From the FAQ:
Have you tried using one of those ports?Q: I am behind a firewall and can't submit or retrieve blocks, what should I do?
A: If you are behind a firewall, change the servername to be sbp.pns.net and use port 80 or port 22. If this still does not work for you, please contact us with a port you know you can access and we will set up the proxy server to listen on that port