FILE: HELSVC.EXE Implements an OLE Server in a Service

• Microsoft OLE libraries included with: - Microsoft Windows NT version 4.0

SUMMARY

The HELSVC sample is a simple OLE Automation server implemented in a service called "Hello OLE Server Service."

The following file is available for download from the Microsoft Software Library:

 ~ Helsvc.exe (size: 39742 bytes) 

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from
               Online Services

MORE INFORMATION

This server implements one application object with a dual interface. It also registers the application object in the RunningObjectTable so that any client can access it. The sample includes a Visual Basic client that can control the server. The sample does not use any framework such as MFC, ATL, etc.

Implementation Notes

NT 4.0 removes the limitations of using OLE in services that are described in the following article in the Microsoft Knowledge Base:

   ARTICLE_ID: Q149571
   TITLE     : Using OLE in Services in Windows NT 3.51

   "LocalService"
   "Installing as a Win32 Service or User Account"

When the service starts, it registers a multiple-use class factory. It then registers an object in the Running Object Table using ROTFLAGS_ALLOWANYCLIENT, which allows clients in any security context to bind to the object using IRunningObjectTable::GetObject or GetActiveObject (if the appropriate permissions are specified in the server's access permissions using the DCOMCNFG tool).

If ROTFLAGS_ALLOWANYCLIENT is not used in the ROT registration, only clients in the same security context as the server will be able to bind to it. RegisterActiveObject currently does not support ROTFLAGS_ALLOWANYCLIENT, so the sample provides a new function, MyRegisterActiveObject, which supports this flag.

IRunningObjectTable::Register supports this flag. Registration using this flag requires a registry entry similar to the following to prevent a CO_E_WRONG_SERVER_IDENTITY error:

   [HKEY_CLASSES_ROOT\APPID\helloservice.exe]
   "APPID"="{0bf52b15-8cab-11cf-8572-00aa00c006cf}"

NOTE: The bug mentioned in the paragraph above has been fixed in NT 4.0, Service Pack 2.

See the .reg file for information of the registry entries used by the service.

Many services are debugged by running them as console applications in the interactive user's identity. For example, this sample service can be debugged by running it as follows:

   helloservice -debug

1. To prevent CoRegisterClassObject failure, remove the following named value:

   [HKEY_CLASSES_ROOT\APPID\{0bf52b15-8cab-11cf-8572-00aa00c006cf}] LocalService"="HelloOleServerService"

2. To prevent IRunningObjectTable::Register(ROTFLAGS_ALLOWANYCLIENT) failure, do the following:

   Remove the following named value:

   [HKEY_CLASSES_ROOT\APPID\{0bf52b15-8cab-11cf-8572-00aa00c006cf}] "LocalService"="HelloOleServerService"

   and then add the following named value:

   [HKEY_CLASSES_ROOT\APPID\{0bf52b15-8cab-11cf-8572-00aa00c006cf}] "RunAs"="Interactive User"

   Make sure that you restore the modified registry entries after debugging.

To Compile

NT 4.0 or later is required. To compile, type:

   nmake

   nmake DEBUG=0

To Run

1. Change hello.reg to provide the full path of helloservice.tlb.

2. Register hello.reg in the registration database by double-clicking it.

3. Type helloservice -install to install the service. (NOTE: This will not run the service.)

4. Add INTERACTIVE to the DefaultAccessPermissions using the DCOMCNFG.EXE tool in the NT system32 directory. Make sure that INTERACTIVE is included in the DefaultLaunchPermissions. This allows the Visual Basic client in the interactive user's security context to access the service.

5. Use the Visual Basic file, vb.vbp, to control the object. Press the CoCreateInstance button to launch the service if required, and to create the object. Use the GetObject button to bind to a running object. GetObject can be used only if the service is already running. Use the GetMessage and SetMessage buttons to access the HelloMessage property, the SayHello button to invoke the SayHello method, and the CloseService button to invoke the Quit method to shut down the service. The service can also be configured using the Services control panel applet to run automatically when the system starts. It will be listed as “Hello OLE Server Service” in the Services applet.

6. helloservice -remove can be used to uninstall the service.

Files

SERVICE.C & SERVICE.H have the code to create a service and are copied from the SERVICE sample in the WIn32 SDK. (See the comments in service.h for information on command line arguments accepted by the service.)

MAIN.CPP and HELLO.CPP implement the automation object.

HELLOCF.CPP implements the class factory.

HELLO.ODL is the object description language that describes the property and methods that HELLO exposes.

TLB.H is the header file generated by MIDL.

MAKEFILE is the Makefile for project.

HELLO.REG is the Registry information.