ComLink is as the name indicate a component that contain a communication link (IPC, Serial, Ethernet) and contain two Methods : Open and Close. In this case both are optional because the component also have an auto “AlwaysConnected” mode. The output is either OnOpen, OnClose or OnError. OnOpen is shown red because it is Mandatory and not connected. OnClose is shown Green, Open because it is Optional and not connected. OnError is shown Green because it is connected.
Some components will have a fixed list of input/output signals as in this case. The positon of the communication points are computed automatically and the object is sized if needed.