FTP 110 Restart Marker Reply vs 502 Command Not Implemented
FTP 110 (Restart Marker Reply) is a 1xx Positive Preliminary response, while 502 (Command Not Implemented) is a 5xx Permanent Negative response. 110 indicates that the server is sending a restart marker reply. The text is exact and not left to interpretation. This marker is used to indicate the point at which a file transfer should be restarted. In contrast, 502 means that command not implemented. The server recognizes the command but does not support it in its current configuration.
Description
The server is sending a restart marker reply. The text is exact and not left to interpretation. This marker is used to indicate the point at which a file transfer should be restarted.
When You See It
During a resumed file transfer when the server confirms the restart position in the data stream.
How to Fix
No fix needed — this is a normal response during transfer recovery. If restarts keep failing, verify the marker format matches what your client expects.
Description
Command not implemented. The server recognizes the command but does not support it in its current configuration.
When You See It
When you use a valid FTP command that this particular server has not implemented, such as SITE or SMNT.
How to Fix
Use an alternative command or approach. Check the server's FEAT response or HELP output to see which commands are actually supported.
Key Differences
110 is a 1xx Positive Preliminary response, while 502 is a 5xx Permanent Negative response.
FTP 110: The server is sending a restart marker reply. The text is exact and not left to interpretation. This marker is used to indicate the point at which a file transfer should be restarted.
FTP 502: Command not implemented. The server recognizes the command but does not support it in its current configuration.
You encounter 110 when during a resumed file transfer when the server confirms the restart position in the data stream.
You encounter 502 when when you use a valid FTP command that this particular server has not implemented, such as SITE or SMNT.
When to Use Which
For 110 (Restart Marker Reply): No fix needed — this is a normal response during transfer recovery. If restarts keep failing, verify the marker format matches what your client expects. For 502 (Command Not Implemented): Use an alternative command or approach. Check the server's FEAT response or HELP output to see which commands are actually supported.