What are the commonly used protocols and libraries in Java network programming?

import java.net.HttpURLConnection;
import java.net.URL;

public class HttpGetExample {

    public static void main(String[] args) throws Exception {
        String url = "https://www.example.com";

        // 创建 HttpURLConnection
        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();

        // 设置请求方法和内容类型
        con.setRequestMethod("GET");
        con.setRequestProperty("Content-Type", "application/json");

        // 发送请求并获取响应代码
        int responseCode = con.getResponseCode();

        // 打印响应正文
        System.out.println("Response Code: " + responseCode);
        Scanner scanner = new Scanner(con.getInputStream());
        while (scanner.hasNextLine()) {
            System.out.println(scanner.nextLine());
        }
        scanner.close();
    }
}

import java.net.ServerSocket;
import java.net.Socket;

public class TcpServerExample {

    public static void main(String[] args) throws Exception {
        // 监听端口
        int port = 8080;

        // 创建 ServerSocket
        ServerSocket serverSocket = new ServerSocket(port);

        // 循环等待客户端连接
        while (true) {
            // 接受客户端连接
            Socket clientSocket = serverSocket.accept();
            
            // 创建新线程处理客户端连接
            Thread thread = new Thread(() -> {
                try {
                    // 获取客户端输入流
                    BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                    
                    // 打印客户端发来的数据
                    String line;
                    while ((line = in.readLine()) != null) {
                        System.out.println("Message from client: " + line);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
            thread.start();
        }
    }
}