passive mode. It means that the FTP client
opens data connection by connecting to the supplied port on the FTP server. Otherwise, data
connections are opened in the active mode. It means that the data connection is opened by
the FTP server by connecting to the supplied port on the FTP client. This mode is problematic
if the FTP client is behind firewall or proxy server because they can block access to the FTP
client (if they have not support for FTP protocol). The passive mode is not supported by some
FTP s