Server Name : Calibre1
Schedule : Always
Server IP Address : 192.168.1.6
External Port Start: 31811
External Port End: 31811
Protocol TCP and UDP if possible. Otherwise just TCP
Internal Port Start: 8090
Internal Port End: 8090
Remote Ip: Leave blank
Once setup, you should be able to access the content server from the internal network using:
http://192.168.1.6:8090
You should be able to access from the internet using:
http://mylibrary.duckdns.org:31811
Finally, if you can now access it from the internet, change the 31811 external port to some other number. Select one at random beween, say, 20000 and 59000, and modify your port forwarding settings accordingly, and remember to substitute the new port number when accessing from the internet. If you stay with the port number I used here, everyone who reads this post will know both the internet address and port number to access your content server. This is why it is important to setup username and password security on your content server.