UDP Client

import java.net.*;
class Client
{
    Client()
    {
        try
        {
            //服务器IP地址
            InetAddress    ip     = InetAddress.getByName("127.0.0.1");
            //代表具体应用程序
            int            port   = 9000;
            //i开辟空间，用来形成数据包
            byte           buf[]  = new byte[200];
            //备用数据包，等着接收对方传递过来的数据
            DatagramPacket rDP    = new DatagramPacket(buf,200);
            //接收和发送引擎
            DatagramSocket socket = new DatagramSocket();
            
            for(int i=0;i<10;i++)
            {
                Thread.sleep(1000);
                String info = "问世间****为何物";
                //把我们的字符串形成packet
                DatagramPacket sendPacket=StringToPacket(ip,port,info);
                //发送
                socket.send(sendPacket);
                //接收
                socket.receive(rDP);
                //把接收到的数据转换为字符串
                String str = PacketToString(rDP);
                System.out.println("from Server:"+str);
            }
        }
        catch(Exception e)
        {
            System.out.println(e.getMessage());
            e.printStackTrace();
        }
    }
    
    public static void main(String s[])
    {
        Client client = new Client();
    }
    
    //把字符串转换为数据包
    DatagramPacket StringToPacket(InetAddress ip,int port,String message)
    {
        //String ----->byte[] + ip  ＋ｐｏｒｔ　　＝　ＤａｔａｇｒａｍＰａｃｋｅｔ
        //查看字符串有多大
        int    length = message.length();
        //根据大小开辟空间
        byte   buf[]  = new byte[length];
        //把字符串的内容导入数据包
        buf           = message.getBytes();
        //把byte[]+ip+port------->数据包
        DatagramPacket  dp = new DatagramPacket(buf,0,buf.length,ip,port);
        return dp; 
    }
    
    //DatagramPacket----->byte[]-------->String
    //把数据包转换为字符串
    String PacketToString(DatagramPacket dp)
    {
        //查看数据包大小
        int  length = dp.getLength();
        //根据大小开辟空间
        byte buf[]  = new byte[length];
        //把数据包的内容转入字符数组中
        buf         = dp.getData();
        //把字符数组的内容转换为字符串
        String str  = new String(buf,0,length);
        return str;
    }
}