简介
Java网络编程是一种通过网络连接和通信来实现应用程序之间数据传输的技术。它允许不同设备上的应用程序互相交流，从而实现各种功能，如文件传输、消息传递、远程方法调用等。本指南将介绍Java网络编程的基础概念和实际应用。

目录
Socket编程
Socket基础
TCP和UDP
服务器-客户端通信
创建服务器
创建客户端
HTTP通信
HTTP请求
HTTP响应
RMI远程方法调用
创建RMI服务
创建RMI客户端

Socket编程

Socket基础

Socket是Java网络编程的基本组成部分，它允许应用程序通过网络发送和接收数据。Socket通常分为两种类型：客户端Socket和服务器Socket。了解如何创建和使用Socket是进行网络编程的第一步。

// 创建客户端Socket
Socket clientSocket = new Socket("服务器地址", 端口号);// 创建服务器Socket
ServerSocket serverSocket = new ServerSocket(端口号);
Socket clientSocket = serverSocket.accept();

TCP和UDP

Java支持两种主要的网络传输协议：TCP（传输控制协议）和UDP（用户数据报协议）。它们在数据传输时有不同的特性和用途。

TCP：提供可靠的、面向连接的数据传输。适用于需要确保数据完整性和顺序的应用。
UDP：提供无连接、不可靠的数据传输。适用于实时性要求较高、可以容忍数据丢失的应用。

服务器-客户端通信

创建服务器

创建一个基本的Java服务器，以便接受来自客户端的连接请求和数据传输。

import java.io.*;
import java.net.*;public class MyServer {public static void main(String[] args) {try {ServerSocket serverSocket = new ServerSocket(端口号);Socket clientSocket = serverSocket.accept();// 处理客户端连接和数据传输} catch (IOException e) {e.printStackTrace();}}
}

创建客户端

创建一个基本的Java客户端，以便连接到服务器并进行数据传输。

import java.io.*;
import java.net.*;public class MyClient {public static void main(String[] args) {try {Socket clientSocket = new Socket("服务器地址", 端口号);// 处理与服务器的连接和数据传输} catch (IOException e) {e.printStackTrace();}}
}

HTTP通信

HTTP请求

使用Java发送HTTP请求，与远程服务器进行通信并获取数据。

import java.net.*;
import java.io.*;public class HttpRequestExample {public static void main(String[] args) {try {URL url = new URL("http://example.com");HttpURLConnection connection = (HttpURLConnection) url.openConnection();connection.setRequestMethod("GET");// 处理HTTP响应} catch (IOException e) {e.printStackTrace();}}
}

HTTP响应

处理从远程服务器接收的HTTP响应。

import java.net.*;
import java.io.*;public class HttpResponseExample {public static void main(String[] args) {try {URL url = new URL("http://example.com");HttpURLConnection connection = (HttpURLConnection) url.openConnection();connection.setRequestMethod("GET");int responseCode = connection.getResponseCode();// 读取响应数据} catch (IOException e) {e.printStackTrace();}}
}

RMI远程方法调用

创建RMI服务

创建一个基本的RMI服务，以便远程调用服务器上的方法。

import java.rmi.*;
import java.rmi.server.*;public class MyRemoteServer extends UnicastRemoteObject implements MyRemoteInterface {public MyRemoteServer() throws RemoteException {// 构造函数}public String sayHello() throws RemoteException {return "Hello, 远程世界!";}public static void main(String[] args) {try {MyRemoteServer remoteServer = new MyRemoteServer();Naming.rebind("MyRemoteServer", remoteServer);} catch (Exception e) {e.printStackTrace();}}
}

创建RMI客户端

创建一个基本的RMI客户端，以便调用远程服务器上的方法。

import java.rmi.*;public class MyRemoteClient {public static void main(String[] args) {try {MyRemoteInterface remoteService = (MyRemoteInterface) Naming.lookup("rmi://服务器地址/MyRemoteServer");String response = remoteService.sayHello();System.out.println("远程服务器响应: " + response);} catch (Exception e) {e.printStackTrace();}}
}

