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The LICSERVE sample introduces licensed components. LICSERVE modifies the COCruiseCar component of the DLLSERVE code sample and houses it as a licensed LicCruiseCar component in the LICSERVE.DLL COM server. This in-process server provides the components LicCruiseCar and LicCarSample. LicCarSample is the utility component that allows clients access to this server's logged behavior.
LICSERVE provides class factories for each of these components. The class factory for the LicCruiseCar component implements IClassFactory2, instead of the usual IClassFactory, to provide the licensing mechanism for this component. The LicCarSample component is not licensed and thus implements IClassFactory.
In the series of COM tutorial code samples, LICSERVE works with the LICCLIEN code sample to illustrate LICSERVE's COM server facilities for creating licensed components and supporting the subsequent manipulation of those components by the LICCLIEN.EXE client.
For functional descriptions and a tutorial code tour of LICSERVE, see the Code Tour section in LICSERVE.HTM. For details on setting up the programmatic usage of LICSERVE, see the Usage section in LICSERVE.HTM. To read LICSERVE.HTM, run TUTORIAL.EXE in the main tutorial directory and click the LICSERVE lesson in the table of lessons. You can also achieve the same thing by clicking the LICSERVE.HTM file after locating the main tutorial directory in the Windows Explorer. See also LICCLIEN.HTM in the main tutorial directory for more details on the LICCLIEN client application and how it works with LICSERVE.EXE itself. You must build LICSERVE.DLL before building or running LICCLIEN. LICSERVE's makefile automatically registers LICSERVE's components in the system registry. These components must be registered before LICSERVE is available to outside COM clients as a server for those components. This registration is done using the REGISTER.EXE utility built in the earlier REGISTER lesson. To build or run LICSERVE, you should build the REGISTER code sample first.
For details on setting up your system to build and test the code samples in this COM Tutorial series, see TUTORIAL.HTM. The supplied MAKEFILE is Microsoft NMAKE-compatible. To create a debug build, issue the NMAKE command in the Command Prompt window.
LICSERVE is a DLL that is meant to be used primarily as a licensed COM server. Though it can be implicitly loaded by linking to its associated .LIB file, it is normally used after an explicit LoadLibrary call, usually from COM's CoGetClassObject function. Servers like LICSERVE are registered in the registry. To use LICSERVE in a COM client program, a client does not need to include LICSERVE.H or link to LICSERVE.LIB. A COM client of LICSERVE obtains access solely through its components' CLSIDs and COM services. For LICSERVE, those CLSIDs are CLSID_LicCruiseCar and CLSID_LicCarSample. The LICCLIEN sample shows how this is done with the LicCruiseCar component that is licensed in the LICSERVE server.
The makefile that builds this sample automatically registers the server in the registry. You can manually initiate its self-registration by issuing the following command at the command prompt in the LICSERVE directory:
nmake register
This assumes that you have a compilation environment set up. If not, you can also directly invoke the REGISTER.EXE command at the command prompt while in the LICSERVE directory.
..\register\register.exe licserve.dll
These registration commands require a prior build of the REGISTER sample in this series, as well as a prior build of LICSERVE.DLL.
In this series, the makefiles use the REGISTER.EXE utility from the REGISTER sample. Recent releases of the Win32 Platform SDK and Visual C++® include a utility, REGSVR32.EXE, which can be used in a similar fashion to register in-process servers and marshaling DLLs.
The client sample and other related samples must be compiled before you can run the client. For more details on building the samples, see Building the Code Samples.
If you have already built the appropriate samples, LICCLIEN.EXE is the client executable to run for this sample. Click here to run LICCLIEN.EXE.
Depending on the security level of your browser you may see a dialog allowing you to either open the .EXE file or save it to disk. Click the "Open it" choice and then click the OK button.
Files Description
LICSERVE.TXT Short sample description.
MAKEFILE The generic makefile for building the LICSERVE.DLL
code sample of this tutorial lesson.
LICSERVE.H The include file for declaring as imported or defining as
exported the service functions in LICSERVE.DLL.
LICSERVE.CPP The main implementation file for LICSERVE.DLL. Has DllMain
and the COM server functions (for example, DllGetClassObject).
LICSERVE.DEF The module definition file. Exports server housing functions.
LICSERVE.RC The DLL resource definition file for the executable.
LICSERVE.LIC The license file for this licensed COM server.
LICSERVE.ICO The icon resource for the executable.
