UDP消息发送基础源码以及UDP实现多线程聊天

原理从简单到复杂递进,代码从少到多实现
简介:
UDP无连接，不稳定
客户端和服务端：没有明确的界限不管有没有准备好，都可以发给你导弹
DDos：洪水攻击（饱和攻击）
利用此原理可以实现发短信功能,不需要双方在线接收消息,一个只要将消息发送出去,另外一个可以随缘就接收,这点与TCP实现通信相反,在我看来TCP实现通信类似于打电话,必须双方同时在线.
源码展示:
客户端:

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//UDP不需要连接服务器
public class UdpClientDemo01 {
    public static void main(String[] args) throws Exception{    //1.建立一个Socket
    DatagramSocket socket=new DatagramSocket();
    //2.建一个包
        String msg="你好呀,服务器!";
        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port =9090;        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
        //3.发送包
        socket.send(packet);        //关闭流
        socket.close();

服务器端:

package com.lesson03;

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

//UDP不需要连接服务器
public class UdpClientDemo01 {
    public static void main(String[] args) throws Exception{

    //1.建立一个Socket
    DatagramSocket socket=new DatagramSocket();
    //2.建一个包
        String msg="你好呀,服务器!";
        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port =9090;

        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
        //3.发送包
        socket.send(packet);

        //关闭流
        socket.close();
}
}

由客户端,服务器端,可以转变为两个用户之间的通信
开启线程,实现双方相互通信:首先实现两个方法:接收方,和发送方!注意两个类都实现了Runable接口talkSend:

talkSend:package com.qiu.chat;import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;public class TalkSend implements Runnable {
    DatagramSocket socket=null;
    BufferedReader reader =null;
    private int fromPort;
    private String toIp;
    private int toPort;    public TalkSend(int fromPort, String toIp, int toPort) {
        this.fromPort = fromPort;
        this.toIp = toIp;
        this.toPort = toPort;        try {
            socket = new DatagramSocket(fromPort);
            //准备数据,控制台读取system.in
            reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    @Override
    public void run() {        //准备数据,控制台读取system.in        while (true) {
        try {  String data = reader.readLine();
            byte[] datas = data.getBytes();            DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress(this.toIp,this.toPort));
            socket.send(packet);
            if (data.equals("bye")) {
                break;
            }
        }catch (Exception e) {
            e.printStackTrace();            }
        }
        socket.close();
    }
}

talkReceive:

package com.qiu.chat;import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;public class TalkReceive implements Runnable {    DatagramSocket socket =null;
    private int port;
    private String msgFrom;    public TalkReceive(int port,String msgFrom) {
        this.port = port;
        this.msgFrom=msgFrom;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }    @Override
    public void run() {        while (true) {
            try {
                //准备接收的包裹
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container,0,container.length);
                socket.receive(packet);//阻塞式接收包裹
                //断开连接的判断
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
                System.out.println(msgFrom+":"+receiveData);
                if(receiveData.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
      }
    }
}

定义两个对象,来开启线程.核心代码就是new Thread().start,注意端口号是否一致!
Boss:

package com.qiu.chat;public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend(7195,"LocalHost",10086)).start();
        new Thread(new TalkReceive(10010,"Boss")).start();
    }
}

employee:

package com.qiu.chat;public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSend(10000,"LocalHost",10010)).start();
        new Thread(new TalkReceive(10086,"employee")).start();
    }
    }

代码实现之后,即可实现boss与employee之间的通信.