Java使用Socket基于TCP实现简单FTP上传文件和下载文件功能

上传端/客户端

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


public class Client {
    // 定义本机端口的地址。因为是在本机，所以将端口和地址定义成静态的常量
    private static final String HOST = "localhost";
    private static final int PORT = 1721;

    /**
     * @param fileName 上传的文件的路径和文件名
     */
    public void upFile(String fileName) {
        try {
            Socket socket = new Socket(HOST, PORT);
            File file = new File(fileName);
            System.out.println("文件长度:" + (int) file.length());
            DataInputStream fileIn = new DataInputStream(new FileInputStream(fileName));
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
            byte[] buf = new byte[1024];
            while ((fileIn.read(buf))!=-1) {
                out.write(buf, 0, buf.length);
            }
            out.flush();
            fileIn.close();
            out.close();
            socket.close();
            System.out.println("文件传输完成");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        Client client = new Client();
        client.upFile("src\\test.txt");//需要上传的文件的位置，请根据需要更改
    }
}

下载端/服务端

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    private static final int PORT=1721;
    /**
     *
     * @param fileName 下载的文件保存路径和文件名
     */
    public void downFile(String fileName) {
        try {
            ServerSocket serverSocket = new ServerSocket(PORT);
            Socket socket = serverSocket.accept();
            System.out.println("建立socket链接");
            DataInputStream inputStream = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
            byte[] buf = new byte[1024];
            DataOutputStream fileOut = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(fileName)));
            System.out.println("开始接收文件!" + "\n");
            while ((inputStream.read(buf))!=-1) {
                fileOut.write(buf, 0,buf.length);
            }
            System.out.println("接收完成，文件存为" + fileName);
            fileOut.close();
        } catch (Exception e) {
            System.out.println("接收消息错误");
            e.printStackTrace();
            return;
        }
    }

    public static void main(String[] args) {
        Server server=new Server();
        server.downFile("src\\copy.txt");//下载的文件想要存放的的位置和文件名，请根据需要更改
    }

}