If another user signs onto a Windows system without the previous user signing out, then the previous user goes into a state known as Disconnected. Programs in the previous user’s session continue to run, but what if you want your program to check whether the session has been disconnected?<\/p>\n
You can subscribe to session state changes by using the If you would rather poll, you can call Or you can go a completely different route and ask whether the current desktop is the target of user input.<\/p>\n Note that the handle returned by Note that this is not the same as disconnectedness. For example, if the user has hit Ctrl<\/kbd>+Alt<\/kbd>+Del<\/kbd>, then there is an input desktop switch to the secure desktop, but the session is not disconnected.<\/p>\n If you are a batch file or a PowerShell script, then your options are more limited. There’s a little program with the presumptuous name WTS\u00adRegister\u00adSession\u00adNotification<\/code> function, passing a window handle to receive the WM_<\/code>WTS\u00adSESSION_<\/code>CHANGE<\/code> message. The wParam<\/code> of the message describes the what happened, and you can use that value to decide to, say, pause various operations while the session is disconnected.<\/p>\nWTS\u00adQuery\u00adSession\u00adInformation<\/code> and ask for the WTS\u00adConnect\u00adState<\/code>.<\/p>\nbool IsOnInputDesktop()\r\n{\r\n auto desktop = GetThreadDesktop(GetCurrentThreadId());\r\n if (!desktop) return false;\r\n\r\n BOOL input = FALSE;\r\n if (!GetUserObjectInformation(desktop, UOI_IO,\r\n &input, sizeof(input), nullptr)) return false;\r\n\r\n return !!input;\r\n}\r\n<\/pre>\nGet\u00adThread\u00adDesktop<\/code> does not need to be (and shouldn’t be) closed.<\/p>\nquery<\/code> that displays information about Terminal Services. In particular you can say query session<\/code> to get a list of sessions, who is signed into each session, and whether the session is connected.<\/p>\n