The File Transfer Protocol FTP is the primary Internet standard for file transfer. The current specification is contained in RFC-959 [FTP:1].
FTP uses separate simultaneous TCP connections for control and for data transfer. The FTP protocol includes many features, some of which are not commonly implemented. However, for every feature in FTP, there exists at least one implementation. The minimum implementation defined in RFC-959 was too small, so a somewhat larger minimum implementation is defined here.
Internet users have been unnecessarily burdened for years by deficient FTP implementations. Protocol implementors have suffered from the erroneous opinion that implementing FTP ought to be a small and trivial task. This is wrong, because FTP has a user interface, because it has to deal (correctly) with the whole variety of communication and operating system errors that may occur, and because it has to handle the great diversity of real file systems in the world.