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

Commonly used protocols and libraries for Java network programming: Protocols: TCP, UDP, HTTP, HTTPS, FTP Library: java.net, java.nio, Apache HttpClient, Netty, OkHttp

Commonly used protocols and libraries in Java network programming

Java provides a wealth of libraries and frameworks to simplify network programming. Some commonly used protocols and libraries are listed below:

Protocol

• TCP (Transmission Control Protocol): A connection-oriented protocol that provides reliable, ordered data transmission.
• UDP (User Datagram Protocol): A connectionless protocol that provides low-overhead, unreliable data transmission.
• HTTP (Hypertext Transfer Protocol): Protocol used to obtain resources from a web server.
• HTTPS (Hypertext Transfer Protocol Secure): A secure version of HTTP that uses TLS/SSL to encrypt data transmission.
• FTP (File Transfer Protocol): A protocol used to transfer files between clients and servers.

Library

• java.net: The basic library for network programming in Java, providing basic network execution Operation methods and classes.
• java.nio: Provides a higher-level network API based on NIO (non-blocking I/O), allowing multi-threaded processing of network events.
• Apache HttpClient: A popular and easy-to-use HTTP client that provides high-level methods for sending and receiving HTTP requests.
• Netty: A high-performance I/O framework that provides support for multiple protocols, including TCP, UDP, and HTTP.
• OkHttp: A lightweight and asynchronous HTTP client optimized for mobile devices.

Practical case

Send HTTP GET request

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();
    }
}

Create TCP server

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();
        }
    }
}

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