On the hardware side, you will of course need the Arduino Uno board and Arduino Ethernet shield.

You will also need a sensor to measure some data. As this book is about how to use the Ethernet shield and not how to measure data from sensors, you can actually take any sensor of your choice.

I used a DHT11 sensor, which is a digital temperature and humidity sensor. I chose this sensor for this chapter and for many chapters of the book since it is a very cheap sensor and easy to interface with Arduino. Along with the DHT11 sensor, you will also need a 4.7k Ohm resistor.

You can also use other kind of sensors. You can use analog sensors, which return a signal depending on the measured data. For example, the TMP36 sensor is an analog temperature sensor that returns a voltage proportional to the ambient temperature.

Other kind of sensors you can use here are sensors based on the SPI or I2C protocols, which are digital communication protocols that are easy to use...