以上文档提供了Java网络编程的基础知识和示例代码。你可以根据自己的需求和学习进度来进一步深入研究和扩展这些主题。

多人聊天室

这个简单的聊天室示例允许多个客户端通过输入消息与服务器进行通信，服务器会将接收到的消息广播给所有连接的客户端。客户端和服务器之间的通信是基于Socket实现的。确保将服务器地址和端口号与你的实际配置相匹配。

package chatting;import java.io.*;
import java.net.*;
import java.util.*;
import java.util.concurrent.*;public class ChatServer {private static final int PORT = 12345;private static Set<PrintWriter> clientWriters = new CopyOnWriteArraySet<>();public static void main(String[] args) {System.out.println("Chat Server is running...");ExecutorService pool = Executors.newFixedThreadPool(10);try (ServerSocket serverSocket = new ServerSocket(PORT)) {while (true) {new ClientHandler(serverSocket.accept(), pool).start();}} catch (IOException e) {e.printStackTrace();}}private static class ClientHandler extends Thread {private Socket socket;private PrintWriter out;private BufferedReader in;private ExecutorService pool;public ClientHandler(Socket socket, ExecutorService pool) {this.socket = socket;this.pool = pool;}public void run() {try {in = new BufferedReader(new InputStreamReader(socket.getInputStream()));out = new PrintWriter(socket.getOutputStream(), true);clientWriters.add(out);String message;while ((message = in.readLine()) != null) {System.out.println("Received: " + message);broadcast(message);}} catch (IOException e) {e.printStackTrace();} finally {try {socket.close();} catch (IOException e) {e.printStackTrace();}clientWriters.remove(out);}}private void broadcast(String message) {for (PrintWriter writer : clientWriters) {writer.println(message);}}}
}

class ChatClientUser {public static void main(String[] args) {final String SERVER_ADDRESS = "localhost";final int SERVER_PORT = 12345;try (Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT)) {PrintWriter out = new PrintWriter(socket.getOutputStream(), true);BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));Scanner scanner = new Scanner(System.in);Thread inputThread = new Thread(() -> {try {String userInput;while ((userInput = scanner.nextLine()) != null) {out.println(userInput);}} catch (Exception e) {e.printStackTrace();}});inputThread.start();String serverResponse;while ((serverResponse = in.readLine()) != null) {System.out.println("Received from server: " + serverResponse);}} catch (IOException e) {e.printStackTrace();}}
}class ChatClientUserA {public static void main(String[] args) {final String SERVER_ADDRESS = "localhost";final int SERVER_PORT = 12345;try (Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT)) {PrintWriter out = new PrintWriter(socket.getOutputStream(), true);BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));Scanner scanner = new Scanner(System.in);Thread inputThread = new Thread(() -> {try {String userInput;while ((userInput = scanner.nextLine()) != null) {out.println(userInput);}} catch (Exception e) {e.printStackTrace();}});inputThread.start();String serverResponse;while ((serverResponse = in.readLine()) != null) {System.out.println("Received from server: " + serverResponse);}} catch (IOException e) {e.printStackTrace();}}
}class ChatClientUserB {public static void main(String[] args) {final String SERVER_ADDRESS = "localhost";final int SERVER_PORT = 12345;try (Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT)) {PrintWriter out = new PrintWriter(socket.getOutputStream(), true);BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));Scanner scanner = new Scanner(System.in);Thread inputThread = new Thread(() -> {try {String userInput;while ((userInput = scanner.nextLine()) != null) {out.println(userInput);}} catch (Exception e) {e.printStackTrace();}});inputThread.start();String serverResponse;while ((serverResponse = in.readLine()) != null) {System.out.println("Received from server: " + serverResponse);}} catch (IOException e) {e.printStackTrace();}}
}