Java UDP 통신의 원리는 무엇입니까

package test; import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; /** * UDPCLient deom * @author  */ public class UDPClient { public static void main(String[] args) throws Exception { DatagramSocket clientSocket = new DatagramSocket(); BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in) ); //获取本地 IP 地址 InetAddress IPAddress = InetAddress.getLocalHost(); byte[] sendData; byte[] receiveData = new byte[1024]; System.out.println("请输入一句英文，服务器会返回其大写形式（输入exit退出）"); while (true) { String sentence = inFromUser.readLine(); if (sentence.equals("exit")) break; sendData = sentence.getBytes(); //创建发送数据报包，并标注源地址#，目的地址# DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); //发送数据报包 clientSocket.send(sendPacket); //创建接收数据报包 DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); //接收服务器的数据报包 clientSocket.receive(receivePacket); String modifiedSentence = new String(receivePacket.getData()); System.out.println("FROM SERVER: " + modifiedSentence); } clientSocket.close(); } }