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This articles aims to guide you on how to fix "Waiting for Host" bug
Step 1: Go to C:\Program Files (x86)\Common Files\BattlEye (Replace C if you have ARMA installed on a different hard drive but BattlEye usually installs itself on your Windows partition)
Step 2: Delete BEService.exe & BeService_arma2oa.exe
Step 3: Normally launch DayZ Mod or Arma 2 Operation Arrowhead using Steam.
Step 4: A command prompt should open and wait for it to close then the game should launch automatically.
Step 5: Connect to your server and have fun!