DCOM95 1.3 Release Notes Last Modified: September 14, 1998 DCOM95 provides Distributed COM support for Microsoft® Windows® 95. The DCOM wire protocol transparently provides support for reliable, secure, and efficient communication between Component Object Model (COM) components such as ActiveX® controls, scripts, and Java applets residing on different machines in a LAN, a WAN, or on the Internet. With DCOM, your application can be distributed across locations that make the most sense to your customer and to the application. For more in-depth information, see the DCOM Technical overview available on the Microsoft COM home page, http://www.microsoft.com/com/. Contents ======== I. New Features II. Bug Fixes III. Known Issues IV. Differences from DCOM on Windows NT V. Redistribution VI. Support & Resources VII. File List I. New Features --------------- Replacing DCOM95 with Older Version Prohibited In previous releases of DCOM95, you could replace a newer version of DCOM95 with an older version of DCOM95. Version numbers are now checked on installation, and you are not permitted to install an older version over a newer version. This change will avoid problems with incompatible versions of DLLs. Visual Studio 6.0 Process Monitoring Support In support of Visual Studio 6.0, DCOM95 provides monitoring information for developers to help them understand the behavior, performance, and structure of their application. If you are using Visual Studio Analyzer on a computer that is running Windows 95, you should always use this version of DCOM95. New Directory Created by Setup Setup creates a directory called DCOM95 under your system directory. The end-user license agreement and other files are stored there. Setup also creates a subdirectory of DCOM95 called OLDOLE, into which the old DCOM95 or OLE binaries are backed up. These files are restored if you later uninstall DCOM95. COM Internet Services The COM Internet Services (CIS) enable clients and servers to be connected over the Internet using COM. CIS consists of * A new DCOM protocol, Tunneled TCP * A new moniker type, OBJREF moniker * A new CISCNFG utility For CIS client support in Windows 95, you must install both DCOM95 and DCOMCFG. Then use the CISCNFG tool, which is installed when you install the DCOM configuration utility, to change the registry key that defines which protocol to use for remote processes. In the Command Prompt window, enter: ciscnfg Where is: * rpc to use RPC * http to use HTTP * tcp_http to try TCP first and then, if the server times out, to try HTTP. The ciscnfg command with no argument provides usage information. No SDK updates are required to use the Tunneled TCP protocol. There are a few updates for OBJREF monikers. CreateObjrefMoniker Creates an OBJREF moniker based on a pointer to an object. WINOLEAPI CreateObjrefMoniker( LPUNKNOWN pUnk, //Pointer to the object LPMONIKER *ppMk //Address of pointer to OBJREF moniker ); Parameters pUnk Pointer to the IUnknown interface on the object that the moniker is to represent. ppMk Address of a pointer to the IMoniker interface on the OBJREF moniker created. Return Values This function supports the standard return values E_OUTOFMEMORY and E_UNEXPECTED, as well as the following: S_OK The OBJREF moniker was successfully created. Remarks Clients use OBJREF monikers to obtain a marshaled pointer to a running object in the server’s address space. The server typically calls CreateObjrefMoniker to create an OBJREF moniker and then calls IMoniker::GetDisplayName, and finally releases the moniker. The display name for an OBJREF moniker is of the form: OBJREF:nnnnnnnn Where nnnnnnnn is an arbitrarily long base-64 encoding that encapsulates the machine location, process endpoint, and interface pointer ID (IPID) of the running object. The display name can then be transferred to the client as text. For example, the display name can reside on an HTML page that the client downloads. The client can pass the display name to MkParseDisplayName, which creates an OBJREF moniker based on the display name. A call to the moniker’s IMoniker::BindToObject method then obtains a marshaled pointer to the running instance on the server. For example, a server-side COM component contained in an active server page can create an OBJREF moniker, obtain its display name, and write the display name to the HTML output that is sent to the client browser. A script that runs on the client side can use the display name to get access to the running object itself. A client-side Visual Basic script, for instance, could store the display name in a variable called strMyName and include this line: objMyInstance = GetObject(strMyName) The script engine internally makes the calls to MkParseDisplayName and IMoniker::BindToObject, and the script can then use objMyInstance to refer directly to the running object. If the running object uses static IPIDs and the server process always runs on the same computer at a well-known endpoint, the display name of the OBJREF moniker will always be the same. In that case, the server can store the display name instead of calculating it each time it receives a request for the object. IMoniker - OBJREF Moniker Implementation OBJREF monikers represent a reference to an object instance that is running on an out-of-process server, either locally or remotely. The moniker identifies the object instance and the computer the object is running on. An OBJREF moniker is similar in many ways to a pointer moniker, except that the running object is out-of-process. A client can call IMoniker::BindToObject on an OBJREF moniker and use the pointer it obtains to access the running object, regardless of its location. An important distinction from a pointer moniker is that the display name of an OBJREF moniker can be embedded in an HTML page, and the running object represented by the moniker can be bound by a client script, applet, or ActiveX control. When to Use The primary use for an OBJREF moniker is to obtain access to a running object instance over the Internet. An active server page or some other means of generating dynamic HTML content places the display name of an OBJREF moniker in a parameter to an applet or an ActiveX control. The code of the applet or control calls CreateObjrefMoniker to create an OBJREF moniker based on the display name, and it then calls IMoniker::BindToObject on the resulting OBJREF moniker to get access to the running object instance. The active server page then marshals a pointer to the running object back to the page’s client. Remarks IMoniker::BindToObject. For OBJREF monikers, the