Java实现：文件传输

//代码经过编译，运行，证明可以运行
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
import java.net.*;
import javax.swing.filechooser.FileFilter;
public class Ftp extends JLabel
{
 private JButton openButton;
 private JButton saveButton;
 JFileChooser fc;
 String fileName;
 int result;
 Ftp()
 {
  setLayout(new GridLayout());
  JButton openButton = new JButton("Open");
  openButton.addActionListener(new openFile());
  JButton saveButton = new JButton("Save");
  saveButton.addActionListener(new saveFile());
  add(openButton);
  add(saveButton);
 }
 class openFile implements ActionListener
 {
  public void actionPerformed(ActionEvent e)
  {
   fc = new JFileChooser();
   result = fc.showOpenDialog(Ftp.this);
   File file = fc.getSelectedFile();
   if(file != null && result == JFileChooser.APPROVE_OPTION)
   {
    fileName = file.getAbsolutePath();
    System.out.println("选择你要打开的文件：" + fileName);
    try
    {
     File file1 = new File(fileName);
     FileInputStream fos = new FileInputStream(file1);
     ServerSocket ss = new ServerSocket(2048);
     Socket client = ss.accept();
     OutputStream netOut = client.getOutputStream();
     OutputStream doc = new DataOutputStream(new BufferedOutputStream(netOut));
     byte[] buf = new byte[2048];
     int num = fos.read(buf);
     while(num != (-1))
     {
&nb