FTP 211 System Status vs 421 Service Not Available
FTP 211 (System Status) is a 2xx Positive Completion response, while 421 (Service Not Available) is a 4xx Transient Negative response. 211 indicates that system status or system help reply. The server provides information about its current status or available features. In contrast, 421 means that service not available, closing control connection. The server is shutting down or has reached its connection limit and cannot serve this request.
説明
System status or system help reply. The server provides information about its current status or available features.
このコードが表示される場合
After issuing the STAT command without arguments, the server returns its system status and supported features.
解決方法
No fix needed — this is an informational response. Use the information to understand the server's capabilities and current state.
説明
Service not available, closing control connection. The server is shutting down or has reached its connection limit and cannot serve this request.
このコードが表示される場合
When the FTP server is overloaded, shutting down for maintenance, or has reached its maximum number of concurrent connections.
解決方法
Wait a few minutes and try reconnecting. If persistent, check if the server has a connection limit and whether your IP is being rate-limited.
主な違い
211 is a 2xx Positive Completion response, while 421 is a 4xx Transient Negative response.
FTP 211: System status or system help reply. The server provides information about its current status or available features.
FTP 421: Service not available, closing control connection. The server is shutting down or has reached its connection limit and cannot serve this request.
You encounter 211 when after issuing the STAT command without arguments, the server returns its system status and supported features.
You encounter 421 when when the FTP server is overloaded, shutting down for maintenance, or has reached its maximum number of concurrent connections.
どちらをいつ使うか
For 211 (System Status): No fix needed — this is an informational response. Use the information to understand the server's capabilities and current state. For 421 (Service Not Available): Wait a few minutes and try reconnecting. If persistent, check if the server has a connection limit and whether your IP is being rate-limited.