Thanks for replying. I couldn't see any free service at dyndns.org. But is the router IP addr the external IP? I can see that on my router setup, and also when I run speedtest.net, the same IP addr shows.
On my router, I've attached a jpg of what I did for the port forwarding, where the "To IP addr" is my computer on our local network where Calibre is loaded. Don't know if it's right, but could you comment?