FTP 110 Restart Marker Reply vs 503 Bad Sequence
FTP 110 (Restart Marker Reply) is a 1xx Positive Preliminary response, while 503 (Bad Sequence) 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, 503 means that bad sequence of commands. The command is valid but was sent in the wrong order relative to other commands.
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
Bad sequence of commands. The command is valid but was sent in the wrong order relative to other commands.
When You See It
When you skip a required step, like sending PASS before USER, or RNTO without first sending RNFR.
How to Fix
Follow the correct command sequence. Common sequences: USER then PASS for login, RNFR then RNTO for rename, PASV then RETR for transfer.
Key Differences
110 is a 1xx Positive Preliminary response, while 503 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 503: Bad sequence of commands. The command is valid but was sent in the wrong order relative to other commands.
You encounter 110 when during a resumed file transfer when the server confirms the restart position in the data stream.
You encounter 503 when when you skip a required step, like sending PASS before USER, or RNTO without first sending RNFR.
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 503 (Bad Sequence): Follow the correct command sequence. Common sequences: USER then PASS for login, RNFR then RNTO for rename, PASV then RETR for transfer.