8.1 Ports and connections

Every port has a type (HDMI, SDI, Ethernet, HDBaseT, fibre, DMX, power, …) and a direction: in, out, or bidi. One predicate governs every connection, whether made in the panel or by dragging in the diagram — it rejects joining a port to itself, a type mismatch, a direction clash, and a port that is already occupied.