package udp;
import java.net.* ;
public class UdpTest
{
      public  static void main(String []args)
      {
        if (args.length > 0)
          runServer();
          else
            runClient() ;
      }
   static   public void runServer()   //服务器端
      {
        try
        {
          DatagramSocket ss = new DatagramSocket(6666);  //创建数据包套接字
          byte date[]=new byte[100];
          while(true)
          {
          DatagramPacket dp=new DatagramPacket (date,100) ;   //创建数据包
          ss.receive(dp);
          System.out.println(new String(date,0,dp.getLength())); //将受到的数据写入
          String str="welcome you";
          DatagramPacket dp1=new DatagramPacket(str.getBytes(),str.length(),dp.getAddress(),dp.getPort());
          ss.send(dp1);
          }

        }
        catch(Exception e)
        {
          e.printStackTrace();
        }

      }
   static   public void runClient()   //客户端
      {
     try{
           DatagramSocket ss = new DatagramSocket();  //创建数据包套接字
           String str="hello i am zhangsan !";
           DatagramPacket p=new DatagramPacket(str.getBytes(),str.length(),InetAddress.getByName("LocalHost"),6666);
           ss.send(p);
           byte ch[]=new byte[100];
           DatagramPacket p1=new DatagramPacket(ch,100) ;
           ss.receive(p1);
           System.out.println(new String(ch,0,p1.getLength()));
           ss.close();
        }
        catch(Exception e)
        {
          e.printStackTrace();
        }

      }

 

}