FTP server return codes show their status by the digits within them. A short explanation of various digits’ meanings are given below:

• 1xx: Positive Preliminary reply. The action requested is being initiated but there will be another reply before it begins.
• 2xx: Positive Completion reply. The action requested has been completed. The client may now issue a new command.
• 3xx: Positive Intermediate reply. The command was successful, but a further command is required before the server can act upon the request.
• 4xx: Transient Negative Completion reply. The command was not successful, but the client is free to try the command again as the failure is only temporary.
• 5xx: Permanent Negative Completion reply. The command was not successful and the client should not attempt to repeat it again.
• x0x: The failure was due to a syntax error.
• x1x: This response is a reply to a request for information.
• x2x: This response is a reply relating to connection information.
• x3x: This response is a reply relating to accounting and authorization.
• x4x: Not used.
• x5x: These responses indicate the status of the Server file system vis-a-vis the requested transfer or other file system action.