How to enable UPnP support?

I am current using a LinkSys Router that supports UPnP. and i have already enabled UPnP in router settings. My OS is WindowsXP.
However, smartFTP do not use the UPnP service to connect to an FTP that is behind a router. How can I enable UPnP support in smartFTP? Is there any things that I need to do on my windows before i can enable UPnP support?

UPnP is only functional in the "Active Mode" state. Default 21 FTP servers are excluded as well.
UPnP is automatically activated upon, right before the "PORT" command is sent to the FTP server.
Also make sure that the "Port IP Mode" option is set to "Auto", which is the default when installed.
Tools > Settings > Connection -> "Data Connection".

Please also take a moment to view the UPnP article.
https://www.smartftp.com/support/kb/174

I also recommend the "Active vs Passive" mode article.
https://www.smartftp.com/support/kb/2

And last, here is an example of UPnP taking place:

[15:27:42] UPNP: Added Port Mapping: Router:40413 -> 10.10.10.10:40413
[15:27:42] UPNP: GetExternalIPAddress returned: "195.141.90.6"
[15:27:42] PORT 195,141,90,6,157,221
[15:27:42] 200 Port command ok.
[15:27:42] Opening data connection IP: 195.141.90.6 PORT: 40413.
[15:27:42] LIST -aL
[15:27:42] 150 Opening ASCII data connection for ls /.
[15:27:43] 755 bytes received successfully. (755 B/s) (00:00:01).
[15:27:43] UPNP: Removed Port Mapping: Router:40413
[15:27:44] 226 Transfer finished successfully. Data connection closed .!

Do I understand you correctly that uPnP doesn't work on port 21?

Will it still be able to connect to port 21 on the other end? I'm wrestling my damn router every day, and of course this is another in the endless line of problems I'm having where it takes days to figure out if it's software settings, router settings or lack of router functionality that's torturing me.