File Transfer Protocol (FTP)
Whereas Telnet facilitates a live connection to the remote host, FTP is more passive, allowing you to move files back and forth from remotely located servers. This utility is ideal for Webmasters or anyone requiring to move large files from one location to another with no previously established "hot" connection. FTP is typically operated in what is called Passive Mode, which loads directory trees to the client and then disconnects, but periodically "tickles" the server to maintain an open port.
Various FTP servers will be configured based on the particular Webmaster's tastes. Some allow anonymous users to access all areas of the server without restriction. Others limit access to previously authenticated users only. Still others limit anonymous access to very short timeout periods. If the user is not active, the server automatically disconnects, forcing him to reconnect if he wants to continue using the server.
On Unix-based systems, these programs are typically named ftpd (again, "d" meaning daemon) and ftp (the client application). FTP's default ports are 20 (for data transfers) and 21 (for command transfers). This makes FTP unique among TCP/IP protocols because commands and data can be transferred simultaneously with the data being transferred in real time, a feature that other protocols do not share.
All operating systems have FTP clients and servers in one form or another. All MacOS-based FTP applications are graphically oriented. Most Windows-based ones now are as well. The benefits to using a graphical FTP client is that all the commands, usually entered by hand, are now managed by the client, reducing the possibility of error and making sessions quicker and easier. On the other hand, because FTP servers do not require much management after the initial setup, they don't require a GUI.