Project Description


This project describes about using the Ethernet Shield W5100 as a Web server.


  • Implements IPV4. This example uses TCP/IP.
  • The default gateway is disabled by default. This means the device will only respond to requests from your local/private network.
  • If for some reason you want it to respond to Internet requests, you can map a port through your router and set the default gateway to The device will then respond through the router. For more info, do a search for “port address translation.”
  • Client requests and response codes are written to the console with 115200 baud.
  • This web server is appropriate for text only, so any images must be hosted on a REAL web server (or use a more powerful Arduino).
  • Keep realistic expectations. If your project exceeds basic automation requirements, consider a full embedded system or server operating system.



Arduino Uno

Ethernet Shield W5100


After installing Arduino software, simply connect the USB and load this sketch to your Arduino device. The device and Ethernet shield can be powered by USB.

The requests are handled in the void respond() function.

The test page shows you how to pass in args and write them back in the response:

Each request must be handled in full before the Arduino can respond to the next request, so make them short.

Example output:



Author:Mark Scammacca

Tags:201802,Arduino Uno,Ethernet shield W5100