Wi-fi Protocol Structure
Generation IV and V Pokemon games communicate with Nintendo's Wi-Fi servers for various parts of the games.
Nintendo Servers
Nintendo's Wi-Fi servers run Microsoft's IIS and use ASP.NET as the primary scripting language. This data can be confirmed based on the headers sent to the Nintendo DS as well as through error messages sent via browser. The main hostnames of each of these servers are subdomains of nintendowifi.net.
conntest.nintendowifi.net
The connection test servers are the simplest servers. They contain a single webpage which is retrieved to check that Wi-Fi is working properly. The page can be reached with normal HTTP URL retrieval. This address refers to two servers (192.195.204.216; 69.25.139.140) whose DNS records swap every 30 seconds to keep the load balanced.