DevX.com has published a great article by Mark Watson entitled "Ruby Programming Language Enables Concise Network Programming". Mark gives quick rationales and examples for:

• a simple (not an exaggeration) Web server from scratch in 12 lines of code
• a basic WEBrick server
• a simple REST server with pure sockety madness
• a quick and simple XML-RPC Web service
• a slightly more complex SOAP Web server

A great introduction to some of the networking power at your fingertips with Ruby.