I found a useful service on http://www.blindhog.net/identify-your-public-ip-address-with-telnet/ and thought I’d like to have a go at making something myself. So, now you can telnet to mcgrane.uk and it’ll tell you what your IP is.
Your IP is 127.0.0.1
This can be useful in conditions where I want to know which ISP a server is using but cannot use a web browser to go to http://www.whatismyip.com. I’ve added a rate limit so repeated connections within 10 seconds of the last will cause the IP to be temporarily banned.