On Thu, 4 Oct 2012 10:44:57 +0100, cl@isbd.net said:
I don't want it to provide any sort of access from outside, I just want to be able to reverse tunnel down the connection to access port 80 on the system on the boat.
In my opinion, you are making life unnecessarily complicated for yourself. The easy way to do this is to set up a VPN (OpenVPN is reasonably straightforward) from the boat to wherever you want, using multiple VPN connections if necessary. Then you can firewall incoming connections over the VPN to allow access from only those places you specify.
That would be a lot more secure, and, once set up, somewhat easier to manage.