The File Transfer Protocol (FTP) is a standard network protocol used to transfer computer files from one host to another host over a TCP-based network, such as the Internet.
FTP is built on a client-server architecture and uses separate control and data connections between the client and the server
FTP Reply Codes:-
2yz – Success reply
4yz or 5yz – Failure reply
1yz or 3yz – Error or Incomplete reply
x0z – Syntax. These replies refer to syntax errors.
x1z – Information. Replies to requests for information.
x2z – Connections. Replies referring to the control and data connections.
x3z – Authentication and accounting. Replies for the login process and accounting procedures.
x4z – Not defined.
x5z – File system. These replies relay status codes from the server file system.