SERVER.H The include file for the server control C++ object. Also has
resource identifiers for resources stored in LICSERVE.DLL and
other extern declarations that are used internally within the
modules of LICSERVE.DLL.
SERVER.CPP The implementation file for the Server Control object.
FACTORY.H The include file for the server's class factory COM objects.
FACTORY.CPP The implementation file for the server's class factories.
CRUCAR.H The include file for the COLicCruiseCar COM object class.
CRUCAR.CPP The implementation file for the COLicCruiseCar COM object
class.
SAMPLE.H The include file for the COLicCarSample COM object class.
SAMPLE.CPP The implementation file for the COLicCarSample COM object
class.
This code sample is based on the code in the DLLSERVE lesson. This lesson begins with the COCruiseCar component studied in DLLSERVE lesson and modifies it into a licensed component, COLicCruiseCar, which is housed in the LICSERVE server. The bulk of this work is done in the class factory, where the IClassFactory2 interface is implemented instead of the usual IClassFactory interface. COLicCruiseCar is an aggregatable COM object that also aggregates the COCar COM object provided by the in-process server DLLSERVE. The LICSERVE in-process server uses this unlicensed COM object from another in-process server to provide the licensed COLicCruiseCar component to outside clients. The next lesson, LICCLIEN, illustrates just such a client.
LICSERVE also provides the necessary utility COM object, COLicCarSample, to permit trace logging of behavior inside LICSERVE components to appear in the client's trace logging display.
The main objective of the LICSERVE and LICCLIEN code samples is to show the mechanisms required to license and verify licensing of a component (LicCruiseCar).
LICSERVE uses many of the utility classes and services provided by APPUTIL. For more details on APPUTIL, study the APPUTIL library's source code in the sibling APPUTIL directory and APPUTIL.HTM in the main tutorial directory.
Like the DLLSERVE server, LICSERVE is self-registering. See the DLLSERVE lesson for more details on this process. For LICSERVE, the code for self-registration is in the DllRegisterServer and DllUnregisterServer functions in LICSERVE.CPP. Two new components are registered, CLSID_LicCruiseCar and CLSID_LicCarSample. These CLSIDs are defined in the global CARGUIDS.H in the \INC sibling directory.
In this lesson we'll concentrate on what it takes to license the COLicCruiseCar component. Other aspects of this code sample are very much the same as the DLLSERVE code sample.
We start the tour in LICSERVE.CPP. There is nothing significantly different with the DllGetClassObject and DllCanUnloadNow functions that were studied in DLLSERVE. However, there is something significantly new in the DLL_PROCESS_ATTACH case of the DllMain function. Here is DllMain:
BOOL WINAPI DllMain(
HINSTANCE hDllInst,
DWORD fdwReason,
LPVOID lpvReserved)
{
BOOL bResult = TRUE;
// Dispatch this main call based on the reason it was called.
switch (fdwReason)
{
case DLL_PROCESS_ATTACH:
// The DLL is being loaded for the first time by a given process.
// Perform per-process initialization here. If the initialization
// is successful, return TRUE; if unsuccessful, return FALSE.
bResult = FALSE;
if (UnicodeOk())
{
// Instantiate the CServer utility class.
g_pServer = new CServer;
if (NULL != g_pServer)
{
// Remember the DLL Instance handle.
g_pServer->m_hDllInst = hDllInst;
// Create a MsgBox object.
g_pServer->m_pMsgBox = new CMsgBox;
if (NULL != g_pServer->m_pMsgBox)
{
// Check for valid Machine License.
g_pServer->CheckLicense();
bResult = TRUE;
}
}
}
break;
case DLL_PROCESS_DETACH:
...
break;
case DLL_THREAD_ATTACH:
...
break;
case DLL_THREAD_DETACH:
...
break;
default:
break;
}
return (bResult);
}
The significant difference here is the g_pServer->CheckLicense call. CheckLicense is a new licensing-related method of the server control object (CServer). Here is what the CServer class declaration in SERVER.H looks like with added support for license management.
class CServer
{
public:
CServer(void);
~CServer(void);
void Lock(void);
void Unlock(void);
void ObjectsUp(void);
void ObjectsDown(void);
BOOL CheckLicense(void);
// A place to store the handle to loaded instance of this DLL module.
HINSTANCE m_hDllInst;
// A place to store a client's parent window.
