原理從簡單到複雜遞進,代碼從少到多實現
簡介:
UDP無連接,不穩定
客戶端和服務端:沒有明確的界限不管有沒有準備好,都可以發給你導彈
DDos:洪水攻擊(飽和攻擊)
利用此原理可以實現發短信功能,不需要雙方在線接收消息,一個只要將消息發送出去,另外一個可以隨緣就接收,這點與TCP實現通信相反,在我看來TCP實現通信類似於打電話,必須雙方同時在線.
源碼展示:
客戶端:
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//UDP不需要連接服務器
public class UdpClientDemo01 {
public static void main(String[] args) throws Exception{ //1.建立一個Socket
DatagramSocket socket=new DatagramSocket();
//2.建一個包
String msg="你好呀,服務器!";
//發送給誰
InetAddress localhost = InetAddress.getByName("localhost");
int port =9090; DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
//3.發送包
socket.send(packet); //關閉流
socket.close();
服務器端:
package com.lesson03;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//UDP不需要連接服務器
public class UdpClientDemo01 {
public static void main(String[] args) throws Exception{
//1.建立一個Socket
DatagramSocket socket=new DatagramSocket();
//2.建一個包
String msg="你好呀,服務器!";
//發送給誰
InetAddress localhost = InetAddress.getByName("localhost");
int port =9090;
DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
//3.發送包
socket.send(packet);
//關閉流
socket.close();
}
}
由客戶端,服務器端,可以轉變爲兩個用戶之間的通信
開啓線程,實現雙方相互通信:首先實現兩個方法:接收方,和發送方!注意兩個類都實現了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);
//準備數據,控制檯讀取system.in
reader = new BufferedReader(new InputStreamReader(System.in));
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void run() { //準備數據,控制檯讀取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 {
//準備接收的包裹
byte[] container = new byte[1024];
DatagramPacket packet = new DatagramPacket(container,0,container.length);
socket.receive(packet);//阻塞式接收包裹
//斷開連接的判斷
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();
}
}
}
}
定義兩個對象,來開啓線程.核心代碼就是new Thread().start,注意端口號是否一致!
Boss:
package com.qiu.chat;public class TalkStudent {
public static void main(String[] args) {
//開啓兩個線程
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();
}
}
代碼實現之後,即可實現boss與employee之間的通信.