Avvio di un servizio
Per avviare un servizio, un programma di controllo del servizio apre un handle a un database installato e quindi specifica l'handle in una chiamata alla funzione StartService . Dopo aver avviato il servizio, il programma usa i membri della struttura SERVICE_STATUS_PROCESS restituita dalla funzione QueryServiceStatusEx per tenere traccia dello stato di avanzamento del servizio.
La funzione DoStartSvc nell'esempio seguente illustra come avviare un servizio. La variabile szSvcName è una variabile globale che contiene il nome del servizio da avviare. Per l'esempio completo che imposta questa variabile, vedere SvcControl.cpp.
//
// Purpose:
// Starts the service if possible.
//
// Parameters:
// None
//
// Return value:
// None
//
VOID __stdcall DoStartSvc()
{
SERVICE_STATUS_PROCESS ssStatus;
DWORD dwOldCheckPoint;
DWORD dwStartTickCount;
DWORD dwWaitTime;
DWORD dwBytesNeeded;
// Get a handle to the SCM database.
schSCManager = OpenSCManager(
NULL, // local computer
NULL, // servicesActive database
SC_MANAGER_ALL_ACCESS); // full access rights
if (NULL == schSCManager)
{
printf("OpenSCManager failed (%d)\n", GetLastError());
return;
}
// Get a handle to the service.
schService = OpenService(
schSCManager, // SCM database
szSvcName, // name of service
SERVICE_ALL_ACCESS); // full access
if (schService == NULL)
{
printf("OpenService failed (%d)\n", GetLastError());
CloseServiceHandle(schSCManager);
return;
}
// Check the status in case the service is not stopped.
if (!QueryServiceStatusEx(
schService, // handle to service
SC_STATUS_PROCESS_INFO, // information level
(LPBYTE) &ssStatus, // address of structure
sizeof(SERVICE_STATUS_PROCESS), // size of structure
&dwBytesNeeded ) ) // size needed if buffer is too small
{
printf("QueryServiceStatusEx failed (%d)\n", GetLastError());
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
// Check if the service is already running. It would be possible
// to stop the service here, but for simplicity this example just returns.
if(ssStatus.dwCurrentState != SERVICE_STOPPED && ssStatus.dwCurrentState != SERVICE_STOP_PENDING)
{
printf("Cannot start the service because it is already running\n");
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
// Save the tick count and initial checkpoint.
dwStartTickCount = GetTickCount();
dwOldCheckPoint = ssStatus.dwCheckPoint;
// Wait for the service to stop before attempting to start it.
while (ssStatus.dwCurrentState == SERVICE_STOP_PENDING)
{
// Do not wait longer than the wait hint. A good interval is
// one-tenth of the wait hint but not less than 1 second
// and not more than 10 seconds.
dwWaitTime = ssStatus.dwWaitHint / 10;
if( dwWaitTime < 1000 )
dwWaitTime = 1000;
else if ( dwWaitTime > 10000 )
dwWaitTime = 10000;
Sleep( dwWaitTime );
// Check the status until the service is no longer stop pending.
if (!QueryServiceStatusEx(
schService, // handle to service
SC_STATUS_PROCESS_INFO, // information level
(LPBYTE) &ssStatus, // address of structure
sizeof(SERVICE_STATUS_PROCESS), // size of structure
&dwBytesNeeded ) ) // size needed if buffer is too small
{
printf("QueryServiceStatusEx failed (%d)\n", GetLastError());
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
if ( ssStatus.dwCheckPoint > dwOldCheckPoint )
{
// Continue to wait and check.
dwStartTickCount = GetTickCount();
dwOldCheckPoint = ssStatus.dwCheckPoint;
}
else
{
if(GetTickCount()-dwStartTickCount > ssStatus.dwWaitHint)
{
printf("Timeout waiting for service to stop\n");
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
}
}
// Attempt to start the service.
if (!StartService(
schService, // handle to service
0, // number of arguments
NULL) ) // no arguments
{
printf("StartService failed (%d)\n", GetLastError());
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
else printf("Service start pending...\n");
// Check the status until the service is no longer start pending.
if (!QueryServiceStatusEx(
schService, // handle to service
SC_STATUS_PROCESS_INFO, // info level
(LPBYTE) &ssStatus, // address of structure
sizeof(SERVICE_STATUS_PROCESS), // size of structure
&dwBytesNeeded ) ) // if buffer too small
{
printf("QueryServiceStatusEx failed (%d)\n", GetLastError());
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
return;
}
// Save the tick count and initial checkpoint.
dwStartTickCount = GetTickCount();
dwOldCheckPoint = ssStatus.dwCheckPoint;
while (ssStatus.dwCurrentState == SERVICE_START_PENDING)
{
// Do not wait longer than the wait hint. A good interval is
// one-tenth the wait hint, but no less than 1 second and no
// more than 10 seconds.
dwWaitTime = ssStatus.dwWaitHint / 10;
if( dwWaitTime < 1000 )
dwWaitTime = 1000;
else if ( dwWaitTime > 10000 )
dwWaitTime = 10000;
Sleep( dwWaitTime );
// Check the status again.
if (!QueryServiceStatusEx(
schService, // handle to service
SC_STATUS_PROCESS_INFO, // info level
(LPBYTE) &ssStatus, // address of structure
sizeof(SERVICE_STATUS_PROCESS), // size of structure
&dwBytesNeeded ) ) // if buffer too small
{
printf("QueryServiceStatusEx failed (%d)\n", GetLastError());
break;
}
if ( ssStatus.dwCheckPoint > dwOldCheckPoint )
{
// Continue to wait and check.
dwStartTickCount = GetTickCount();
dwOldCheckPoint = ssStatus.dwCheckPoint;
}
else
{
if(GetTickCount()-dwStartTickCount > ssStatus.dwWaitHint)
{
// No progress made within the wait hint.
break;
}
}
}
// Determine whether the service is running.
if (ssStatus.dwCurrentState == SERVICE_RUNNING)
{
printf("Service started successfully.\n");
}
else
{
printf("Service not started. \n");
printf(" Current State: %d\n", ssStatus.dwCurrentState);
printf(" Exit Code: %d\n", ssStatus.dwWin32ExitCode);
printf(" Check Point: %d\n", ssStatus.dwCheckPoint);
printf(" Wait Hint: %d\n", ssStatus.dwWaitHint);
}
CloseServiceHandle(schService);
CloseServiceHandle(schSCManager);
}
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