FTP Active Passive

What is the difference between Active and Passive Modes?

FTP involves two computers communicating with one another. The two computers are a client (your PC) and a server (the computer where your website is stored). This communication involves sending commands (i.e. when the two computers ‘talk’ to each other) and sending data (when pages or pictures are being transmitted). Passive FTP is when the client is responsible for controlling the sending of commands and for the sending of data, while the server does nothing i.e. the server remains passive. With active FTP the server is not passive and takes a more ‘active’ part in the FTP process.

Active FTP may cause problems if your client is behind a firewall. This is because, from the firewall’s point of view, when the server is active it looks like an intruder and is usually blocked. This is why many users have difficulty using FTP from behind a firewall. Setting your FTP software to use Passive FTP solves this problem.