如何在Java項目中使用UDP協(xié)議發(fā)送消息

package lesson03;

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

/**
 * 發(fā)送端
 */
public class UdpClientDemo1 {

  public static void main(String[] args) throws Exception {

    //1、建立一個 Socket
    DatagramSocket socket = new DatagramSocket();

    /**
     * 2、建個包
     */

    //需要發(fā)送的消息
    String msg = "你好啊，服務(wù)器！";

    //發(fā)送地址
    InetAddress localhost = InetAddress.getByName("localhost"); //主機(jī)
    //發(fā)送端口
    int port = 9090;

    /**
     * 五個參數(shù)：
     * @param  buf  msg.getBytes()：需要發(fā)送的數(shù)據(jù)包
     * @param  offset  0：數(shù)據(jù)偏移量
     * @param  length  msg.getBytes().length：數(shù)據(jù)長度
     * @param  address  localhost：目標(biāo)地址
     * @param  port  port：目標(biāo)端口
     */
    DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);

    //3、發(fā)送包
    socket.send(packet);

    //4、關(guān)閉流
    socket.close();
  }

}

package lesson03;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

/**
 * 接收端
 */
public class UdpServerDemo1 {

  public static void main(String[] args) throws Exception {

    //開放端口
    DatagramSocket socket = new DatagramSocket(9090);

    //接收數(shù)據(jù)包
    byte[] buffer = new byte[1024];
    DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

    //接收
    socket.receive(packet); //阻塞接收

    //輸出數(shù)據(jù)包地址
    System.out.println(packet.getAddress().getHostAddress());
    /**
     * 輸出數(shù)據(jù)包數(shù)據(jù)
     * packet：Data 類型
     * 通過構(gòu)造器轉(zhuǎn)成 String 類型：new String();
     */
    System.out.println(new String(packet.getData(), 0, packet.getLength()));

    //關(guān)閉連接
    socket.close();

  }

}