HINSTANCE m_hWndParent;
// A Pointer to a Message Box object.
CMsgBox* m_pMsgBox;
// Global DLL Server living Object count.
LONG m_cObjects;
// Global DLL Server Client Lock count.
LONG m_cLocks;
// The Machine License key string for the LICSERVE server.
CHAR m_szLicenseKey[MAX_LICENSEKEY];
// Length of the global g_szLicenseKey string.
UINT m_cLicenseLen;
// Machine license verified.
BOOL m_bLicensed;
};
The CheckLicense method returns TRUE if the license was verified and FALSE if not. An ASCII m_szLicenseKey string is defined to contain a unique license key string that is hard-coded for this server. This key string provides what is called the machine license for the server. In this scheme, the entire server is licensed for use on the machine through this one key. For those components housed within the server that you want to license, you implement their class factories using IClassFactory2. We'll look at this shortly.
The key string is initialized in the CServer::CServer constructor (in SERVER.CPP) as follows:
CServer::CServer(void)
{
// Init the Server License Key string.
lstrcpyA(
m_szLicenseKey,
"LICSERVE 1.0 - Component Server - Copyright 1996-1997 Microsoft Corp.");
// Zero the Object and Lock counts for this attached process.
m_cObjects = 0;
m_cLocks = 0;
return;
}
We force the use of the ASCII lstrcpyA function because the key string is specified in CServer as a CHAR ASCII string and not as a more general TCHAR, which would compile to either Unicode or ANSI. This reliance on ASCII is merely a convenience, since the license file (where the matching license key string should be found, in this case LICSERVE.LIC) is also provided by us--the builders of this server--as part of the server. We control the format of the license file. To read an ASCII text file and match two ASCII text strings is easy. However, we could make the license key a Unicode or even an encrypted binary sequence if we were so inclined.
The internal license key used in this code sample is chosen to match the first text line of an outside ASCII text file. Here is that entire LICSERVE.LIC text file.
LICSERVE 1.0 - Component Server - Copyright 1996-1997 Microsoft Corp. Warning: This product is licensed to you pursuant to the terms of the license agreement included with the original software, and is protected by copyright law and international treaties. Unauthorized reproduction or distribution may result in severe civil and criminal penalties, and will be prosecuted to the maximum extent possible under the law.
If this file's copyright line is tampered with in any way, or if the file is absent, the server's class factories won't create any instances of their respective components. The presence of this file constitutes a machine license for the LICSERVE comonents. We'll explore this idea in more detail later.
CServer also has two other new data members, m_cLicenseLen and m_bLicensed. They are for later use by the various license-related methods in the server. CServer::CheckLicense assigns both of these values. Here is CheckLicense (in SERVER.CPP):
BOOL CServer::CheckLicense(void)
{
TCHAR szPath[MAX_PATH];
CHAR szLicKeyRead[MAX_LICENSEKEY];
UINT cbRead;
ULONG cbWasRead;
UINT cb;
HANDLE hFile;
// Assume license not verified to start.
m_bLicensed = FALSE;
// Assume the license key string is ASCII and count its length.
m_cLicenseLen = cb = lstrlenA(m_szLicenseKey);
// Get the module path. Then parse and replace DLL extension with LIC.
MakeFamilyPath(m_hDllInst, szPath, TEXT(LICENSE_FILE_EXT));
// Open the xx.LIC file and read in and check the license key for
// a match.
hFile = CreateFile(
szPath,
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (INVALID_HANDLE_VALUE != hFile)
{
cbRead = cb * sizeof(CHAR);
ReadFile(hFile, szLicKeyRead, cbRead, &cbWasRead, NULL);
CloseHandle(hFile);
if (cbRead == cbWasRead)
if (0 == memcmp(m_szLicenseKey, szLicKeyRead, cb))
m_bLicensed = TRUE;
}
LOGF1("P: CServer::CheckLicense. bLicensed=%i.", m_bLicensed);
return m_bLicensed;
}
CheckLicense first calculates the length of the internally held license key string and assigns it to m_bLicenseLen for later use. It then calls APPUTIL's MakeFamilyPath function to construct the path name to the LICSERVE.LIC license file. It calls the CreateFile function to open this license file for reading. If successful, it calls the ReadFile function to read a series of bytes from the front of the file. The number of bytes read is equal to the length of the internally stored license key string (the length assigned above to m_cLicenseLen). This program logic assumes that a copy of the internally held license key is stored at the beginning of the LICSERVE.LIC file. The call to memcmp, a C standard library function, compares the internal license key with the one read from the .LIC file.
