FTP CLIENT SERVER COMMUNICATION

This is an implementation of FTP Client Server interaction written in JAVA. It is a widely used protocol for remote file access.

Most of the Programmer need to work on remote Client Network.And so they will be needing to access remote files. File Transfer Protocol will help them to access remote files.This snippet can help them understand how its implemented in JAVA.   

//FtpClient.java

import java.net.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.*;
class FtpClient extends JFrame implements ActionListener
{
 String fn,filenm;
 String fc;
 String dirn="c:/FTP CLIENT DIRECTORY";
 JPanel pnl;
 JLabel lbltle,lblud;
 Font fnt;
 JTextField txtfn;
 JButton btnu,btnd;
 Socket s;
 InputStreamReader in;
 OutputStream out;
 BufferedReader br;
 PrintWriter pw;
 public FtpClient()
 {
  super("FTP CLIENT");

  pnl=new JPanel(null);

  fnt=new Font("Times New Roman",Font.BOLD,25);

  lbltle=new JLabel("FTP CLIENT");
  lbltle.setFont(fnt);
  lbltle.setBounds(225,35,200,30);
  pnl.add(lbltle);

  lblud=new JLabel("ENTER  FILE-NAME :");
  lblud.setBounds(100,100,150,35);
  pnl.add(lblud);

  txtfn=new JTextField();
  txtfn.setBounds(300,100,200,25);
  pnl.add(txtfn);

  btnu=new JButton("UPLOAD");
  btnu.setBounds(150,200,120,35);
  pnl.add(btnu);


  btnd=new JButton("DOWNLOAD");
  btnd.setBounds(320,200,120,35);

  pnl.add(btnd);

  btnu.addActionListener(this);
  btnd.addActionListener(this);
  getContentPane().add(pnl);

  try
  {
   s=new Socket("localhost",100);
   br=new BufferedReader(new InputStreamReader(s.getInputStream()));
   pw=new PrintWriter(s.getOutputStream(),true);
   out=s.getOutputStream();
  }
  catch(Exception e)
  {
   System.out.println("ExCEPTION :"+e.getMessage());
  }
 }
 public void actionPerformed(ActionEvent e)
 {
  if(e.getSource()==btnu)
  {
   try
   {
    filenm=txtfn.getText();
    pw.println(filenm);
    FileInputStream  fis=new FileInputStream(filenm);
    byte[] buffer=new byte[1024];
    int bytes=0;

    while((bytes=fis.read(buffer))!=-1)
    {
     out.write(buffer,0,bytes);
    }
    fis.close();
   }
   catch(Exception exx)
   {
    System.out.println(exx.getMessage());
   }
  }

  if(e.getSource()==btnd)
  {
   try
   {
    File dir=new File(dirn);
    if(!dir.exists())
    {
     dir.mkdir();
    }
    else{}
    boolean done=true;
    filenm=txtfn.getText();
    fn=new String("#"+filenm+"#");
    //System.out.println(filenm);
    pw.println(fn);
    File f=new File(dir,filenm);
    FileOutputStream fos=new FileOutputStream(f);
    DataOutputStream dops=new DataOutputStream(fos);
    while(done)
    {
     fc=br.readLine();
     if(fc==null)
     {
      done=false;
     }
     else
     {
      dops.writeChars(fc);
      //  System.out.println(fc);

     }
    }
    fos.close();
   }

   catch(Exception exx)
   {}

  }
 }
 public static void main(String args[])
 {
  FtpClient ftpc=new FtpClient();
  ftpc.setSize(600,300);
  ftpc.show();
 }
}



//FtpServer.java
import java.io.*;
import java.net.*;

public class FtpServer
{
 public static void main(String [] args)
 {
  int i=1;

  System.out.println("******************************************************
    **************************");
    System.out.println("******************************   FTP 
      SERVER
      ***********************************");

      System.out.println("******************************************************
        **************************");
        System.out.println("Server Started...");
        System.out.println("Waiting for connections...");
        System.out.println("
          ");
          try
          {

           ServerSocket s = new ServerSocket(100);
           for(;;)
           {
            Socket incoming = s.accept();
            System.out.println("New Client Connected with id " 
              + i
              +" from "+incoming.getInetAddress().getHostName()+"..." );
            Thread t = new ThreadedServer(incoming,i);
            i++;
            t.start();
           }
          }
          catch(Exception e)
          {
           System.out.println("Error: " + e);
          }
 }
}

class ThreadedServer extends Thread
{
 int n;
 String c,fn,fc;
 String filenm;
 Socket incoming;
 int counter;
 String dirn="c:/FTP SERVER DIRECTORY";
 public ThreadedServer(Socket i,int c)
 {
  incoming=i;
  counter=c;
 }

 public void run()
 {
  try
  {

   BufferedReader in =new BufferedReader(new
     InputStreamReader(incoming.getInputStream()));
   PrintWriter out = new
     PrintWriter(incoming.getOutputStream(), true);
   OutputStream output=incoming.getOutputStream();
   fn=in.readLine();
   c=fn.substring(0,1);

   if(c.equals("#"))
   {
    n=fn.lastIndexOf("#");
    filenm=fn.substring(1,n);
    FileInputStream fis=null;
    boolean filexists=true;
    System.out.println("Request to download file "+filenm+"
      recieved from "+incoming.getInetAddress().getHostName()+"...");
      try
    {
       fis=new FileInputStream(filenm);
    }
    catch(FileNotFoundException exc)
    {
     filexists=false;
     System.out.println("FileNotFoundException:
      "+exc.getMessage());
    }
    if(filexists)
    {
     sendBytes(fis, output) ;
     fis.close();
    }
   }
   else
   {
    try
    {
     boolean done=true;
     System.out.println("Request to upload file " +fn+"
       recieved from "+incoming.getInetAddress().getHostName()+"...");

       File dir=new File(dirn);
     if(!dir.exists())
     {
      dir.mkdir();
     }
     else
     {}
     File f=new File(dir,fn);
     FileOutputStream fos=new FileOutputStream(f);
     DataOutputStream dops=new DataOutputStream(fos);

     while(done)
     {
      fc=in.readLine();
      if(fc==null)
      {
       done=false;
      }
      else
      {
       dops.writeChars(fc);
       // System.out.println(fc);

      }
     }
     fos.close();
    }
    catch(Exception ecc)
    {
     System.out.println(ecc.getMessage());
    }
   }
   incoming.close();
  }
  catch(Exception e)
  {
   System.out.println("Error: " + e);
  }
 }
 private static void sendBytes(FileInputStream f,OutputStream op)
   throws Exception
   {
  byte[] buffer=new byte[1024];
  int bytes=0;

  while((bytes=f.read(buffer))!=-1)
  {
   op.write(buffer,0,bytes);
  }
   }
}