On the other hand, there are firewall administrators who do extensive filtering on ports 80 and 443 and allow other outgoing traffic by default. We get pretty ticked off when some thermostat, credit card machine, or postage meter decides to send its bizarre and undocumented data stream over port 80 or 443 in the name of firewall compatibility and therefore becomes incompatible with our firewall. (Yes, we can put in exceptions for those machines' IP addresses, but if they didn't try to use HTTP ports, they would Just Work.)