Schedule machine to wake up

Question

What's the best way to programmatically cause a Windows XP (or above) machine to wake up at a specific time. (Ideally a lot like how Media Center can start up automatically to record a particular TV program)

I've got a Windows service (written in C#) and I'd like this service to be able to cause the machine it is hosted on to start up at predetermined times.

Are there any BIOS settings or prerequisites (eg. ACPI) that need to be configured for this to work correctly?

This machine would be using dialup or 3G wireless modem, so unfortunately it can't rely on Wake on LAN.

Answer 1

You can use waitable timers to wake from a suspend or hibernate state. From what I can find, it is not possible to programmatically wake from normal shut down mode (soft off/S5), in that case, you need to specify a WakeOnRTC alarm in BIOS. To use waitable timers from C#, you need pInvoke. The import declarations are:

public delegate void TimerCompleteDelegate();

[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr CreateWaitableTimer(IntPtr lpTimerAttributes, bool bManualReset, string lpTimerName);

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool SetWaitableTimer(IntPtr hTimer, [In] ref long pDueTime, int lPeriod, TimerCompleteDelegate pfnCompletionRoutine, IntPtr pArgToCompletionRoutine, bool fResume);

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool CancelWaitableTimer(IntPtr hTimer);

You can use those functions in the following way:

public static IntPtr SetWakeAt(DateTime dt)
{
    TimerCompleteDelegate timerComplete = null;

    // read the manual for SetWaitableTimer to understand how this number is interpreted.
    long interval = dt.ToFileTimeUtc(); 
    IntPtr handle = CreateWaitableTimer(IntPtr.Zero, true, "WaitableTimer");
    SetWaitableTimer(handle, ref interval, 0, timerComplete, IntPtr.Zero, true);
    return handle;
}

You can then cancel the waitable timer with CancelWaitableTimer, using the returned handle as an argument.

Your program can hibernate and sleep using pInvoke:

[DllImport("powrprof.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool SetSuspendState(bool hibernate, bool forceCritical, bool disableWakeEvent);

public static bool Hibernate()
{
    return SetSuspendState(true, false, false);
}

public static bool Sleep()
{
    return SetSuspendState(false, false, false);
}

Your system may not allow programs to let the computer enter hibernation. You can call the following method to allow hibernation:

public static bool EnableHibernate()
{
    Process p = new Process();
    p.StartInfo.FileName = "powercfg.exe";
    p.StartInfo.CreateNoWindow = true;
    p.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
    p.StartInfo.Arguments = "/hibernate on"; // this might be different in other locales
    return p.Start();
}