c14_7.java

这是java网络编程的8个比较典型的实例

//UDP 服务器端程序：
 import java.io.*;
 import java.net.*;
 import java.util.*;
 class  UDPServerThread extends Thread{ //启动服务器线程的主程序
    private DatagramPacket packet;
    private DatagramSocket socket;
    static final int sport=1777;
    UDPServerThread(){
     try{
        // 将socket连接到本机的一个可用的端口上
         socket=new DatagramSocket(sport);
         System.out.println("Listening on port:"+socket.getLocalPort());
        }
catch(Exception e){  System.out.println("Error："+e); }
   }

   public void run()
{  //线程的主要操作
     if(socket==null)return;
     while(true){
       try{
         InetAddress address;
         int cport;
         byte[] buf=new byte[1000];
         String s="Your packet is received";
         packet=new DatagramPacket(buf,buf.length); //生成一个接收数据报
         socket.receive(packet);    //接收数据报
         String s1=new String(packet.getData());
         System.out.println("Received from client: "+s1);    //打印数据报的内容
         address=packet.getAddress();
         cport=packet.getPort();    //获得数据报的源地址与端口
         s.getBytes(0,s.length(),buf,0);
         packet=new DatagramPacket(buf,buf.length,address,cport);  //生成发送的数据报
         socket.send(packet);     // 发送数据报给客户
        }
       catch(Exception e){   System.out.println("Error："+e);    }
      }
    }
    protected void finalize(){
      if(socket!=null){
        socket.close(); //关闭socket
        System.out.println("Socket Closed.");
      }
    }
  }
  public class c14_7{   
    public static void main(String[] args){
    UDPServerThread server=new UDPServerThread();
    server.start();}
  }