EQuestionAnswers.com Computer/Electronics Questions and Answers
C, C++, VC++, COM/DCOM, DLL and more
#Login #Sign up  Facebook Twitter TGoogle+
 

#Previous question #Index of COM/DCOM Questions #Next question

DCOM and EXE

DCOM servers are often compiled as EXE executables. DCOM DLL can not execute by itself so there will be a surrogate process which executes the process and DLL will be loaded into the process. DCOM EXE server starts its execution along with a marcellng process. client's call and parameters are exchangd with the help of the marcellng process and LPC or RPC mechanim is used during the buffer/parameter change.

DCOM and SCM service

DCOM exe register its registry entries at the process of COM registration. DCOM server additionally register a service process in the service control manager (SCM). This service process will be started as soon as a Client executes CoCreateInstance/CoGetClassObject OLE API. This will be done through COM/DCOM/OLE framework and Windows registry entries provides the mapping of CLSID/progid to COM EXE server path.

SCM service APIs

SC_HANDLE WINAPI OpenSCManager(
  _In_opt_ LPCTSTR lpMachineName,
  _In_opt_ LPCTSTR lpDatabaseName,
  _In_     DWORD   dwDesiredAccess
);
SC_HANDLE WINAPI CreateService(
  _In_      SC_HANDLE hSCManager,
  _In_      LPCTSTR   lpServiceName,
  _In_opt_  LPCTSTR   lpDisplayName,
  _In_      DWORD     dwDesiredAccess,
  _In_      DWORD     dwServiceType,
  _In_      DWORD     dwStartType,
  _In_      DWORD     dwErrorControl,
  _In_opt_  LPCTSTR   lpBinaryPathName,
  _In_opt_  LPCTSTR   lpLoadOrderGroup,
  _Out_opt_ LPDWORD   lpdwTagId,
  _In_opt_  LPCTSTR   lpDependencies,
  _In_opt_  LPCTSTR   lpServiceStartName,
  _In_opt_  LPCTSTR   lpPassword
);
SC_HANDLE WINAPI OpenService(
  _In_ SC_HANDLE hSCManager,
  _In_ LPCTSTR   lpServiceName,
  _In_ DWORD     dwDesiredAccess
);
BOOL WINAPI ControlService(
  _In_  SC_HANDLE        hService,
  _In_  DWORD            dwControl,
  _Out_ LPSERVICE_STATUS lpServiceStatus
);
BOOL WINAPI DeleteService(
  _In_ SC_HANDLE hService
);
BOOL WINAPI CloseServiceHandle(
  _In_ SC_HANDLE hSCObject
);

DCOM service install

inline BOOL CServiceModule::Install()
{
    if (IsInstalled())
        return TRUE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);
    if (hSCM == NULL)
    {
        MessageBox(NULL, _T("Couldn't open service manager"), m_szServiceName, MB_OK);
        return FALSE;
    }

    // Get the executable file path
    TCHAR szFilePath[_MAX_PATH];
    ::GetModuleFileName(NULL, szFilePath, _MAX_PATH);

    SC_HANDLE hService = ::CreateService(
        hSCM, m_szServiceName, m_szDisplayName,
        SERVICE_ALL_ACCESS, SERVICE_WIN32_OWN_PROCESS,
        SERVICE_DEMAND_START, SERVICE_ERROR_NORMAL,
        szFilePath, NULL, NULL, _T("RPCSS\0"), NULL, NULL);

    if (hService == NULL)
    {
        ::CloseServiceHandle(hSCM);
        MessageBox(NULL, _T("Couldn't create service"), m_szServiceName, MB_OK);
        return FALSE;
    }

    ::CloseServiceHandle(hService);
    ::CloseServiceHandle(hSCM);
    return TRUE;
}
BOOL CServiceModule::IsInstalled()
{
    BOOL bResult = FALSE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

    if (hSCM != NULL)
    {
        SC_HANDLE hService = ::OpenService(hSCM, m_szServiceName, SERVICE_QUERY_CONFIG);
        if (hService != NULL)
        {
            bResult = TRUE;
            ::CloseServiceHandle(hService);
        }
        ::CloseServiceHandle(hSCM);
    }
    return bResult;
}

DCOM service uninstall

inline BOOL CServiceModule::Uninstall()
{
    if (!IsInstalled())
        return TRUE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

    if (hSCM == NULL)
    {
        MessageBox(NULL, _T("Couldn't open service manager"), m_szServiceName, MB_OK);
        return FALSE;
    }

    SC_HANDLE hService = ::OpenService(hSCM, m_szServiceName, SERVICE_STOP | DELETE);

    if (hService == NULL)
    {
        ::CloseServiceHandle(hSCM);
        MessageBox(NULL, _T("Couldn't open service"), m_szServiceName, MB_OK);
        return FALSE;
    }
    SERVICE_STATUS status;
    ::ControlService(hService, SERVICE_CONTROL_STOP, &status);

    BOOL bDelete = ::DeleteService(hService);
    ::CloseServiceHandle(hService);
    ::CloseServiceHandle(hSCM);

    if (bDelete)
        return TRUE;

    MessageBox(NULL, _T("Service could not be deleted"), m_szServiceName, MB_OK);
    return FALSE;
}

You have viewed 1 page out of 66. Your COM/DCOM learning is 0.00% complete. Login to check your learning progress.

 Vote 0

Similar topics related to this section

# COM DCOM Interview Questions and Answers :: ALL Interview .com
# COM DCOM - COM DCOM Interview Questions
# COM interview questions | TechInterviews
# COM Interview Questions - CodeProject
# Com Dcom Interview Questions - Com and Dcom in Asp Net
# ATL Interview Questions and Answers :: ALL Interview .com
# ActiveX Interview Questions and Answers :: ALL Interview .com

* #1 webmaster Sat 03 May/2014 07:39:23(GMT)  Like 0 Unlike 0

Dear Users,

We are pleased to inform you that a forum/blog has been incorporated with www.mybestnotes.co.in. You are welcomed to add your comments, requests, codes, solutions and feedback to it. Please login(if already a member) or signup(for free) to avail to this facility.

Regards,
Webmaster

Your message goes here:

Name:Guest
Email:anonymous@unknown.com
My Post:*
Secutiry Code: ******  *
Preview this compose before posting this in discussion forum.
 
Note:
  1. Use [Sxx] code to show smiles. Example [S02]
  2. Use [URL ], example [URL http://www.google.com/]
  3. To display code or un formatted text use [CODE] [/CODE]. Example: [CODE] printf("Hello world"); [/CODE]
 [S01]   [S02]   [S03]   [S04]   [S05]   [S06]   [S07]   [S08] 
 [S09]   [S10]   [S11]   [S12]   [S13]   [S14]   [S15]   [S16] 
 [S17]   [S18]   [S19]   [S20]   [S21]   [S22]   [S23]   [S24] 

Note: Only members are allowed, * fields are mandatory.