If the two license key strings match, m_bLicensed is set to TRUE. If they do not, m_bLicensed is FALSE. The m_bLicensed Boolean variable specifies if the server module has verified the presence of the machine license file and is used by licensing functionality in the server (for example, the class factories). We will see how this variable is used later in this code tour.
Class factories are where the core of the licensing mechanism resides. For those components we want to protect with a license in this server, we implement IClassFactory2 instead of IClassFactory in their class factory. In this server we are protecting only one component, COLicCruiseCar. Here is the class factory declaration for the class factory CFLicCruiseCar in FACTORY.H:
class CFLicCruiseCar : public IUnknown
{
public:
// Main Object Constructor & Destructor.
CFLicCruiseCar(IUnknown* pUnkOuter, CServer* pServer);
~CFLicCruiseCar(void);
// A general method for initializing a newly created CFLicCruiseCar.
HRESULT Init(void);
// IUnknown methods. Main object, non-delegating.
STDMETHODIMP QueryInterface(REFIID, PPVOID);
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);
private:
// A private unconditional create for LicCruiseCar.
STDMETHODIMP CreateLicCruiseCar(IUnknown*, REFIID, PPVOID);
// We declare nested class interface implementations here.
// We implement the IClassFactory2 interface on this LicCruiseCar
// Class Factory to license these COM objects.
class CImpIClassFactory : public IClassFactory2
{
public:
// Interface Implementation Constructor & Destructor.
CImpIClassFactory(
CFLicCruiseCar* pBackObj,
IUnknown* pUnkOuter,
CServer* pServer);
~CImpIClassFactory(void);
// IUnknown methods.
STDMETHODIMP QueryInterface(REFIID, PPVOID);
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);
// IClassFactory methods.
STDMETHODIMP CreateInstance(IUnknown*, REFIID, PPVOID);
STDMETHODIMP LockServer(BOOL);
// IClassFactory2 methods.
STDMETHODIMP GetLicInfo(LPLICINFO);
STDMETHODIMP RequestLicKey(DWORD, BSTR*);
STDMETHODIMP CreateInstanceLic(
IUnknown*,
IUnknown*,
REFIID,
BSTR,
PPVOID);
private:
// Data private to this interface implementation of IClassFactory.
ULONG m_cRefI; // Interface Ref Count (debug).
CFLicCruiseCar* m_pBackObj; // Parent Object back pointer.
IUnknown* m_pUnkOuter; // Outer unknown for Delegation.
CServer* m_pServer; // Server Control Object.
};
// Make the otherwise private and nested IClassFactory interface
// implementation a friend to COM object instantiations of this
// selfsame CFLicCruiseCar COM object class.
friend CImpIClassFactory;
// Private data of CFLicCruiseCar COM objects.
// Nested IClassFactory implementation instantiation.
CImpIClassFactory m_ImpIClassFactory;
// Main Object reference count.
ULONG m_cRefs;
// Outer unknown (aggregation & delegation). Used when this
// CFLicCruiseCar object is being aggregated. Otherwise it is used
// for delegation if this object is reused via containment.
IUnknown* m_pUnkOuter;
// Pointer to this component server's control object.
CServer* m_pServer;
};
A CreateLicCruiseCar method is provided as an internal unconditional create function. This method creates a new COLicCruiseCar object regardless of any licensing conditions. It is conditionally called from two different license-aware creation methods, CreateInstance and CreateInstanceLic.
The IClassFactory interface is implemented as the nested class CImpIClassFactory, a pattern that should be familiar by now. As noted above, the CImpIClassFactory implementation is derived from IClassFactory2. Thus it must implement three methods (GetLicInfo, RequestLicKey, and CreateInstanceLic) in addition to the usual IClassFactory methods CreateInstance and LockServer. The rest of this CFLicCruiseCar class factory declaration is essentially the same as that presented in the DLLSERVE code sample's CFCruiseCar class factory. The CFCruiseCar::QueryInterface does one thing worthy of comment.
