This Python program shows how applications usually handle Internet Protocol sockets. On a personal computer running Windows, Linux, BSD, or Android, your program communicates over the Internet by:
The W5100 has an Ethernet interface and four Internet sockets built in to the chip, and any microcontroller that can host an SPI interface can use them. As an example, I've created an Arduino sketch that hosts a server a server to ROT-13 encode any messages it receives on a LAN using the UDP protocol. Although the demo is written as a sketch, It's intended to be adapted into a C program to run on any of the usual 8- or 16-bit embedded processors. There are two files in the wiztalk demo sketch: wiztalk.pde which contains the logic for communication with the W5100, and wiz5100.h which defines all the symbols used in the communication.
The Python program mentioned at the beginning of this article is intended to work with the wiztalk server. The Python program joins up its command-line arguments into a string, sends the string to the server, and prints the encoded result.
The wiztalk Arduino sketch code is available as a .ZIP file.
I've found the WIZ811MJ board that I used in the demo at Sparkfun, or Saelig across the lake in New York, or Creatron if you're in Toronto and in a hurry.