Is there a hypernym of 'inlet' and 'outlet' whose scope is limited to those two words?

A deleted post refers to port. I am familiar with this term in fluid engineering and there is some justification for it in:

ISO/TC131 developed a standard for port identification. ISO 11727 was developed to meet a global need. This standard identifies and provides definitions for proper numerical marking of ports on pneumatic directional control valves. These ports are supply and exhaust flow connections, actuator control connections, and pilot supply connections.

Fluid Power Journal

As used here it implies bi-directionality as you specify but it does not apply exclusively to the fluid connections, so to fit your specification would have to be constrained as the hypernymic noun phrase flow ports.