Nothing stops you from passing a VPN through a TCP connection on port 80 and 443. There are few protocols people haven't tunnelled IP over (DNS included...)
I often have to work behind "smoothwall". AFAIK, it only allows HTTP over port 80 and HTTPS on port 443 - any other protocol on any other port gets blocked, including other protocols over port 80/443.
To bypass this, I wrote a simple ruby script to tunnel TCP connections, while adding fake HTTP headers to get through the firewall.
To bypass this, I wrote a simple ruby script to tunnel TCP connections, while adding fake HTTP headers to get through the firewall.