L4D2

From Protocolinfo

Left 4 Dead 2 (L4D2) is a cooperative first-person shooter game for the PC and Xbox 360. Developed by Valve and distributed by Steam and Electronic Arts.

[edit] Identification

Left 4 Dead 2 seems to use the common Internet ports used by the Steam game client. Author Comment: When hosting a game for other players to join publicly not sure if network communication is server-2-client, peer-2-peer, or a network gateway is used (like battle.net). Listed below are known ports when joining other public servers.