| Code | Description |
| 100 Series | The requested action is being initiated, expect another reply before proceeding with a new command. |
| 110 | Restart marker reply. |
| 120 | Service ready in nn minutes. |
| 125 | Data Connection already open, transfer starting. |
| 150 | File status okay, about to open data connection. |
| 200 Series | The requested action has been successfully completed. |
| 200 | Command okay. |
| 202 | Command not implemented, superfluous at this site. |
| 211 | System status, or system help reply. |
| 212 | Directory status. |
| 213 | File status. |
| 214 | Help message. |
| 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. |
| 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 (for example – file transfer or file abort). |
| 227 | Entering Passive Mode. |
| 230 | User logged in, proceed. |
| 250 | Requested file action okay, completed. |
| 257 | „PATHNAME“ created. |
| 300 Series | The command has been accepted, but the requested action is on hold, pending receipt of further information. |
| 331 | User name okay, need password. |
| 332 | Need account for login. |
| 350 | Requested file action pending further information. |
| 400 Series | 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. |
| 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. Try changing from PASV to PORT mode. |
| 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 Series | The command was not accepted and the requested action did not take place. |
| 501 | Syntax error in parameters or arguments. |
| 502 | Command not implemented. |
| 503 | Bad sequence of commands. |
| 504 | Command not implemented for that parameter. |
| 530 | Not logged in. Your password is being rejected, contact the server administrator. |
| 532 | Need account for storing files. |
| 550 | Requested action not taken. File unavailable (e.g., file not found, no access). Contact the server administrator. |
| 552 | Requested file action aborted. Exceeded storage allocation (for current directory or data set). Contact the server administrator. |
| 553 | Requested action not taken. File name not allowed. Try changing the file name, or getting rid of spaces in the file name. |
| 10000 series | Winsock error codes |
| 10054 | Connection Reset by Peer – The connection was forcibly closed by the remote host. |
| 10060 | Can’t connect to remote server (Generally a time-out error). Try switching from PASV to PORT mode. |
| 10061 | Can’t connect to remote server. The connection is actively refused by the server. Try switching from PASV to PORT mode. |
| 10066 | Directory not empty. The server will not delete this directory while there are files/folders in it. |
| 10068 | Too many users, server is full. Contact the server administrator. |