没有多线程

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Stack;

public class MyUDB {

    /**
     * UDP服务端
     * @throws IOException
     */
    public static void UDPserver() throws IOException {
        //1.创建服务器端DatagtamSocket，指定端口号
        DatagramSocket socket = new DatagramSocket(2505);
        //2.创建数据报，用于接收客服端发送的数据
        byte[] data = new byte[1024];//创建字节数组，指定数据报的大小
        DatagramPacket packet = new DatagramPacket(data, data.length);//
        //3.接收客服端发送的消息
        System.out.println("服务器已经启动。。。。。。。。。");
        socket.receive(packet);//此方法在收到数据之前会一直阻塞
        //4.读取数据
        String info = new String(data,0,packet.getLength());
        System.out.println("服务器说"+info);
        /*
         * 响应客服端数据
         * */
        //1.定义客服端的地址、端口号、数据     
        InetAddress address = packet.getAddress();
        int port = packet.getPort();
        byte[]  data2 = "欢迎你".getBytes();
        //2.创建数据报，包含响应的数据信息
        DatagramPacket packet2 = new DatagramPacket(data2, data2.length,address,port);
        //3.响应客服端
        socket.send(packet2);
        //4.关闭资源
        socket.close();

    }

    /**
     * UDP客服端
     * @throws IOException
     */
    public static void  UDPclient() throws IOException {
        // 1.定义服务器的地址、端口号、数据        
        InetAddress address = InetAddress.getByName("202.202.43.125");
        int port = 2505;
        byte[] data ="我是客服端".getBytes();
        //2.创建数据报，包含发送的数据信息
        DatagramPacket packet = new DatagramPacket(data, data.length,address,port);
        //3.创建DatagramSocket对象
        DatagramSocket socket = new DatagramSocket();
        //4.向服务器发送数据报
        socket.send(packet);

        /*
         * 接收服务器端的数据
         * */
        //1.创建数据报，用于接收服务器端响应的数据
        byte[] data2 = new byte[1024];
        DatagramPacket packet2 = new DatagramPacket(data2, data2.length);
        //2.接收服务器响应的数据
        socket.receive(packet2);
        //3.读取数据
        String reply = new String(data2,0,packet2.getLength());
        System.out.println("服务器说:"+reply);
        //4.关闭资源
        socket.close();
    }
}