掌握Java网络编程核心技术（从Socket到多线程服务器实战指南）

第一个Java Socket程序：客户端与服务器

我们先从最简单的TCP通信开始。TCP是面向连接的协议，保证数据可靠传输。

服务器端代码

import java.io.*;import java.net.*;public class SimpleServer {    public static void main(String[] args) {        try (ServerSocket serverSocket = new ServerSocket(8080)) {            System.out.println("服务器已启动，监听端口 8080...");                        while (true) {                Socket clientSocket = serverSocket.accept();                System.out.println("新客户端连接: " + clientSocket.getInetAddress());                                // 读取客户端消息                BufferedReader in = new BufferedReader(                    new InputStreamReader(clientSocket.getInputStream())                );                PrintWriter out = new PrintWriter(                    clientSocket.getOutputStream(), true                );                                String inputLine;                while ((inputLine = in.readLine()) != null) {                    System.out.println("收到: " + inputLine);                    out.println("服务器已收到: " + inputLine);                }                                clientSocket.close();            }        } catch (IOException e) {            e.printStackTrace();        }    }}

客户端代码

import java.io.*;import java.net.*;public class SimpleClient {    public static void main(String[] args) {        try (Socket socket = new Socket("localhost", 8080);             PrintWriter out = new PrintWriter(socket.getOutputStream(), true);             BufferedReader in = new BufferedReader(                 new InputStreamReader(socket.getInputStream())             )) {                        // 发送消息            out.println("Hello, Java网络编程!");                        // 接收响应            String response = in.readLine();            System.out.println("服务器回复: " + response);                    } catch (IOException e) {            e.printStackTrace();        }    }}

提升性能：构建多线程服务器

上面的服务器一次只能处理一个客户端。为了支持并发，我们需要为每个客户端创建一个独立线程——这就是多线程服务器的核心思想。

// 客户端处理线程class ClientHandler implements Runnable {    private Socket clientSocket;        public ClientHandler(Socket socket) {        this.clientSocket = socket;    }        @Override    public void run() {        try (            BufferedReader in = new BufferedReader(                new InputStreamReader(clientSocket.getInputStream())            );            PrintWriter out = new PrintWriter(                clientSocket.getOutputStream(), true            )        ) {            String inputLine;            while ((inputLine = in.readLine()) != null) {                System.out.println("来自 " + clientSocket.getInetAddress() + ": " + inputLine);                out.println("Echo: " + inputLine);            }        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                clientSocket.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }}// 主服务器public class MultiThreadedServer {    public static void main(String[] args) {        try (ServerSocket serverSocket = new ServerSocket(8080)) {            System.out.println("多线程服务器启动，端口 8080...");                        while (true) {                Socket clientSocket = serverSocket.accept();                Thread thread = new Thread(new ClientHandler(clientSocket));                thread.start(); // 为每个客户端启动新线程            }        } catch (IOException e) {            e.printStackTrace();        }    }}

UDP通信简介

除了TCP，Java也支持UDP（用户数据报协议）。UDP不建立连接，速度快但不可靠，适用于视频流、游戏等场景。

// UDP 服务器DatagramSocket socket = new DatagramSocket(9000);byte[] buffer = new byte[1024];DatagramPacket packet = new DatagramPacket(buffer, buffer.length);socket.receive(packet);String received = new String(packet.getData(), 0, packet.getLength());System.out.println("收到UDP消息: " + received);// 回复客户端InetAddress address = packet.getAddress();int port = packet.getPort();DatagramPacket reply = new DatagramPacket(    "OK".getBytes(), 2, address, port);socket.send(reply);

总结与进阶方向

通过本教程，你已经掌握了Java网络编程的基础：从简单的Socket通信，到支持并发的多线程服务器，再到UDP协议的使用。这些是构建任何网络应用的基石。

下一步，你可以探索：

• NIO（非阻塞IO）与Netty框架
• HTTP服务器实现（如用Socket解析HTTP请求）
• SSL/TLS加密通信
• WebSocket实时通信

记住，真正的Java高级网络开发不仅在于写代码，更在于理解协议、优化性能、保障安全。动手实践吧！