Node port

A port is the small stub on the edge of a node where a wire begins or ends. It is the smallest named part of a node graph and the one that carries the most meaning, because a port is typed: it declares what kind of value passes through it, and a wire that would carry the wrong kind will not land. That refusal is the design content of the whole family. A reader learns the model of the system from what the surface declines to connect, without a page of documentation and without an error appearing after the fact.

The vocabulary is unsettled and worth knowing in all three spellings. Blender calls it a socket and codes it twice over, by colour for the data it carries and by shape for whether the value is a single item or a field, so the compatibility rule is legible before a wire is pulled. React Flow calls it a Handle and makes its position and connectability properties of the component. Others say pin or connection point. The bare word “handle” is the one to avoid in prose, because in most interfaces a drag handle is a grip that says grab me here, which is very nearly the opposite claim: a grip moves the thing it sits on, a port connects it to something else.

Three details separate a good port from a frustrating one. The hit target has to be larger than the drawn stub, usually by a generous margin, because a 6px dot is not something a pointer or a finger can be expected to find; the drawn size is a matter of taste and the target is a matter of arithmetic. Ports should light up while a wire is in flight, so the answer to “where can this go” arrives before the reader guesses wrong rather than after. And a refusal has to say why: a wire that snaps back with no explanation reads as a broken drag, while one that reports a type mismatch teaches the rule it just enforced. Direction is usually implied by side, inputs on the left and outputs on the right, along with the convention that an input accepts one wire and an output fans out to many.

Ports are also where a node graph’s accessibility either exists or does not. A connection is a pair of ports, so a keyboard path through the graph needs each port to be reachable and each connection to be makeable without a pointer, which in practice means a port is a real focusable control with a name that includes its node, its direction and its type. Building that once is far cheaper than retrofitting it, and it has a useful side effect: naming every port properly forces the type model to be explicit, which is what makes the refusal explainable in the first place.