FTP 125 Data Connection Open vs 451 Local Error
FTP 125 (Data Connection Open) is a 1xx Positive Preliminary response, while 451 (Local Error) is a 4xx Transient Negative response. 125 indicates that the data connection is already open and the transfer is beginning. No need to open a new data connection. In contrast, 451 means that requested action aborted: local error in processing. The server encountered an unexpected error while trying to complete the command.
Description
The data connection is already open and the transfer is beginning. No need to open a new data connection.
When You See It
When the server reuses an existing data connection for a file transfer instead of opening a new one.
How to Fix
No fix needed — the transfer is starting immediately. Your client should begin reading or writing data on the existing connection.
Description
Requested action aborted: local error in processing. The server encountered an unexpected error while trying to complete the command.
When You See It
When the server has an internal issue like a disk I/O error, memory shortage, or filesystem problem during command processing.
How to Fix
Retry the command. If the error persists, contact the server administrator to check disk health, available memory, and server logs.
Key Differences
125 is a 1xx Positive Preliminary response, while 451 is a 4xx Transient Negative response.
FTP 125: The data connection is already open and the transfer is beginning. No need to open a new data connection.
FTP 451: Requested action aborted: local error in processing. The server encountered an unexpected error while trying to complete the command.
You encounter 125 when when the server reuses an existing data connection for a file transfer instead of opening a new one.
You encounter 451 when when the server has an internal issue like a disk I/O error, memory shortage, or filesystem problem during command processing.
When to Use Which
For 125 (Data Connection Open): No fix needed — the transfer is starting immediately. Your client should begin reading or writing data on the existing connection. For 451 (Local Error): Retry the command. If the error persists, contact the server administrator to check disk health, available memory, and server logs.