在互联网时代，网络编程已经成为软件开发不可或缺的一部分。Java作为一种广泛应用于企业级应用开发的语言，其网络编程能力尤为突出。本文将带你从入门到实战，轻松掌握Java网络编程，实现服务器与客户端的通信技巧。

一、Java网络编程基础

1.1 网络编程概念

网络编程是指利用计算机网络的通信协议，实现不同计算机之间的数据传输。Java网络编程主要基于TCP/IP协议，通过Socket实现。

1.2 Java网络编程API

Java网络编程主要依赖于以下API：

  • java.net包：提供网络编程的基础类，如InetAddress、URL、URI等。
  • java.io包：提供输入输出流操作，如InputStream、OutputStream、Reader、Writer等。
  • java.nio包：提供非阻塞I/O操作，如Selector、Channel、ByteBuffer等。

二、Java网络编程实战

2.1 创建TCP服务器

以下是一个简单的TCP服务器示例：

import java.io.*;
import java.net.*;

public class Server {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("服务器已启动，监听端口：" + port);

        while (true) {
            Socket socket = serverSocket.accept();
            new Thread(new ClientHandler(socket)).start();
        }
    }
}

class ClientHandler implements Runnable {
    private Socket socket;

    public ClientHandler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                System.out.println("客户端：" + inputLine);
                out.println("服务器：" + inputLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2.2 创建TCP客户端

以下是一个简单的TCP客户端示例：

import java.io.*;
import java.net.*;

public class Client {
    public static void main(String[] args) throws IOException {
        String host = "localhost";
        int port = 12345;

        Socket socket = new Socket(host, port);
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));

        String userInput;
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("服务器：" + in.readLine());
        }

        socket.close();
    }
}

2.3 创建UDP服务器

以下是一个简单的UDP服务器示例：

import java.io.*;
import java.net.*;

public class UdpServer {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        DatagramSocket serverSocket = new DatagramSocket(port);
        System.out.println("UDP服务器已启动，监听端口：" + port);

        while (true) {
            byte[] receiveData = new byte[1024];
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket);

            String sentence = new String(receivePacket.getData(), 0, receivePacket.getLength());
            System.out.println("客户端：" + sentence);

            InetAddress IPAddress = receivePacket.getAddress();
            int port = receivePacket.getPort();
            byte[] sendData = sentence.getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
            serverSocket.send(sendPacket);
        }
    }
}

2.4 创建UDP客户端

以下是一个简单的UDP客户端示例：

import java.io.*;
import java.net.*;

public class UdpClient {
    public static void main(String[] args) throws IOException {
        String host = "localhost";
        int port = 12345;

        InetAddress IPAddress = InetAddress.getByName(host);
        byte[] sendData = "Hello, UDP server!".getBytes();
        DatagramSocket socket = new DatagramSocket();
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
        socket.send(sendPacket);

        byte[] receiveData = new byte[1024];
        DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
        socket.receive(receivePacket);

        String modifiedSentence = new String(receivePacket.getData(), 0, receivePacket.getLength());
        System.out.println("服务器：" + modifiedSentence);

        socket.close();
    }
}

三、总结

通过本文的学习，相信你已经掌握了Java网络编程的基础知识和实战技巧。在实际开发中，你可以根据需求选择合适的网络编程方式，实现服务器与客户端之间的通信。祝你编程愉快！