一个UDP通信案例

一个UDP通信案例

需要的依赖

<dependency>
	<groupId>cn.hutoolgroupId>
	<artifactId>hutool-allartifactId>
	<version>5.7.8version>
dependency>

UDP服务器端案例

package cn.demo.udp;

import cn.hutool.cache.CacheUtil;
import cn.hutool.cache.impl.TimedCache;
import cn.hutool.core.date.DateUtil;
import cn.hutool.core.lang.Console;

import java.io.IOException;
import java.net.*;
import java.util.Scanner;
import java.util.Timer;
import java.util.TimerTask;

public class UdpServerTest {

    //定时缓存,默认1秒过期
    private static final TimedCache<String, String> timedCache = CacheUtil.newTimedCache(2000);

    public static void main(String[] args) throws IOException {
        //每5秒清空一次timedCache
        timedCache.schedulePrune(5000);
        //UDP是无连接的，没有像TCP那样的建立连接和保持状态的机制
        //因此这里引入定时缓存，来记录和判断当前可能在线的udp-client
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                Console.log("[{}]------当前可能在线的udp-client-----start--", DateUtil.now());
                if (timedCache.keySet().size() > 0) {
                    for (String s : timedCache.keySet()) {
                        Console.log("------" + s);
                    }
                }
                Console.log("[{}]--------------------------------end--", DateUtil.now());
            }
        }, 1000, 4000);


        //创建一个udp服务器端口为7788的DatagramSocket
        DatagramSocket socket = new DatagramSocket(7788);

        //定义UDP数据包的缓冲区 和 DatagramPacket
        byte[] buffer = new byte[1024 * 64];
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

        while (true) {
            //连续监听,等待接收客户端发送的UDP数据包
            socket.receive(packet);

            //解析 客户端发送的UDP数据包
            int length = packet.getLength();
            String recStr = new String(buffer, 0, length);
            String ip = packet.getAddress().getHostAddress(); //192.168.81.123
            int port = packet.getPort(); //2000
            String netAddr = ip + ":" + port;
            timedCache.put(netAddr, "udp-cli"); //引入定时缓存，来记录和判断当前服务器可能在线的udp-client
            Console.log("[{}] rec-from:{},msg:{}", DateUtil.now(), netAddr, recStr);


            if ("aaa".equals(recStr)) {
                byte[] sendBytes = "bbb!".getBytes();
                socket.send(new DatagramPacket(sendBytes,
                        sendBytes.length,
                        packet.getAddress(),
                        port));

            } else if ("exit".equals(recStr)) {
                byte[] sendBytes = "ok!".getBytes();
                socket.send(new DatagramPacket(sendBytes,
                        sendBytes.length,
                        packet.getAddress(),
                        port));
                Console.log("[{}] {}要主动下线...", DateUtil.now(), netAddr);
                timedCache.remove(netAddr);
            } else {
                byte[] sendBytes = "not-correct-req-data!!!".getBytes();
                socket.send(new DatagramPacket(sendBytes,
                        sendBytes.length,
                        packet.getAddress(),
                        port));
            }
        }



    }
}

UDP客户端案例

package cn.demo.udp;

import cn.hutool.core.date.DateUtil;
import cn.hutool.core.lang.Console;

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

public class UdpClientTest {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket();
        Scanner sc = new Scanner(System.in);


        while (true){
            //------------向udp服务器端发送信息-----------------------------------
            System.out.println("请输入要发送的消息:");
            String input = sc.nextLine();

            //发送报文到7788端口
            byte[] bytes = input.getBytes();
            DatagramPacket packet = new DatagramPacket(bytes, bytes.length,
                    InetAddress.getLocalHost(), 7788);
            socket.send(packet);
            if ("exit".equals(input)){
                System.out.println("udp cli主动下线...");
                socket.close();
                break;
            }

            //------------接收udp服务器返回的消息------------------------
            //定义UDP数据包的缓冲区 和 DatagramPacket
            byte[] buffer = new byte[1024 * 64];
            DatagramPacket packetServerRec = new DatagramPacket(buffer, buffer.length);


            //连续监听,等待接收客户端发送的UDP数据包
            socket.receive(packetServerRec);
            //解析 客户端发送的UDP数据包
            int length = packetServerRec.getLength();
            String recStr = new String(buffer, 0, length);
            String ip = packetServerRec.getAddress().getHostAddress(); //192.168.81.123
            int port = packetServerRec.getPort(); //2000
            String netAddr = ip + ":" + port;
            Console.log("[{}] rec-from-udp-server:{},msg:{}", DateUtil.now(), netAddr, recStr);

        }


    }
}