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Wake the PC from standby or hibernation

, 3 Feb 2014 CPOL 71.7K 2.4K 110
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How to automatically wake up the PC at some time in the future.

Introduction

Sometimes, it might be useful to automatically turn on the PC at some time in the future. To do this, we'll use a little trick: usually, a computer is not capable of powering itself up, but it's able to recover from standby or hibernation (if the hardware is capable of it).

Background

The code is mainly a wrapper around two system timer functions: CreateWaitableTimer and SetWaitableTimer. That's because the timer is able to resume the system, if told to. The declaration is:

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

[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool SetWaitableTimer(SafeWaitHandle hTimer, 
                                            [In] ref long pDueTime, 
                                                      int lPeriod,
                                                   IntPtr pfnCompletionRoutine, 
                                                   IntPtr lpArgToCompletionRoutine, 
                                                     bool fResume);

We need to provide a date and a time, but SetWaitableTimer asks for a long integer value... DateTime.ToFileTime() is the function that we'll use to convert date/times from managed to system representations. 

Take a look at the core of the program, where we call the two API functions: 

long waketime = (long)e.Argument;

using (SafeWaitHandle handle = 
         CreateWaitableTimer(IntPtr.Zero, true, 
         this.GetType().Assembly.GetName().Name.ToString() + "Timer"))
{
    if (SetWaitableTimer(handle, ref waketime, 0, 
                         IntPtr.Zero, IntPtr.Zero, true))
    {
        using (EventWaitHandle wh = new EventWaitHandle(false, 
                                             EventResetMode.AutoReset))
        {
            wh.SafeWaitHandle = handle;
            wh.WaitOne();
        }
    }
    else
    {
        throw new Win32Exception(Marshal.GetLastWin32Error());
    }
}

You can notice an "e.Argument" in the first line. It's there because the following block of code pauses the execution of the thread until the timer reaches the "wake time" value:

using (EventWaitHandle wh = new EventWaitHandle(false, 
                                EventResetMode.AutoReset))
{
    wh.SafeWaitHandle = handle;
    wh.WaitOne();
}

So, to avoid blocking the UI thread, we need to put that block of code into a separate thread, controlled by a BackgroundWorker object to which we'll pass the wake time as an argument. This is where "e.Argument" comes from.

I needed to create a class for easy re-use, so I decided to provide an event: "Woken". The event gets triggered as soon as the background thread exits:

public event EventHandler Woken;

void bgWorker_RunWorkerCompleted(object sender, 
              RunWorkerCompletedEventArgs e)
{
    if (Woken != null)
    {
        Woken(this, new EventArgs());
    }
}

So, to recap, this is the full class: 

using System;
using System.Text;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
using System.ComponentModel;
using System.Threading;

namespace WakeUPTimer
{
    class WakeUP
    {
        [DllImport("kernel32.dll")]
        public static extern SafeWaitHandle CreateWaitableTimer(IntPtr lpTimerAttributes, 
                                                                  bool bManualReset,
                                                                string lpTimerName);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SetWaitableTimer(SafeWaitHandle hTimer, 
                                                    [In] ref long pDueTime, 
                                                              int lPeriod,
                                                           IntPtr pfnCompletionRoutine, 
                                                           IntPtr lpArgToCompletionRoutine, 
                                                             bool fResume);

        public event EventHandler Woken;

        private BackgroundWorker bgWorker = new BackgroundWorker();

        public WakeUP()
        {
            bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
            bgWorker.RunWorkerCompleted += 
              new RunWorkerCompletedEventHandler(bgWorker_RunWorkerCompleted);
        }

        public void SetWakeUpTime(DateTime time)
        {
            bgWorker.RunWorkerAsync(time.ToFileTime());
        }

        void bgWorker_RunWorkerCompleted(object sender, 
                      RunWorkerCompletedEventArgs e)
        {
            if (Woken != null)
            {
                Woken(this, new EventArgs());
            }
        }

        private void bgWorker_DoWork(object sender, DoWorkEventArgs e) 
        {
            long waketime = (long)e.Argument;

            using (SafeWaitHandle handle = 
                      CreateWaitableTimer(IntPtr.Zero, true, 
                      this.GetType().Assembly.GetName().Name.ToString() + "Timer"))
            {
                if (SetWaitableTimer(handle, ref waketime, 0, 
                                       IntPtr.Zero, IntPtr.Zero, true))
                {
                    using (EventWaitHandle wh = new EventWaitHandle(false, 
                                                           EventResetMode.AutoReset))
                    {
                        wh.SafeWaitHandle = handle;
                        wh.WaitOne();
                    }
                }
                else
                {
                    throw new Win32Exception(Marshal.GetLastWin32Error());
                }
            }
        }

    }
}

Using the Code

If we have a Button and a DateTimePicker on a form, we can write something like this:

private void button1_Click(object sender, EventArgs e)
{
    WakeUP wup = new WakeUP();
    wup.Woken += WakeUP_Woken;
    wup.SetWakeUpTime(dateTimePicker1.Value);
}

private void WakeUP_Woken(object sender, EventArgs e)
{
    // Do something 
}

And to suspend the system:

Application.SetSuspendState(PowerState.Suspend, false, false);

Important note: the last parameter, disableWakeEvent, needs to be false.

