//構(gòu)造方法，創(chuàng)建數(shù)據(jù)報套接字并將其綁定到本地主機上的指定端口
DatagramSocket socket = new DatagramSocket(0);

/*
 * 服務(wù)器端，實現(xiàn)基于UDP的用戶登陸
 */
public class UDPServer {
  public static void main(String[] args) throws IOException {
    /*
     * 接收客戶端發(fā)送的數(shù)據(jù)
     */
    // 1.創(chuàng)建服務(wù)器端DatagramSocket，指定端口
    DatagramSocket socket = new DatagramSocket(8800);
    // 2.創(chuàng)建數(shù)據(jù)報，用于接收客戶端發(fā)送的數(shù)據(jù)
    byte[] data = new byte[1024];// 創(chuàng)建字節(jié)數(shù)組，指定接收的數(shù)據(jù)包的大小
    DatagramPacket packet = new DatagramPacket(data, data.length);
    // 3.接收客戶端發(fā)送的數(shù)據(jù)
    System.out.println("****服務(wù)器端已經(jīng)啟動，等待客戶端發(fā)送數(shù)據(jù)");
    socket.receive(packet);// 此方法在接收到數(shù)據(jù)報之前會一直阻塞
    // 4.讀取數(shù)據(jù)
    String info = new String(data, 0, packet.getLength());
    System.out.println("我是服務(wù)器，客戶端說：" + info);
 
    /*
     * 向客戶端響應(yīng)數(shù)據(jù)
     */
    // 1.定義客戶端的地址、端口號、數(shù)據(jù)
    InetAddress address = packet.getAddress();
    int port = packet.getPort();
    byte[] data2 = "歡迎您!".getBytes();
    // 2.創(chuàng)建數(shù)據(jù)報，包含響應(yīng)的數(shù)據(jù)信息
    DatagramPacket packet2 = new DatagramPacket(data2, data2.length, address, port);
    // 3.響應(yīng)客戶端
    socket.send(packet2);
    // 4.關(guān)閉資源
    socket.close();
  }
}

/*
 * 客戶端
 */
public class UDPClient {
  public static void main(String[] args) throws IOException {
    /*
     * 向服務(wù)器端發(fā)送數(shù)據(jù)
     */
    // 1.定義服務(wù)器的地址、端口號、數(shù)據(jù)
    InetAddress address = InetAddress.getByName("localhost");
    int port = 8800;
    byte[] data = "用戶名：admin;密碼：123".getBytes();
    // 2.創(chuàng)建數(shù)據(jù)報，包含發(fā)送的數(shù)據(jù)信息
    DatagramPacket packet = new DatagramPacket(data, data.length, address, port);
    // 3.創(chuàng)建DatagramSocket對象
    DatagramSocket socket = new DatagramSocket();
    // 4.向服務(wù)器端發(fā)送數(shù)據(jù)報
    socket.send(packet);
 
    /*
     * 接收服務(wù)器端響應(yīng)的數(shù)據(jù)
     */
    // 1.創(chuàng)建數(shù)據(jù)報，用于接收服務(wù)器端響應(yīng)的數(shù)據(jù)
    byte[] data2 = new byte[1024];
    DatagramPacket packet2 = new DatagramPacket(data2, data2.length);
    // 2.接收服務(wù)器響應(yīng)的數(shù)據(jù)
    socket.receive(packet2);
    // 3.讀取數(shù)據(jù)
    String reply = new String(data2, 0, packet2.getLength());
    System.out.println("我是客戶端，服務(wù)器說：" + reply);
    // 4.關(guān)閉資源
    socket.close();
  }
}