网络编程03：UDP消息发送

UDP不需要连接服务器，只管发送即可
我们这里为了方便，模拟了一个接收端，接收端也可发送消息

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

//UDP实际上不需要连接服务器，只管发送消息就行
//在这里，我们为了方便，写一个接收端
public class UdpClientDemo01 {
    public static void main(String[] args) throws IOException {
        //1.建立一个socket
        DatagramSocket socket = new DatagramSocket();
        //2.建一个包
        String msg="你好，我是给bug带个赞";
        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port=9090;
        //数据，数据的长度起始，要发送给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);
        //3.发送包
        socket.send(packet);

        //4.关闭,包不需要关闭
        socket.close();

    }
}

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

public class UdpReceiveDemo01 {
    public static void main(String[] args) throws IOException {

        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer =new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        socket.receive(packet);//阻塞接收

        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0, packet.getLength()));

        socket.close();
    }
}