Troubleshooting

If the software doesn't work, it doesn't necessarily mean that your hardware doesn't support it. It's possible that some Windows setting is preventing the awakening of the system. To make sure that the settings are correct, check that: 

  • In "Control Panel > Power Options > Change Plan Settings > Change Advanced Power Settings > Sleep > Allow Wake Timers", all items are enabled.
  • If there is no password set on your Windows account, make sure that in "Control Panel > Power Options > Change Plan Settings > Change Advanced Power Settings > Brad / Additional Settings > Require a password on wakeup", all items are disabled (thanks nanfang).

Points of Interest

I used a BackgroundWorker for a simple reason: the code in the Woken event must be in the same thread of the user interface for easy access to controls. With standard thread management, that's not so trivial.

History

  • v1.0 - 2009/12/31 - Initial release.
  • v1.1 - 2010/10/03 - Fixed a bug and updated article (troubleshooting section).

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

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Comments and Discussions

 
QuestionFor Windows 8 finally move the mouse to turn the screen on again. Pin
andrew douse20-Apr-15 21:39
memberandrew douse20-Apr-15 21:39 
QuestionCan you provide me with executable please? Pin
Member 20108973-Mar-15 20:10
memberMember 20108973-Mar-15 20:10 
QuestionFine!!!!!!! Pin
Volynsky Alex3-Feb-14 11:07
professionalVolynsky Alex3-Feb-14 11:07 
GeneralMy vote of 5 Pin
peteSJ3-Feb-14 8:50
memberpeteSJ3-Feb-14 8:50 
QuestionNice, dude! My vote of 5! Pin
Viktor Signaievskyi1-Feb-14 10:39
memberViktor Signaievskyi1-Feb-14 10:39 
BugSystem doesn't wake up Pin
suneth_ac31-Aug-13 22:23
membersuneth_ac31-Aug-13 22:23 
QuestionCode works, but monitor does not come on Pin
PuWii21-May-13 21:12
groupPuWii21-May-13 21:12 
AnswerUpdate: Code works, but monitor does not come on Pin
PuWii26-May-13 20:12
groupPuWii26-May-13 20:12 
GeneralMy vote of 5 Pin
Deveshdevil8-Apr-13 0:39
memberDeveshdevil8-Apr-13 0:39 
Questionit does't work well like this. Pin
lsf_20085-Nov-12 20:15
memberlsf_20085-Nov-12 20:15 
QuestionCould you code it using vc++? thanks! Pin
lsf_20084-Nov-12 15:41
memberlsf_20084-Nov-12 15:41 
Questionhow to make it wakeup daily instead of specified date? Pin
lordrt19-Aug-12 22:01
memberlordrt19-Aug-12 22:01 
QuestionFuture dates won't work Pin
ChrisPKnight21-Jun-12 6:14
memberChrisPKnight21-Jun-12 6:14 
AnswerRe: Future dates won't work Pin
Daniele Di Sarli21-Jun-12 11:19
memberDaniele Di Sarli21-Jun-12 11:19 
QuestionMy vote of 5 - Now I don't have to turn the server on in the morning Pin
enhzflep16-Jun-12 20:49
memberenhzflep16-Jun-12 20:49 
QuestionDon't wake up [modified] Pin
chenwangfen13-Nov-11 15:55
memberchenwangfen13-Nov-11 15:55 
AnswerRe: Don't wake up Pin
Daniele Di Sarli13-Nov-11 19:42
memberDaniele Di Sarli13-Nov-11 19:42 
GeneralRe: Don't wake up [modified] Pin
chenwangfen14-Nov-11 15:43
memberchenwangfen14-Nov-11 15:43 
GeneralRe: Don't wake up Pin
Daniele Di Sarli17-Nov-11 23:34
memberDaniele Di Sarli17-Nov-11 23:34 
GeneralMy vote of 5 Pin
Kanasz Robert10-Nov-11 23:41
