FTP Error 425 Data Connection Failure

FTP error 425 occurs when the client is unable to establish the data connection required for file transfers. This is typically caused by firewall restrictions or incorrect passive/active mode configuration in FTP communication.

FTP uses two separate connections: one control connection for commands and another data connection for transferring files. Error 425 usually indicates that the data connection could not be established, often due to firewall rules blocking incoming or outgoing connections.

Most modern FTP components (such as IPWorks FTP / FTPS) use passive mode by default, where the client initiates both connections. In passive mode (Passive = true), the server provides a port for data transfer, which must be allowed through firewalls.

Switching between passive and active mode may help depending on network configuration, as active mode requires the server to initiate the data connection back to the client.

The issue is typically resolved by ensuring correct firewall configuration and adjusting the Passive property based on the environment.