Send command to service from C++ - c++

Question

how can I send command to a Windows service from C++? Equivalent .NET code is:
ServiceController sc = new ServiceController("MyService");
sc.ExecuteCommand(255);

Answer 1

From native C++, you will need to:
Open a handle to the service control manager,
Use the service control manager to obtain a service handle for the service you want to control,
Send a control code or codes to the service, and
Close the handles opened in steps 1 and 2.
For example, this code restarts the time synchronization service. First, I create a wrapper class for the service handles, to close them automatically when leaving the block.
class CSC_HANDLE
{
public:
CSC_HANDLE(SC_HANDLE h) : m_h(h) { }
~CSC_HANDLE() { ::CloseServiceHandle(m_h); }
operator SC_HANDLE () { return m_h; }
private:
SC_HANDLE m_h;
};
Then, I open the service control manager (using OpenSCManager()) and the service I want to control. Note that the dwDesiredAccess parameter to OpenService() must include permissions for each control I want to send, or the relevant control functions will fail.
BOOL RestartTimeService()
{
CSC_HANDLE hSCM(::OpenSCManager(NULL, SERVICES_ACTIVE_DATABASE, GENERIC_READ));
if (NULL == hSCM) return FALSE;
CSC_HANDLE hW32Time(::OpenService(hSCM, L"W32Time", SERVICE_START | SERVICE_STOP | SERVICE_QUERY_STATUS));
if (NULL == hW32Time) return FALSE;
To stop the service, I use ControlService() to send the SERVICE_CONTROL_STOP code, and then check the return value to make sure the command succeeded. If any error other than ERROR_SERVICE_NOT_ACTIVE is reported, I assume that starting the service is not going to succeed.
SERVICE_STATUS ss = { 0 };
::SetLastError(0);
BOOL success = ::ControlService(hW32Time, SERVICE_CONTROL_STOP, &ss);
if (!success)
{
DWORD le = ::GetLastError();
switch (le)
{
case ERROR_ACCESS_DENIED:
case ERROR_DEPENDENT_SERVICES_RUNNING:
case ERROR_INVALID_HANDLE:
case ERROR_INVALID_PARAMETER:
case ERROR_INVALID_SERVICE_CONTROL:
case ERROR_SERVICE_CANNOT_ACCEPT_CTRL:
case ERROR_SERVICE_REQUEST_TIMEOUT:
case ERROR_SHUTDOWN_IN_PROGRESS:
return FALSE;
case ERROR_SERVICE_NOT_ACTIVE:
default:
break;
}
}
After instructing the service to stop, I wait for the service manager to report that the service is in fact stopped. This code has two potential bugs, which you may wish to correct for production code:
Sleep(1000) will suspend the message loop on this thread, so you should use another method to delay execution if this function will run on a UI thread. You can construct a suitable sleep-with-message-loop using MsgWaitForMultipleObjectsEx().
The DWORD returned from GetTickCount() will wrap around to zero eventually; if it wraps around while this function is waiting, the wait may give up sooner than I intended.
DWORD waitstart(::GetTickCount());
while (true)
{
ZeroMemory(&ss, sizeof(ss));
::QueryServiceStatus(hW32Time, &ss);
if (SERVICE_STOPPED == ss.dwCurrentState) break;
::Sleep(1000);
DWORD tick(::GetTickCount());
if ((tick < waitstart) || (tick > (waitstart + 30000))) return FALSE;
}
Finally, knowing that the service is in a stopped state, I call StartService() run it again.
success = ::StartService(hW32Time, 0, NULL);
if (!success) return FALSE;
return TRUE;
}

Answer 2

You use ControlService, see Service Control Requests.

Answer 3

Here is a little program which will connect to a service called "MYSERVICE" then send a command 141 (which is defined by the service)
// ServiceCommunicator.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <Windows.h>
#include <iostream>
using namespace std;
int main()
{
SC_HANDLE managerHandle;
SC_HANDLE serviceHandle;
SERVICE_STATUS controlParms;
DWORD retStatus;
managerHandle = OpenSCManager(NULL, NULL, GENERIC_READ);
if (NULL != managerHandle)
{
serviceHandle = OpenService(managerHandle, L"MYSERVICE", SERVICE_USER_DEFINED_CONTROL | SERVICE_QUERY_STATUS);
if (NULL != serviceHandle)
{
cout << "connected to Service" << endl;
retStatus = ControlService(serviceHandle, 141, &controlParms);
if (retStatus)
{
//Get the return code from the service
cout << "For command 141, return code from service was " << controlParms.dwWin32ExitCode << endl;
}
else
cout << "Sending command 141 failed" << endl;
CloseServiceHandle(serviceHandle);
}
else
{
cout << "could not connect to Service" << endl;
}
CloseServiceHandle(managerHandle);
}
else
{
cout << "could not open service manager" << endl;
}
return 0;
}