(Really? -2? I am actually surprised that this is a problem. I have to share web apps with my friends, in both directions, regularly. It's never been a problem. Everyone has a publicly-routeable address these days.)
Sadly, not all ISPs allow this. I run into this frustration whenever I visit my parents. They use a wireless ISP which does not provide each customer with a public facing IP. They all share the same public IP address and therefore can not receive incoming connections.
If I want to share my node app with someone, I just tell them to visit http://snowball2.jrock.us:4545/ and there we are.
(Really? -2? I am actually surprised that this is a problem. I have to share web apps with my friends, in both directions, regularly. It's never been a problem. Everyone has a publicly-routeable address these days.)