Blocking based purely on port numbers is so ridiculously easy to circumvent that it seems pointless. Are you sure you aren't just falling foul of a default firewall? Residential accounts here in the UK aren't well suited for commercial use because they're asymmetric and provide very low upstream bandwidth, and because they do not have availability guarantees. I'm struggling to imagine how they could have worded a condition to prevent hosting a public-facing web server without also ruling out internet cameras, skype, peer-to-peer file sharing and online games and so on. None of the ISPs I've used here in the UK have imposed restrictions on what services can be used, except that they're not allowed to be used for anything that damages the service. I forget the exact wording but I seem to remember reading some terms that ruled out using the service for illegal activity, but of course the fact that it's illegal trumps anything the Ts&Cs might say. The closest any of them have come to actually blocking services that I can think of has been throttling peer-to-peer file sharing traffic, and throttling people who have exceeded their data quota. I fully accept that it's different there, but don't assume that ISPs everywhere are like yours.