DNS Question: Is there a way to update my changing ip address to a domain name?

Daniel wants to have www.danielsdomainname.com point to his port 81 on his desktop pc. But here is the catch his isp changes his IP every so often and Daniel doesn’t want to have to update the dns records manually.

There is a possibility that his isp blocks port 8 0- he’s not sure. Is there a way to test if its blocked or a dynamic dns service that is free and supports www.domainname.com to point to http://ipaddress:PortOtherThan80?

ANY IDEAS??

Edit: 8:00pm I found this its freedns from afraid dot org. I don’t have any experience with them but I will give it a shot with my home machine over the weekend.