On the hardware front, you will of course, need the Arduino Ethernet shield and an Arduino board such as the Arduino Uno.

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 from sensors, you could 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 as 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.

To log the data, you will need to have a MicroSD card that you can plug into the Ethernet shield. I don't have a specific brand to recommend, but I used a SanDisk MicroSD card with a normal SD adapter (which worked well for me), so you can also plug it into your computer to check whether the data was correctly logged. Also, make sure that the SD card is formatted using the FAT32...