResponseString());  
      // here's how to get a file using the getAscii() function.  The getBinary() function is similar in use  
      
      System.out.println("\nDemo of getAscii() function");

      f.ascii();           //  set transfer mode to ASCII, it has to be done by the user.
      System.out.println(f.command);
      System.out.print(f.getResponseString());  
      BufferedReader bufGet = f.getAscii("welcome.msg");
      System.out.println(f.command);      
      System.out.print(f.getResponseString());      
      PrintWriter pOut = new PrintWriter(new BufferedWriter(new FileWriter("welcome.msg")));
      int i;                                
      char c[] = new char[4096];
      while ((i = bufGet.read(c)) != -1) 
        pOut.write(c,0,i);                                                   
      bufGet.close();
      pOut.close();            
        
      System.out.print(f.getResponseString());     

      
      // here's how to APPEND an ASCII file using the appendAscii() function.  The appendBinary() function
      // is similar in use.  I am leaving this code commented out because you can't send files to the 
      // sun ftp site but you can try this on another ftp server
    
	/*
      System.out.println("\nDemo of appendAscii() function");
      BufferedWriter bufAppe;
      String localFile = "file name goes here"; 
      f.ascii();
      System.out.println(f.command);
      try {
      bufAppe = f.appendAscii(localFile);
      System.out.println(f.command);
      System.out.print(f.getResponseString());     
      
	FileReader fIn = new FileReader(localFile);            
      BufferedReader bufIn = new BufferedReader(fIn);
      int k;
      char b[] = new char[1024];
      while ((k = bufIn.read(b)) != -1) 
        bufAppe.write(b,0,k);                                  
      bufIn.close();
      bufAppe.flush();
      bufAppe.close();                 
      }catch(Exception appendErr) {
         System.out.println(appendErr.toString());//printStackTrace();
         
        }

      System.out.print(f.getResponseString()); 
	


      // here's how to send a binary file using the putBianary() function.  The putAscii() function
      // is similar in use.  I am leaving this code commented out because you can't send files to the 
      // sun ftp site but you can try this on another ftp server
    

      System.out.println("\nDemo of putBinary() function");
 
      String localFile = "file name goes here"; 
      f.binary();
      System.out.println(f.command);
      BufferedOutputStream bufPut = f.putBinary(localFile);
      System.out.println(f.command);
      System.out.print(f.getResponseString());     
      BufferedInputStream bufIn = new BufferedInputStream(new FileInputStream(localFile));
      int j;
      byte b[] = new byte[1024];
      while ((j = bufIn.read(b)) != -1) 
        bufPut.write(b,0,j);                                  
      bufIn.close();
      bufPut.flush();
      bufPut.close();                 

      System.out.print(f.getResponseString()); 
*/
      // close the connection

      f.closeServer();
      System.out.println(f.command);
      System.out.print(f.getResponseString());
    }


}

class FtpLoginException extends FtpProtocolException {
    FtpLoginException(String s) {
        super(s);
    }
}
class FtpConnectException extends FtpProtocolException {
    FtpConnectException(String s) {
        super(s);
    }
}

class FtpProtocolException extends IOException {
    FtpProtocolException(String s) {
        super(s);     
    }
}