Fanuc FOCAS is a set of library files (dll), that when embedded inside a Visual Studio application, can access almost all of the information inside of the CNC. The Fanuc FOCAS libraries access the CNC using either Ethernet or HSSB.
MachineMetrics uses these libraries to access information directly from the control via ethernet. Many FANUC controls that are 10-15 years old or newer support FOCAS. Controls with an "i" series designation may support FOCAS. Find out if your control supports FOCAS by reading this article.