When a client experiences problems when connecting to your FTP server, one thing you might want to look into is whether you've set your FTP data transfer mode to either active or passive. Active and passive are two possible modes that an FTP connection can operate on. Taking into consideration the network configurations and security controls in place, you should choose one mode over the other. But before we discuss which mode is best for what scenario, let's first talk about the basics of these two modes, which can best be explained if we start our discussion with the two channels an FTP session normally has. FTP command channel and data channel A typical FTP session operates using two channels: a command (or control) channel and a data channel. As their names imply, the command channel is used for transmitting commands as well as replies to those commands, while the data channel is used for transferring data. Unless you configure your FTP server diffe