Everyone’s favorite WiFi chip now has Arduino IDE support. This means that you can connect an ESP8266 via a serial port and choose it as a board type in the Arduino IDE now. Make a sketch, click upload and you are in business with a less then $5 IoT device. Pretty nifty!
What’s supported by the build? The short answer is quite a lot — basic functions like pinMode, digitalRead and digitalWrite work as you’d expect. As do interrupts, and the millis and micros functions, and sensible things done to delay to take account of the background activity of WiFi and TCP tasks, and there is a Ticker library for calling functions with a certain cadence.