【Java 基础篇】Java网络编程实战：P2P文件共享详解

import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.util.List;

// 用于表示文件的数据结构
class SharedFile {
    String name;
    long size;

    public SharedFile(String name, long size) {
        this.name = name;
        this.size = size;
    }
}

// P2P客户端
class P2PClient {
    private String serverAddress;
    private int serverPort;
    private List<SharedFile> sharedFiles;

    public P2PClient(String serverAddress, int serverPort) {
        this.serverAddress = serverAddress;
        this.serverPort = serverPort;
        this.sharedFiles = new ArrayList<>();
    }

    public void start() {
        // 连接到P2P服务器并进行文件共享协议的交互
        try (Socket socket = new Socket(serverAddress, serverPort);
             ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
             ObjectInputStream in = new ObjectInputStream(socket.getInputStream())) {

            // 向服务器注册共享文件列表
            out.writeObject(sharedFiles);

            // 循环等待来自其他客户端的下载请求
            while (true) {
                DownloadRequest request = (DownloadRequest) in.readObject();
                if (request != null) {
                    handleDownloadRequest(request);
                }
            }

        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    private void handleDownloadRequest(DownloadRequest request) {
        // 根据请求中的文件名查找文件并发送数据给请求的客户端
        for (SharedFile file : sharedFiles) {
            if (file.name.equals(request.getFileName())) {
                try (Socket dataSocket = new Socket(request.getRequestingClientAddress(), request.getRequestingClientPort());
                     FileInputStream fileInputStream = new FileInputStream(file.name);
                     OutputStream dataOutputStream = dataSocket.getOutputStream()) {

                    byte[] buffer = new byte[1024];
                    int bytesRead;

                    while ((bytesRead = fileInputStream.read(buffer)) != -1) {
                        dataOutputStream.write(buffer, 0, bytesRead);
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public void addSharedFile(String filePath) {
        // 将文件添加到共享文件列表
        File file = new File(filePath);
        if (file.exists() && file.isFile()) {
            sharedFiles.add(new SharedFile(file.getName(), file.length()));
        }
    }
}

// 下载请求类
class DownloadRequest implements Serializable {
    private String fileName;
    private String requestingClientAddress;
    private int requestingClientPort;

    public DownloadRequest(String fileName, String requestingClientAddress, int requestingClientPort) {
        this.fileName = fileName;
        this.requestingClientAddress = requestingClientAddress;
        this.requestingClientPort = requestingClientPort;
    }

    public String getFileName() {
        return fileName;
    }

    public String getRequestingClientAddress() {
        return requestingClientAddress;
    }

    public int getRequestingClientPort() {
        return requestingClientPort;
    }
}

// P2P服务器
class P2PServer {
    private int serverPort;
    private List<SharedFile> sharedFiles;

    public P2PServer(int serverPort) {
        this.serverPort = serverPort;
        this.sharedFiles = new ArrayList<>();
    }

    public void start() {
        try (ServerSocket serverSocket = new ServerSocket(serverPort)) {
            System.out.println("P2P服务器已启动，监听端口：" + serverPort);

            while (true) {
                Socket clientSocket = serverSocket.accept();
                new ClientHandler(clientSocket).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private class ClientHandler extends Thread {
        private Socket clientSocket;

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

        public void run() {
            try (ObjectInputStream in = new ObjectInputStream(clientSocket.getInputStream());
                 ObjectOutputStream out = new ObjectOutputStream(clientSocket.getOutputStream())) {

                // 接收客户端的共享文件列表
                List<SharedFile> clientSharedFiles = (List<SharedFile>) in.readObject();

                // 将客户端的共享文件列表合并到服务器的列表中
                sharedFiles.addAll(clientSharedFiles);

               // 处理下载请求
                while (true) {
                    DownloadRequest request = (DownloadRequest) in.readObject();
                    if (request != null) {
                        out.writeObject(request);
                    }
                }

            } catch (IOException | ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        // 启动P2P服务器
        P2PServer server = new P2PServer(12345);
        server.start();

        // 启动P2P客户端并共享文件
        P2PClient client = new P2PClient("localhost", 12345);
        client.addSharedFile("sharedfile.txt");
        client.start();
    }
}