java UDP传输文件

Question

   我最近在做一个课程设计，里面设计到用socket进行传输文件，我用的udp传输文件，这样要快一点，但是没想到当我传输的文件大于20M的时候就开始出问题了，大家有好点的用udp传输文件的例子吗？最好是能把思路说说，呵呵！ 
   最近搞多线程，脑壳都搞大了！

Answer 1

import java.net.*;
import javax.swing.*; 
import java.awt.event.*;
class 主机1Frame extends JFrame implements Runnable,ActionListener
{  JTextField out_message=new JTextField("发送数据到主机2：");
   JTextArea in_message=new JTextArea(); 
   JButton b=new JButton("发送数据包到主机2");
   主机1Frame()
   {  super("我是主机1");
      setSize(200,200);setVisible(true);
      b.addActionListener(this);
      add(out_message,"South");add(in_message,"Center");add(b,"North");
      Thread thread=new Thread(this);
      thread.start();//线程负责接收数据包
   }
   public void actionPerformed(ActionEvent event) //点击按扭发送数据包
   {  byte buffer[]=out_message.getText().trim().getBytes();
      try{  InetAddress address=InetAddress.getByName("127.0.0.1");
DatagramPacket data_pack=
new DatagramPacket(buffer,buffer.length, address,888);
            DatagramSocket mail_data=new DatagramSocket();
            in_message.append("数据报目标主机地址:"+data_pack.getAddress()+"\n");
            in_message.append("数据报目标端口是:"+data_pack.getPort()+"\n");
            in_message.append("数据报长度:"+data_pack.getLength()+"\n");
            mail_data.send(data_pack);
          }
      catch(Exception e){}     
   } 
   public void run() //接收数据包
   {  DatagramPacket pack=null;
      DatagramSocket mail_data=null;
      byte data[]=new byte[8192];
      try{  pack=new DatagramPacket(data,data.length);
            mail_data=new DatagramSocket(666);
         }
      catch(Exception e){} 
      while(true)   
         {  if(mail_data==null) break;
            else
               try{  mail_data.receive(pack); 
                     int length=pack.getLength();
                     InetAddress adress=pack.getAddress();
                     int port=pack.getPort();
                     String message=new String(pack.getData(),0,length);
                     in_message.append("收到数据长度："+length+"\n");
                     in_message.append("收到数据来自："+adress+"端口："+port+"\n");
                     in_message.append("收到数据是："+message+"\n");
                  }
               catch(Exception e){}
         } 
   }
}
public class 主机1
{  public static void main(String args[])
   {  主机1Frame 主机1win=new 主机1Frame();
      主机1win.validate();
   }
}import java.net.*;
import javax.swing.*; 
import java.awt.event.*;
class 主机2Frame extends JFrame implements Runnable,ActionListener
{  JTextField out_message=new JTextField("发送数据到主机1：");
   JTextArea in_message=new JTextArea(); 
   JButton b=new JButton("发送数据包到主机1");
   主机2Frame()
   {  super("我是主机2"); 
      setSize(200,200);setVisible(true);
      b.addActionListener(this);
      add(out_message,"South");add(in_message,"Center");add(b,"North");
      Thread thread=new Thread(this);
      thread.start();//线程负责接收数据包
   }
   public void actionPerformed(ActionEvent event)
   {  byte buffer[]=out_message.getText().trim().getBytes();
      try{  InetAddress address=InetAddress.getByName("127.0.0.1");
DatagramPacket data_pack=
new DatagramPacket(buffer,buffer.length, address,666);
            DatagramSocket mail_data=new DatagramSocket();
            in_message.append("数据报目标主机地址:"+data_pack.getAddress()+"\n");
            in_message.append("数据报目标端口是:"+data_pack.getPort()+"\n");
            in_message.append("数据报长度:"+data_pack.getLength()+"\n");
            mail_data.send(data_pack);
         }
       catch(Exception e){}   
   } 
   public void run()
   {  DatagramSocket mail_data=null;
      byte data[]=new byte[8192];
      DatagramPacket pack=null;
     try{
           pack=new DatagramPacket(data,data.length);
           mail_data=new DatagramSocket(888);
         }
     catch(Exception e){} 
     while(true)   
       {  if(mail_data==null) break;
          else
           try{  mail_data.receive(pack); 
                 int length=pack.getLength();
                InetAddress adress=pack.getAddress();
                int port=pack.getPort();
   String message=new String(pack.getData(),0,length);
                in_message.append("收到数据长度："+length+"\n");
                in_message.append("收到数据来自："+adress+"端口："+port+"\n");
                in_message.append("收到数据是："+message+"\n");
              }
           catch(Exception e){}
       }
   }
}
public class 主机2
{   public static void main(String args[])
   {  主机2Frame 主机2win=new 主机2Frame();
       主机2win.validate();
   }
}