STDMETHODIMP CFLicCruiseCar::QueryInterface(
REFIID riid,
PPVOID ppv)
{
HRESULT hr = E_NOINTERFACE;
*ppv = NULL;
if (IID_IUnknown == riid)
{
*ppv = this;
LOG("P: CFLicCruiseCar::QueryInterface. 'this' pIUnknown returned.");
}
else if (IID_IClassFactory == riid)
{
*ppv = &m_ImpIClassFactory;
LOG("P: CFLicCruiseCar::QueryInterface. pIClassFactory returned.");
}
else if (IID_IClassFactory2 == riid)
{
*ppv = &m_ImpIClassFactory;
LOG("P: CFLicCruiseCar::QueryInterface. pIClassFactory2 returned.");
}
if (NULL != *ppv)
{
// We've handed out a pointer to the interface so obey the COM rules
// and AddRef the reference count.
((LPUNKNOWN)*ppv)->AddRef();
hr = NOERROR;
}
return (hr);
}
Since IClassFactory2 is derived from abstract base class IClassFactory, if we implement IClassFactory2 we must also implement IClassFactory methods. If QueryInterface requests either the IClassFactory or IClassFactory2 interface, we can safely return the same pointer, the one to the IClassFactory2 interface implementation.
We next turn to the implementations of the licensing-aware class factory methods. Here is the IClassFactory CreateInstance method in FACTORY.CPP.
STDMETHODIMP CFLicCruiseCar::CImpIClassFactory::CreateInstance(
IUnknown* pUnkOuter,
REFIID riid,
PPVOID ppv)
{
HRESULT hr = CLASS_E_NOTLICENSED;
if (g_pServer->m_bLicensed)
hr = m_pBackObj->CreateLicCruiseCar(pUnkOuter, riid, ppv);
else
{
LOG("P: CImpIClassFactory::CreateInstance. No Machine License.");
g_pServer->m_pMsgBox->ErrorID(IDS_NOLICENSE);
}
return hr;
}
The unconditional CreateLicCruiseCar function is called only if CheckLicense previously set m_bLicensed to TRUE when the server was first initialized for a given process. If the machine license was not verified, CheckLicense displays an error message indicating to the user that the client application is attempting to run with a component that is not licensed for use on this machine.
GetLicInfo is one of the methods required by IClassFactory2:
STDMETHODIMP CFLicCruiseCar::CImpIClassFactory::GetLicInfo(
LPLICINFO pLicInfo)
{
HRESULT hr = NOERROR;
LOG("P: CFLicCruiseCar::CImpIClassFactory::GetLicInfo.");
if (NULL != pLicInfo)
{
pLicInfo->cbLicInfo = sizeof(LICINFO);
// Inform whether RequestLicKey will work.
pLicInfo->fRuntimeKeyAvail = g_pServer->m_bLicensed;
// Inform whether the standard CreateInstance will work.
pLicInfo->fLicVerified = g_pServer->m_bLicensed;
}
else
hr = E_POINTER;
return hr;
}
This method writes appropriate values to the LICINFO structure whose address is passed in the pLicInfo parameter. The two important values in this structure are fRuntimeKeyAvail and fLicVerified. The fRuntimeKeyAvail member is set to the value that was returned by CheckLicense. This flag indicates in advance whether the RequestLicKey method can be attempted. If the server found no machine license, it will not (and should not) provide the internal license key to any caller of the RequestLicKey method. The fLicVerified member indicates whether the server verified that there is at least a machine license for the server.
Here is the IClassFactory2 RequestLicKey method (again in file FACTORY.CPP).
STDMETHODIMP CFLicCruiseCar::CImpIClassFactory::RequestLicKey(
DWORD dwReserved,
BSTR* pbstrKey)
{
HRESULT hr = CLASS_E_NOTLICENSED;
OLECHAR szLicKey[MAX_LICENSEKEY];
LOG("P: CFLicCruiseCar::CImpIClassFactory::RequestLicKey.");
// Only return the license key if the server machine license was
// verified.
if (g_pServer->m_bLicensed)
{
// Convert our ANSI license string to Wide Char and then alloc as
// a BSTR.
mbstowcs(szLicKey, g_pServer->m_szLicenseKey,
g_pServer->m_cLicenseLen); *pbstrKey = SysAllocString(szLicKey);
hr = (NULL != *pbstrKey) ? NOERROR : E_OUTOFMEMORY;
}
return hr;
}
RequestLicKey returns the license key in the form of a BSTR. In 32-bit COM, these basic strings are like zero-terminated Unicode strings, except that they are preceded by a DWORD value indicating the length of the string. BSTR variables are used heavily in OLE Automation and have come to us from Microsoft Visual Basic®. COM/OLE provides a set of API functions to manipulate these BSTRs, such as the SysAllocString call above. There is also a matching SysFreeString function that must be called to free these allocated BSTRs.
