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The FTP server prefixes all replies with a 3-digit "reply code". For example, the very first reply looks something like:
220 gemini Microsoft FTP Service (Version 2.0).
This is a response to a user connecting to the server. The digits within the code have specific meaning. The first digit is a general status of the command, the second digit is the function of the command, and the third digit gives finer interpretation. That first reply code of "220" indicates that the status is "success" and that the reply code is related to the "connection". Many other protocols such as SMTP, POP, and HTTP have adopted the FTP reply code scheme. The first digit of a reply code indicates the general status of the command. These are: - 1xx
- A "preliminary" reply: the server has not yet completed the command, another reply code should be expected.
- 2xx
- A "positive" reply: the command has been completed successfully. The most common version of this is simply "200".
- 3xx
- Not quite as "positive" as a 2xx reply. This indicates that some "intermediate" error has occurred, and that the user should revise the request and resend it.
- 4xx
- The request failed. This could be a simple reason like the file not being found.
- 5xx
- Permanent failure. A sever error occurred; this command will never succeed.
The second digit of the reply code has the following interpretations: - x0x - Syntax
- The request was malformed in some fashion; maybe the user mistyped a command.
- x1x - Information
- Replies to status and help commands.
- x2x - Connections
- The reply is related to the status of the connection.
- x3x - Authentication and accounting
- For example, when you enter a username, the reply code is "331", where the first digit 3 indicates that status that more information is required, and the second 3 indicates that authentication information is the type of information. If you enter a bad password, the status code is "530", where the first digit 5 indicates a failure, and the second digit 3 indicates that the failure was due to authentication.
- x4x - Unspecified
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- x5x - File
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Some example reply codes: - 110 Restart marker reply.
- In this case, the text is exact and not left to the particular implementation; it must read: MARK yyyy = mmmm Where yyyy is User-process data stream marker, and mmmm server's equivalent marker (note the spaces between markers and "=").
- 120 Service ready in nnn minutes.
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- 125 Data connection already open; transfer starting.
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- 150 File status okay; about to open data connection.
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- 200 Command okay.
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- 202 Command not implemented, superfluous at this site.
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- 211 System status, or system help reply.
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- 212 Directory status.
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- 213 File status.
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- 214 Help message.
- On how to use the server or the meaning of a particular non-standard command. This reply is useful only to the human user.
- 215 NAME system type.
- Where NAME is an official system name from the list in the Assigned Numbers document.
- 220 Service ready for new user.
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- 221 Service closing control connection.
- Logged out if appropriate.
- 225 Data connection open; no transfer in progress.
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- 226 Closing data connection.
- Requested file action successful (for example, file transfer or file abort).
- 227 Entering Passive Mode (h1,h2,h3,h4,p1,p2).
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- 230 User logged in, proceed.
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- 250 Requested file action okay, completed.
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- 257 "PATHNAME" created.
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- 331 User name okay, need password.
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- 332 Need account for login.
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- 350 Requested file action pending further information.
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- 421 Service not available, closing control connection.
- This may be a reply to any command if the service knows it must shut down.
- 425 Can't open data connection.
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- 426 Connection closed; transfer aborted.
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- 450 Requested file action not taken.
- File unavailable (e.g., file busy).
- 451 Requested action aborted: local error in processing.
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- 452 Requested action not taken.
- Insufficient storage space in system.
- 500 Syntax error, command unrecognized.
- This may include errors such as command line too long.
- 501 Syntax error in parameters or arguments.
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- 502 Command not implemented.
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- 503 Bad sequence of commands.
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- 504 Command not implemented for that parameter.
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- 530 Not logged in.
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- 532 Need account for storing files.
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- 550 Requested action not taken.
- File unavailable (e.g., file not found, no access).
- 551 Requested action aborted: page type unknown.
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- 552 Requested file action aborted.
- Exceeded storage allocation (for current directory or dataset).
- 553 Requested action not taken.
- File name not allowed.
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