A component I/O. Id (like any other Id) is a string generated with 32 random hex charactes, so it is (practically) globally unique. These Ids are used to uniquely refer to ports and components. They are generated via uuid(). PortNumber is used to identify which port is which on a component, contiguous from 0 separately for inputs and outputs. See comments above type definition for details HostId is the unique Id of the component where the port is. For example, all three ports on the same And component will have the same HostId.