although otoh in theory there are 65535 usable ports, but shitty shitty firewalls and shitty shitty "sysadmins" often mean you just get 2, and TCP only at that,

although otoh in theory there are 65535 usable ports, but shitty shitty firewalls and shitty shitty "sysadmins" often mean you just get 2, and TCP only at that, but it seems that just that bare minimum "connectivity" works well enough that "regular users" don't notice.