Battle Net?

Battle.net is an online gaming service provided by Blizzard Entertainment. It was launched in January of 1997 with the release of Blizzard's action-RPG — Diablo. Battle.net was the first online gaming service incorporated directly into the games that make use of it, in contrast to the external interfaces used by the other online services at the time. This feature, along with ease of account creations and the absence of member fees, caused Battle.net to become popular among gamers and became a major selling point for Diablo and subsequent Blizzard games.