The GameSpy has discontinued its services and due to this reason Bohemia Interactive (BI) have offered an alternative for the BI Community. BI has released the update 1.63 for ArmA 2: Operation Arrowhead (see changelog). Besides the fixes and optimizations, the update focuses on the transition of the multiplayer online support from GameSpy to Steam services. Because the Steam based matchmaking requires Steam client software, this update is only available via Steam website. If you have purchased a retail copy of the ArmA 2 series, you can activate all the CD-keys, including DLCs and Operation Arrowhead expansion, on Steam website. (see walkthrough).
For the other game titles affected by the GameSpy service shutdown, but not updated to work with Steam services, and also for those players who wish to stay with the retail version of the game titles, BI have implemented the Server Browser for hosting and connecting to servers without the GameSpy services. Here server owners may add their servers and players may use the IP addresses to connect to them. Also BI have added articles for each game to Support website and as always the technical support staff is ready to help via e-mail email@example.com.