UDP消息发送

发短信：不用连接，需要知道对方的地址

发送消息

package Demo02;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdoServerDemo01 {
    public static void main(String[] args) throws IOException {
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接受数据包
        byte[] buffer=new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        socket.receive(packet);//阻塞接受
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));

        //关闭连接
        socket.close();

    }
}

package Demo02;

import java.io.IOException;
import java.net.*;

public class UdpClientDemo01 {
    public static void main(String[] args) throws SocketException {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();

        //2.建个包
        String msg="你好";
        //发送给谁
        InetAddress localhost= null;
        try {
            localhost = InetAddress.getLocalHost();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        int port=9090;

        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);
        //3.发送包
        try {
            socket.send(packet);
        } catch (IOException e) {
            e.printStackTrace();
        }
        //关闭流
        socket.close();
    }
}