Ti lascio qui un estratto di una pagina web che ho cercato. Spiega che la connessione tra players avviene con tecnica p2p

Speaking about the upcoming Modern Warfare 2 in a podcast, Infinity Ward Community Manager Rob "fourzerotwo" Bowling dropped a bombshell that has the die-hard PC gamers reeling: Not only will Modern Warfare 2 not support user-created mods, but the game will not support dedicated servers for multiplayer - instead, the PC version will use the same peer-to-peer matchmaking formula of its console brethren.
"The team's focusing on having it very equal on every platform," said Bowling, and it's true that lack of a traditional PC server browser - where players are able to sort dedicated third-party servers by gametype/map/players/ping/etc. and choose which one they want to join - has hardly crippled the popular console versions of the first Modern Warfare. In theory, the "console" archetype simply distributes the hosting load to the player with the best connection - and should they drop, it smoothly finds another host who can continue the match.

Come faccio ad implementare una tecnica simile aggirando il problema del serve(poichè i server costano cmq soldini)