FTP 220 Service Ready vs 425 Can't Open Data Connection
FTP 220 (Service Ready) is a 2xx Positive Completion response, while 425 (Can't Open Data Connection) is a 4xx Transient Negative response. 220 indicates that service ready for new user. This is the greeting message sent by the FTP server when a client first connects. In contrast, 425 means that can't open data connection. The server was unable to establish the data channel needed for the file transfer.
描述
Service ready for new user. This is the greeting message sent by the FTP server when a client first connects.
何时出现
Immediately upon connecting to an FTP server. This is the welcome banner confirming the server is accepting connections.
如何修复
No fix needed — the server is ready. Proceed with USER and PASS commands to authenticate.
描述
Can't open data connection. The server was unable to establish the data channel needed for the file transfer.
何时出现
When a firewall or NAT is blocking the data connection, or the client failed to connect to the server's passive port.
如何修复
Switch between active (PORT) and passive (PASV) modes. Check that your firewall allows the FTP data port range and that NAT is configured correctly.
主要区别
220 is a 2xx Positive Completion response, while 425 is a 4xx Transient Negative response.
FTP 220: Service ready for new user. This is the greeting message sent by the FTP server when a client first connects.
FTP 425: Can't open data connection. The server was unable to establish the data channel needed for the file transfer.
You encounter 220 when immediately upon connecting to an FTP server. This is the welcome banner confirming the server is accepting connections.
You encounter 425 when when a firewall or NAT is blocking the data connection, or the client failed to connect to the server's passive port.
何时使用哪个
For 220 (Service Ready): No fix needed — the server is ready. Proceed with USER and PASS commands to authenticate. For 425 (Can't Open Data Connection): Switch between active (PORT) and passive (PASV) modes. Check that your firewall allows the FTP data port range and that NAT is configured correctly.