The server replies to individual FTP protocol commands set by the client with a message with a three-digit return code followed by text clarifying the return code. The three-digit return code has the form xyz where:
x takes any of these following values:
- 1: A positive preliminary reply when starting some action. Before the client can send another command, one can expect a message about the termination of the action.
- 2: A positive completion reply (the requested action has been successfully completed). The client can send commands.
- 3: A positive immediate reply after which the client has to perform a concrete action. For instance, after entering a username, a password is required.
- 4: A transient negative completion reply. This means the command was not accepted and the requested action did not take place, but the error condition is temporary and the action may be requested again.
- 5: A permanent negative completion reply, for example, on an unsupported command.
y can take any...