FTP连接超时421：解析器错误

Question

这个问题已被编辑。我试图列出FTP目录中的所有文件 - 虽然代码在正常的Netbeans项目中运行时工作正常，但在Maven项目中使用相同的代码时会导致连接超时421 。我怎么能摆脱这个？

代码：

FTPClient ftpClient = new FTPClient();
ftpClient.connect(host, 21);
ftpClient.login(user, pass);
ftpClient.enterLocalPassiveMode();
ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
FTPClientConfig conf = new FTPClientConfig(FTPClientConfig.SYST_UNIX);
ftpClient.configure(conf);
inputStream = FTPUtil.downloadSingleFile(ftpClient, filePath);
ftpClient.list();                         // It works
ftpClient.listNames("/");                 // It works
ftpClient.changeWorkingDirectory("/");    // It works
FTPFile[] files = ftpClient.listFiles("/");// It hangs and stops 421 connection timed out

FileZilla日志是： -

    (000370)04-04-2013 16:04:32 - (not logged in) (127.0.0.1)> Connected, sending welcome message...
    (000370)04-04-2013 16:04:32 - (not logged in) (127.0.0.1)> 220 ftp connection started...
    (000370)04-04-2013 16:04:32 - (not logged in) (127.0.0.1)> USER raja
    (000370)04-04-2013 16:04:32 - (not logged in) (127.0.0.1)> 331 Password required for raja
    (000370)04-04-2013 16:04:32 - (not logged in) (127.0.0.1)> PASS ****
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> 230 Logged on
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> TYPE I
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> 200 Type set to I
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> PASV
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> 227 Entering Passive Mode (127,0,0,1,237,187)
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> SYST
    (000370)04-04-2013 16:04:32 - raja (127.0.0.1)> 215 UNIX emulated by FileZilla
    (000366)04-04-2013 16:04:33 - raja (127.0.0.1)> 421 Connection timed out.

客户方例外情况如下： -

Answer 1

当FTP服务器针对 SYST 命令返回 null 时，apache-commons 1.4.1在处理解析异常时存在严重问题。我尝试使用版本3.2，问题得到解决。