In this chapter, you've looked at how to create a simple actuator app for the Raspberry Pi using C#. You've learned how to divide an actuator into a set of control parameters. You've also learned the basics of how relays work and how you can control them using the Arduino board. You've persisted control states and logged important security-related control events. As an alternative to using Arduino, you've also learned how to work directly with General Purpose input/output on the Raspberry Pi. In the next chapter, you'll learn how to use the MQTT protocol to publish sensor data and control the actuator over the internet.