Most Common FTP errors

Code	Description
100 Codes	The requested action is being taken. Expect a reply before proceeding with a new command.
110	Restart marker reply.
120	Service ready in (n) minutes.
125	Data connection already open, transfer starting.
150	File status okay, about to open data connection.
200 Codes	The requested action has been successfully completed.
200	Command okay.
202	Command not implemented
211	System status, or system help reply.
212	Directory status.
213	File status.
214	Help message.
215	NAME system type. (NAME is an official system name from the list in the Assigned Numbers document.)
220	Service ready for new user.
221	Service closing control connection. (Logged out if appropriate.)
225	Data connection open, no transfer in progress.
226	Closing data connection. Requested file action successful (file transfer, abort, etc.).
227	Entering Passive Mode
230	User logged in, proceed.
250	Requested file action okay, completed.
257	"PATHNAME" created.
300 Codes	The command has been accepted, but the requested action is being held pending receipt of further information.
331	User name okay, need password.
332	Need account for login.
350	Requested file action pending further information.
400 Codes	The command was not accepted and the requested action did not take place. The error condition is temporary, however, and the action may be requested again.
421	Service not available, closing control connection. (May be a reply to any command if the service knows it must shut down.)`
425	Can't open data connection.
426	Connection closed, transfer aborted.
450	Requested file action not taken. File unavailable (e.g., file busy).
451	Requested action aborted, local error in processing.
452	Requested action not taken. Insufficient storage space in system.
500 Codes	The command was not accepted and the requested action did not take place.
500	Syntax error, command unrecognized. This may include errors such as command line too long.
501	Syntax error in parameters or arguments.
502	Command not implemented.
503	Bad sequence of commands.
504	Command not implemented for that parameter.
530	User not logged in.
532	Need account for storing files.
550	Requested action not taken. File unavailable (e.g., file not found, no access).
552	Requested file action aborted, storage allocation exceeded
553	Requested action not taken. Illegal file name.

http://www.theegglestongroup.com/writing/ftp_error_codes.php