Docker Environment Operating FTP error: FTP response 421 received.Server closed connection resolved

Recent projects in Docker slowly transition to the environment, was found on a very stable place to upload files to FTP server error in the testing process, mainly the following error message:

FTP response 421 received.Server closed connection

After find a solution was found when uploading FTP, FTP operations only need to be changed to passive mode (ftpClient.enterLocalPassiveMode ();), redeploy test FTP upload files to normal after the modification.
Examples are as follows:

@Component
public class FtpUtils {

    private static Logger logger = LoggerFactory.getLogger(UserLoginController.class);

    @Autowired
    private FtpConfig ftpConfig;

    public FTPClient ftpClient = null;

    /**
     * 初始化链接文件
     */
    public void initFtpClient() {
        ftpClient = new FTPClient();
        ftpClient.setRemoteVerificationEnabled(false);                                  //取消服务器获取自身Ip地址和提交的host进行匹配，否则当不一致时会报异常。
        ftpClient.setControlEncoding("utf-8");                                          //在连接之前设置编码类型为utf-8
        try {
            ftpClient.setDataTimeout(1000*120);                                         //设置传输超时时间为120秒
            ftpClient.connect(ftpConfig.getHostname(), ftpConfig.getPort());            //连接ftp服务器
            ftpClient.login(ftpConfig.getUsername(), ftpConfig.getPassword());          //登录ftp服务器
            int replyCode = ftpClient.getReplyCode();                                   //是否成功登录服务器

            if(!FTPReply.isPositiveCompletion(replyCode)){
                logger.warn("【initFtpClient】: 登录服务器失败");
            }            
            logger.warn("【initFtpClient】: 使用帐户："+ftpConfig.getUsername()+"密码："+ftpConfig.getPassword()+"登录ftp服务器："+ftpConfig.getHostname()+":"+ftpConfig.getPort());
            logger.warn("【initFtpClient】: 成功登录服务器,被动模式主机："+ftpClient.getPassiveHost()+":"+ftpClient.getPassivePort());
            logger.warn("【initFtpClient】: 成功登录服务器,主动模式主机："+ftpClient.getRemoteAddress()+":"+ftpClient.getRemotePort());
            logger.warn("【initFtpClient】: 成功登录服务器,本地主机："+ftpClient.getLocalAddress()+":"+ftpClient.getLocalPort());
            logger.warn("【initFtpClient】: 成功登录服务器,返回代码："+ftpClient.getReplyCode()+",显示状态"+ftpClient.getStatus());           

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


    /**
     * 上传文件
     * @param pathname ftp服务保存地址
     * @param fileName 上传到ftp的文件名
     * @param inputStream 输入文件流
     * @return
     */
    public boolean uploadFile( String pathname, String fileName,InputStream inputStream){
        boolean flag = false;
        try{
            logger.warn("【uploadFile】: " + "开始上传文件");
            initFtpClient();
            ftpClient.setFileType(ftpClient.BINARY_FILE_TYPE);  //设置传输的模式为二进制文件类型传输
            ftpClient.makeDirectory(pathname);                      //设置目录
            ftpClient.changeWorkingDirectory(pathname);             //设置工作路径

            ftpClient.enterLocalPassiveMode();                      //设置被动模式(FTP客户端在docker容器内，需用被动模式)
            ftpClient.storeFile(fileName, inputStream);             //上传

            logger.warn("【uploadFile】: " + "上传文件成功");
            flag = true;            
            return flag;
        }catch (Exception e) {
            logger.warn("【uploadFile】: " + "上传文件失败");
            e.printStackTrace();
            return flag;
        }finally{
            if(null != inputStream){
                try {
                    inputStream.close();                            //关闭文件流
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(ftpClient.isConnected()){
                try{

                    ftpClient.logout();                             //退出FTP
                    ftpClient.disconnect();                         //断开连接
                }catch(IOException e){
                    e.printStackTrace();
                }
            }
        }
    }



}