The RequestLicKey method is used to request a run-time license key from the server. The idea is that during development, the developer (or a development tool) can request from the server a copy of its internal license key. This request can succeed only if there is already a machine license with the server. Once obtained, the license key copy can be stored persistently for use by a client application that uses and ships with the server. Later, the client application can use this persistently stored license key to create a licensed component by calling the CreateInstanceLic method, which accepts the key as an argument.
The client application can succeed at this even if the machine license file does not accompany the server. In this situation, the normal call to IClassFactory::CreateInstance would fail, but a call to IClassFactory2::CreateInstanceLic would succeed.
Here is the IClassFactory2 CreateInstanceLic method in FACTORY.CPP.
STDMETHODIMP CFLicCruiseCar::CImpIClassFactory::CreateInstanceLic(
IUnknown* pUnkOuter,
IUnknown* pUnkReserved,
REFIID riid,
BSTR bstrKey,
PPVOID ppvCob)
{
HRESULT hr;
BOOL bMatch = FALSE;
BSTR bstrTemp;
UINT cch = g_pServer->m_cLicenseLen;
OLECHAR szLicKey[MAX_LICENSEKEY];
*ppvCob = NULL;
// Convert our ANSI license string to Wide Char and then alloc as BSTR.
mbstowcs(szLicKey, g_pServer->m_szLicenseKey, cch);
bstrTemp = SysAllocString(szLicKey);
if (NULL != bstrTemp)
{
if (NULL != bstrKey)
bMatch = (0 == memcmp(bstrTemp, bstrKey, cch * sizeof(OLECHAR)));
SysFreeString(bstrTemp);
if (bMatch)
hr = m_pBackObj->CreateLicCruiseCar(pUnkOuter, riid, ppvCob);
else
{
LOG("P: CImpIClassFactory::CreateInstanceLic. No Runtime License.");
g_pServer->m_pMsgBox->ErrorID(IDS_NORUNLICENSE);
hr = CLASS_E_NOTLICENSED;
}
}
else
hr = E_OUTOFMEMORY;
return hr;
}
The license key is passed as a BSTR, so we convert the internal license key string to a BSTR and then compare the two. If there is a match, we have a run-time license and can create an instance of the COLicCruiseCar and pass back the requested interface on it. If there is not a match, an error message is displayed to inform the user that the component is not licensed for run-time use.
What we've seen so far is that when the server DLL is attached to a process, it checks for the presence of the machine .LIC license file and tries to match its internal key to the key in the license file. If a match is found, the CFLicCruiseCar class factory will permit a normal call to IClassFactory::CreateInstance. Otherwise, it won't. In this tutorial sample, if the machine license is found, the client can also call IClassFactory2::RequestLicKey to obtain a copy of the internal license key. It can store this run-time license key to later create an instance by calling the IClassFactory2::CreateInstanceLic method. In actual applications the client would not call RequestLicKey. This call would be used during development only to obtain the run-time license key for the component in the server.
Run-time licensing is intended for component servers that are purchased in binary form by a developer and resold with the developer's client application. During development, the developer uses some tool that acts as a temporary client of the licensed component and calls IClassFactory2::RequestLicKey to obtain the run-time license key. This call would succeed because a machine license for the component would be present as part of the development kit purchased by the developer for the component. The developer would then use the run-time license key value in compiling the retail client application.
In a typical licensing scheme, the run-time key value is compiled into the client executable and used at run-time in calls to IClassFactory2::CreatInstanceLic. Then, when the retail client application is later sold by the developer in a package with the accompanying server component, the machine license file is not included in the package. In this case, only the client with the proper built-in, run-time license key will work with the resold component. This protects the component vendor from unauthorized copies of the component working with any client application that can call the component's IClassFactory::CreateInstance. Since the machine license file is absent, IClassFactory::CreateInstance will fail, returning error CLASS_E_NOTLICENSED.
Before leaving the class factories in FACTORY.CPP, we should note that an implementation of a CFLicCarSample factory is provided in a way very similar to what was studied in the DLLSERVE lesson. As before, this CarSample utility component is used to display trace logging of this server's behavior in the client's logging display and to provide an About dialog box from the server.
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