UDP就是將目的地和資料封裝在一個包中，然後傳送給相應的目的地，包的大小最大為64K，安全性低，效率高

在建立之前我們餘姚知道一些類和方法的用法

比如：InetAdress類

//得到名為zhang的主機物件
InetAddress iAddress=InetAddress.getByName("zhang");
//得到該物件的ip地址
String hostIp=iAddress.getHostAddress();
//獲得本地主機物件
InetAddress iAddress2=InetAddress.getLocalHost();
//得到該物件的ip地址
String hostip1=iAddress2.getHostAddress();
//得到該主機的名字
String hostName=iAddress2.getHostName();
//得到名為zhang的計算機的所有ipv4和ipv6連結
InetAddress[] iAddress3=InetAddress.getAllByName("zhang");
for (int i = 0; i < iAddress3.length; i++) {
	System.out.println(iAddress3[i].getHostAddress());
}
 

DatagramSocket ds=new DatagramSocket();

DatagramPacket dp=new DatagramPacket();

UDP發包

package net;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.Scanner;

public class UDPClient implements Runnable {

	//目的埠
	private int port;

	//目的ip
	private String ip;

	//初始化ip和埠
	public UDPClient(String ip, int port) {
		super();
		this.ip = ip;
		this.port = port;
	}
	@Override
	public void run() {
		UDPClient uClient=new UDPClient(ip, port);
		uClient.UDPClient();
	}
	public void UDPClient() {
		//定義socket物件，實現通訊
		DatagramSocket dSocket = null;
		//高效讀
		BufferedReader bReader = null;
		try {
			//得到目的ip的主機物件
			InetAddress iAddress1=InetAddress.getByName(ip);
			System.out.println("已接入"+iAddress1.getHostName());
			while (true) {
				//從控制檯讀取
				bReader = new BufferedReader(new InputStreamReader(System.in));
				//讀取一行資料
				String string = bReader.readLine();
				//定義socket物件，實現通訊
				dSocket = new DatagramSocket();
				//把讀到的字串轉碼為utf-8字元陣列
				byte[] by = string.getBytes("utf-8");//兩個客戶端務必編碼一致，不然會亂碼
				InetAddress iAddress = InetAddress.getByName(ip);
				//建立資料包
				DatagramPacket dPacket = new DatagramPacket(by, by.length, iAddress, port);
				//傳送資料包
				dSocket.send(dPacket);
				System.out.println("你對" + iAddress.getHostName() + "說:" + string);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (dSocket != null) {
				dSocket.close();
			}
		}
	}

}
 

UDP收包

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

public class UDPServer implements Runnable {

	//接受埠
	private int port;

	//構造器，初始化埠
	public UDPServer(int port) {
		super();
		this.port = port;
	}

	@Override
	public void run() {
		UDPServer uServer=new UDPServer(port);
		uServer.udpServer();
	}
	public void udpServer() {
		//設定socket通訊
		DatagramSocket dSocket = null;
		try {
			dSocket = new DatagramSocket(port);
			//接受的位元組大小
			byte[] by = new byte[1024];
			//無限監聽
			while (true) {
				//定義一個數據包物件
				DatagramPacket dPacket = new DatagramPacket(by, by.length);
				//接受資料包
				dSocket.receive(dPacket);
				//獲得資料包中的資料
				byte by1[] = dPacket.getData();
				//獲得資料包中資料的長度
				int len = dPacket.getLength();
				//以字串的形式輸出
				System.out.println(dPacket.getAddress() + "對你說:" + new String(by1, 0, len));
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			dSocket.close();
		}
	}
}
 

這時，我們需要再定義一個聊天室物件

CharRom

一個客戶端

package net;


public class ChatRom implements Runnable {

	@Override
	public void run() {
		//一個客戶端
		//發到10000埠，10001埠接受
		Thread thread=new Thread(new UDPClient("192.168.1.44", 10000));
		Thread thread1=new Thread(new UDPServer(10001));
		thread.start();
		thread1.start();
	}
}

另一個客戶端

package net;


public class ChatRom implements Runnable {

	@Override
	public void run() {
		//另一個客戶端
		//發到10001埠，10000埠接受
		Thread thread=new Thread(new UDPClient("192.168.1.11", 10001));
		Thread thread1=new Thread(new UDPServer(10000));
		thread.start();
		thread1.start();
	}
}

然後分別在兩個客戶端執行

package net;

public class Chatdemo {
	public static void main(String[] args) {
		ChatRom chatRom=new ChatRom();
		Thread thread=new Thread(chatRom);
		thread.start();
	}
}

好了，聊天室製作完成

總結：

根據UDP特點，傳送端和接收端需要執行緒同時執行，且使用的埠不一樣，注意發包的時候和接包的時候編碼一致，不然會亂碼