memberKanasz Robert10-Nov-11 23:41 
GeneralWorks Great Pin
Prasad_MCA15-Aug-11 7:28
memberPrasad_MCA15-Aug-11 7:28 
GeneralThe BackgroundWorker is busy Pin
hnldp2sh10-Mar-11 15:34
memberhnldp2sh10-Mar-11 15:34 
GeneralRe: The BackgroundWorker is busy Pin
Daniele Di Sarli11-Mar-11 4:50
memberDaniele Di Sarli11-Mar-11 4:50 
GeneralRe: The BackgroundWorker is busy Pin
h3mp17-Oct-13 1:25
memberh3mp17-Oct-13 1:25 
GeneralWorks very well with standby and hibernate [modified] Pin
gauravkale22-Feb-11 4:00
membergauravkale22-Feb-11 4:00 
GeneralRe: Works very well with standby and hibernate Pin
Daniele Di Sarli22-Feb-11 8:19
memberDaniele Di Sarli22-Feb-11 8:19 
GeneralScreen stays black Pin
neojudgment18-Jan-11 5:28
memberneojudgment18-Jan-11 5:28 
GeneralRe: Screen stays black Pin
Daniele Di Sarli18-Jan-11 5:38
memberDaniele Di Sarli18-Jan-11 5:38 
GeneralRe: Screen stays black Pin
Daniele Di Sarli18-Jan-11 5:43
memberDaniele Di Sarli18-Jan-11 5:43 
GeneralRe: Screen stays black Pin
neojudgment18-Jan-11 6:03
memberneojudgment18-Jan-11 6:03 
GeneralRe: Screen stays black Pin
Daniele Di Sarli18-Jan-11 6:56
memberDaniele Di Sarli18-Jan-11 6:56 
GeneralRe: Screen stays black Pin
neojudgment27-Jan-11 10:32
memberneojudgment27-Jan-11 10:32 
GeneralRe: Screen stays black Pin
Daniele Di Sarli27-Jan-11 10:53
memberDaniele Di Sarli27-Jan-11 10:53 
GeneralRe: Screen stays black Pin
Si.Jinmin26-Apr-12 20:34
memberSi.Jinmin26-Apr-12 20:34 
QuestionI want to write an event when the machine wakes up. How to go about it Pin
digvijay_nath11-Oct-10 17:16
memberdigvijay_nath11-Oct-10 17:16 
AnswerRe: I want to write an event when the machine wakes up. How to go about it [modified] Pin
Karthik. A11-Oct-10 18:48
memberKarthik. A11-Oct-10 18:48 
GeneralIt works on Windows Vista Ultimate x64 Pin
hswear33-Oct-10 8:40
memberhswear33-Oct-10 8:40 
GeneralRe: It works on Windows Vista Ultimate x64 Pin
Daniele Di Sarli3-Oct-10 10:06
memberDaniele Di Sarli3-Oct-10 10:06 
AnswerRe: It works on Windows Vista Ultimate x64 Pin
digvijay_nath11-Oct-10 17:19
memberdigvijay_nath11-Oct-10 17:19 
GeneralRe: It works on Windows Vista Ultimate x64 Pin
Daniele Di Sarli12-Oct-10 5:23
memberDaniele Di Sarli12-Oct-10 5:23 
GeneralExcellent!!! Pin
Shanthi Diana22-Aug-10 9:32
memberShanthi Diana22-Aug-10 9:32 
GeneralRe: Excellent!!! Pin
Daniele Di Sarli23-Aug-10 3:38
memberDaniele Di Sarli23-Aug-10 3:38 
GeneralIt doesn't work for me Pin
nanfang25-Jul-10 9:45
membernanfang25-Jul-10 9:45 
GeneralRe: It doesn't work for me Pin
Daniele Di Sarli25-Jul-10 10:07
memberDaniele Di Sarli25-Jul-10 10:07 
GeneralRe: It doesn't work for me Pin
nanfang26-Jul-10 17:47
membernanfang26-Jul-10 17:47 
GeneralRe: It doesn't work for me Pin
Daniele Di Sarli26-Jul-10 23:35
memberDaniele Di Sarli26-Jul-10 23:35 
GeneralRe: It doesn't work for me Pin
Oscar Londono3-Oct-10 3:13
memberOscar Londono3-Oct-10 3:13 
GeneralHi Pin
fanan_boy13-May-10 13:12
memberfanan_boy13-May-10 13:12 
Generalhi Pin
fanan_boy12-May-10 5:20
memberfanan_boy12-May-10 5:20 
GeneralRe: hi Pin
Daniele Di Sarli12-May-10 5:59
memberDaniele Di Sarli12-May-10 5:59 

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