UseExtensionDataPort is a Boolean property used to indicate if IPv6 extensions for Port and Passive settings should be used in FTP protocol exchanges. The UseExtensionDataPort property prevents the FTP client from sending IPv6 values in the FTP PORT and PASV commands, which cannot handle the IPv6 address format. 

The default value for UseExtensionDataPort is DEF_Id_TIdFTP_UseExtendedData, as assigned during initialization of the component. 

Changing the value in the UseExtensionDataPort property to False while IPVersion contains the value IPv6 will result in an EIdFTPMustUseExtWithIPv6 exception being raised. 

Changing the value in the UseExtensionDataPort property to False while TryNATFastTrack returns True will result in an EIdFTPMustUseExtWithNATFastTrack exception being raised. 

UseExtensionDataPort will be set to True when a socket-based IOHandler is assigned for the FTP client (in the control channel) that uses the value Id_IPv6 in its IPVersion property. 

Use the value in UsingExtDataPort to determine if the IPv6 extensions are valid after performing FTP protocol exchanges that might alter support for the capability.

Port 

IOHandler 

Connect