题目

需求：
使用tcp协议，编写客户端（有一个专门存放下载文件的目录files）和服务端（有一个专门存放资源的download目录）：

• 当客户端给服务端发送 “list”命令时，服务端给客户端响应download文件夹下所有的文件名称，客户端需要把接收到的文件名称打印到控制台
• 当客户端给服务端发送 “服务端download文件夹下的文件名称” 命令时，服务端给客户端响应 download文件夹下对应的文件内容，客户端要把接受到的文件存储到 files 文件夹下
• 服务端和客户端的通信需要在子线程中完成
• 客户端给服务端发送一个命令，服务端给客户端响应一些内容，看做是一个流程，当这个流程完毕后，通信双方的socket都需要关闭，释放资源。

作答

ClientDemo.java

import java.io.*;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Scanner;

public class ClientDemo {
    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);

        Socket socket = new Socket("127.0.0.1", 10000);
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(socket.getOutputStream());
        int count = 0;
        while (!scanner.nextLine().equals("list")){
            System.out.println("命令无效！");
            if (++count == 10){
                System.exit(0);
            }
        }
        bufferedOutputStream.write("list".getBytes());
        socket.shutdownOutput();


        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        ArrayList<String> list = new ArrayList<>();
        String s;
        while ((s = bufferedReader.readLine()) != null){
            list.add(s);
        }
        bufferedReader.close();
        bufferedOutputStream.close();


        io:while (true){
            String inputChoices = scanner.next();
            boolean flag = false;
            for (String s1 : list) {
                if (inputChoices.equals(s1)){
                    BufferedOutputStream bufferedOutputStream1 = new BufferedOutputStream(socket.getOutputStream());
                    bufferedOutputStream1.write(s1.getBytes());
                    flag = true;
                    break io;

                }
            }
            if (!flag){
                System.out.println("未找到输入的文件！");
            }
        }
        BufferedInputStream bufferedInputStream = new BufferedInputStream(socket.getInputStream());
        BufferedOutputStream bufferedOutputStream1 = new BufferedOutputStream(new FileOutputStream("C:\\Users\\Ensio\\Desktop\\HeiMa\\题库(2)\\题库\\robin\\files\\"));

        socket.close();
    }
}

ServerDemo.java

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class ServerDemo {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(10000);
        Socket accept = serverSocket.accept();
        BufferedInputStream bufferedInputStream = new BufferedInputStream(accept.getInputStream());
        String str = readClient(bufferedInputStream);
        //  C:\Users\Ensio\Desktop\HeiMa\题库(2)\题库\robin\download
        File file = new File("C:\\Users\\Ensio\\Desktop\\HeiMa\\题库(2)\\题库\\robin\\download");
        ArrayList<String> list = new ArrayList<>();
        if ("list".equals(str)) {

            BufferedWriter bufferedOutputStream = new BufferedWriter(new OutputStreamWriter(accept.getOutputStream()));
            writeFile(file, list, bufferedOutputStream);
        }

        BufferedInputStream bufferedInputStream1 = new BufferedInputStream(accept.getInputStream());
        String fileName = readClient(bufferedInputStream1);

        String filePath = findFilePath(fileName, file);
        BufferedOutputStream bufferedOutputStream2 = new BufferedOutputStream(accept.getOutputStream());

        BufferedInputStream bufferedInputStream2 = new BufferedInputStream(new FileInputStream(filePath));
        int len;
        while ((len = bufferedInputStream2.read()) != -1){
            bufferedOutputStream2.write(len);
        }


        bufferedInputStream.close();
        bufferedInputStream1.close();
        bufferedInputStream2.close();
        bufferedOutputStream2.close();
        serverSocket.close();

    }
    public static String findFilePath(String s, File file){
        File[] files = file.listFiles();
        String s1 = "";
        for (File file1 : files) {
            if (file1.isFile()){
                if (file1.getName().equals(s)){
                    s1 += file1;
                }
            }else {
                findFilePath(s,file1);
            }
        }
        return s1;
    }
    public static String readClient(BufferedInputStream bufferedInputStream) throws IOException {
        byte[] bytes = new byte[1024];
        int len;
        String str = null;
        while ((len = bufferedInputStream.read(bytes)) != -1){
            str += new String(bytes, 0, len);
        }
        return str;
    }
    public static ArrayList<String> filePathToClient(File file, ArrayList<String> list){

        File[] files = file.listFiles();
        for (File file1 : files) {

            if (file1.isDirectory()){
                filePathToClient(file1 , list);
            }else {
                list.add(file1.getName());
            }
        }
        return list;
    }
    public static void writeFile(File file, ArrayList<String> list, BufferedWriter bufferedOutputStream) throws IOException {
        if (file.exists()){
            list = filePathToClient(file, list);
            for (String s : list) {
                bufferedOutputStream.write(s);
                bufferedOutputStream.newLine();
            }
            bufferedOutputStream.flush();
            bufferedOutputStream.close();
        }else {
            bufferedOutputStream.write("空文件夹！");
        }

    }
}