在当今这个互联网时代，网络编程已经成为软件开发中的一个重要技能。Java作为一种广泛应用于企业级应用的语言，其强大的网络编程能力更是不容小觑。本文将从实战案例出发，带你轻松入门Java网络编程，一步步打造自己的网络应用。

一、Java网络编程基础

1. 网络编程概念

网络编程是指通过计算机网络实现不同计算机之间的通信和数据交换。Java网络编程主要依赖于Java标准库中的java.net包。

2. Java网络编程模型

Java网络编程主要分为两种模型：阻塞IO和非阻塞IO。阻塞IO是指程序在等待网络请求完成时，会暂停执行；非阻塞IO则允许程序在等待过程中继续执行其他任务。

二、Java网络编程实战案例

1. TCP客户端与服务器

客户端

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class TCPClient {
    public static void main(String[] args) {
        try {
            Socket socket = new Socket("127.0.0.1", 12345);
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out.println("Hello, Server!");
            System.out.println("Server response: " + in.readLine());
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

服务器

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(12345);
            while (true) {
                Socket socket = serverSocket.accept();
                BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                String line = in.readLine();
                System.out.println("Client says: " + line);
                out.println("Hello, Client!");
                socket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2. UDP客户端与服务器

客户端

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPClient {
    public static void main(String[] args) {
        try {
            DatagramSocket socket = new DatagramSocket();
            String message = "Hello, Server!";
            byte[] buf = message.getBytes();
            DatagramPacket packet = new DatagramPacket(buf, buf.length, "127.0.0.1", 12345);
            socket.send(packet);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            String response = in.readLine();
            System.out.println("Server response: " + response);
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

服务器

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPServer {
    public static void main(String[] args) {
        try {
            DatagramSocket socket = new DatagramSocket(12345);
            while (true) {
                byte[] buf = new byte[1024];
                DatagramPacket packet = new DatagramPacket(buf, buf.length);
                socket.receive(packet);
                String message = new String(packet.getData(), 0, packet.getLength());
                System.out.println("Client says: " + message);
                String response = "Hello, Client!";
                byte[] responseBytes = response.getBytes();
                DatagramPacket responsePacket = new DatagramPacket(responseBytes, responseBytes.length, packet.getAddress(), packet.getPort());
                socket.send(responsePacket);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3. HTTP客户端与服务器

客户端

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class HTTPClient {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://www.example.com");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            System.out.println("Response: " + response.toString());
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

服务器

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class HTTPServer {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(80);
            while (true) {
                Socket socket = serverSocket.accept();
                BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String request = in.readLine();
                System.out.println("Request: " + request);
                OutputStream out = socket.getOutputStream();
                out.write("HTTP/1.1 200 OK\r\n\r\n".getBytes());
                out.write("Hello, World!".getBytes());
                out.close();
                socket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

三、总结

通过以上实战案例，相信你已经对Java网络编程有了初步的了解。接下来，你可以根据自己的需求，深入学习Java网络编程的其他方面，如多线程、SSL/TLS等。祝你学习愉快！