pmkToLeft parameter must be NULL. Because the OBJREF moniker represents a running object, no activation takes place. If the represented object is no longer running, BindToObject fails with E_UNEXPECTED. IMoniker::BindToStorage. This method obtains a marshaled pointer to the requested interface on the storage that contains the running object. Because the OBJREF moniker represents a running object, no activation takes place. If the represented object is no longer running, BindToStorage fails with E_UNEXPECTED. IMoniker::Reduce. This method returns MK_S_REDUCED_TO_SELF and passes back the same moniker. IMoniker::ComposeWith. If pmkRight is an anti-moniker, the returned moniker is NULL. If pmkRight is a composite whose leftmost component is an anti-moniker, the returned moniker is the composite with the leftmost anti-moniker removed. If pmkRight is neither an anti-moniker nor a composite moniker whose leftmost component is an anti-moniker, then the method checks the fOnlyIfNotGeneric parameter. If it is FALSE, the method combines the two monikers into a generic composite; if it is TRUE, the method sets *ppmkComposite to NULL and returns MK_E_NEEDGENERIC. IMoniker::Enum. This method returns S_OK and sets ppenumMoniker to NULL. IMoniker::IsEqual. This method returns S_OK if *pmkOther is an OBJREF moniker and the paths for both monikers are identical (using a case-insensitive comparison). Otherwise, the method returns S_FALSE. IMoniker::Hash. This method calculates a hash value for the moniker. IMoniker::IsRunning. Because OBJREF monikers represent a running object instance, this method returns TRUE unless the object is known to be no longer running because a recent call failed. The method ignores pmkToLeft. IMoniker::GetTimeOfLastChange. This method returns E_NOTIMPL. IMoniker::Inverse. This method returns an anti-moniker (i.e., the results of calling CreateAntiMoniker). IMoniker::CommonPrefixWith. If the two monikers are equal, this method returns MK_S_US and sets *ppmkPrefix to NULL. If the other moniker is not an OBJREF moniker, this method passes both monikers to the MonikerCommonPrefixWith function. This function correctly handles the case where the other moniker is a generic composite. If there is no common prefix, this method returns MK_E_. IMoniker::RelativePathTo. This method returns E_NOTIMPL. IMoniker::GetDisplayName. This method obtains the display name for the OBJREF moniker. The display name is a 64-bit encoding that encapsulates the machine location, process endpoint, and interface pointer ID (IPID) of the running object. For future compatibility, the display name is restricted to characters that can be specified as part of a URL. IMoniker::ParseDisplayName. If pmkToLeft is not NULL, this method returns MK_E_SYNTAX. IMoniker::IsSystemMoniker. This method returns S_OK and passes back MKSYS_OBJREFMONIKER. Support for VB6.0 Data Types Visual Basic® 6.0 allows Visual Basic variants to contain user- defined data structures. DCOM95 now supports remoting of these variants. II. Bug Fixes ------------- Race Condition When Unloading Multiple Modules When multiple modules were unloaded simultaneously, a race condition would occur in previous versions of DCOM95. Depending upon the order in which the modules were unloaded, an access violation could result. This has been corrected in this release of DCOM95. Desktop Unresponsive During RPC Protocol Negotiations Earlier versions of DCOM95 did not dispatch messages while they were negotiating RPC protocols. In certain cases, if the user launched another application during the time that RPC protocols were being negotiated, the machine would appear to be unresponsive. After 30 seconds, processing of messages would resume. This behavior has been changed in the latest release of DCOM95, and applications can be launched while RPC protocols are being negotiated. Desktop Unresponsive When New Application Launched RPC creates a hidden window in the Multiple-Threaded Apartment (MTA), which is not required to dispatch messages per DCOM spec. When a user launches a new application from the desktop, Windows sends a message to all other window handles, notifying them of this event, and expecting a reply. Under earlier versions of DCOM95, the hidden RPC window might not reply, and Windows would hang. This version of DCOM95 fixes this problem, and the RPC window no longer makes the desktop unresponsive when new applications are launched. Multiple IP Addresses Heap Corruption In certain situations, if you were running a previous version of DCOM95 on a machine with more than one IP address, the IP address buffer would be overrun and the heap would be corrupted. This has been fixed in the latest release of DCOM95. Only First IP Address Used If you were running a previous version of DCOM95 on a machine that had two network adapter cards (and therefore two IP addresses, each assigned to a different address card), DCOM95 would use only one network adapter. In this release of DCOM95, if the first one tried does not work, the second one will be used. RPC Now Tries Multiple IP Addresses When doing a remote procedure call to a machine with multiple IP addresses, subsequent IP addresses will now be tried if connecting to the first one fails. File Monikers Support Additional Path Syntax File monikers can now be created out of arguments of the form , such as "C:\bug\bug\..\..\foo.jpg." In DCOM95 1.1, only relative paths (e.g., "..\..\foo.jpg") or absolute paths (e.g., "C:\foo.jpg") were permitted. General Protection Fault When Oleaut32.dll Unloaded In previous versions of DCOM95, a general protection fault occurred when Oleaut32.dll was unloaded before a call to CoUninitialize. This would most often occur when a VB application created a control statically linked to Oleaut32.dll, and then freed the control prior to calling CoUninitialize. This no longer causes a general protection fault in the latest release of DCOM95. Visual Basic Type Marshaling and Unmarshaling The marshalling and unmarshaling of certain Visual Basic data types has been fixed. Array parameters with a size greater than 64K are now allowed. Structures defined using aliases to the type are now marshaled and unmarshaled correctly. Atoms Being Deleted Too Many Times in OleUninitialize This bug appeared in applications that call OleInitialize and OleUninitialize multiple times. During initialization, OLE adds many atoms for DDE RPC. If the atoms have already been added by another thread, they are not added again. However, during uninitialization, atoms were always deleted, and the handles were not nullified. Therefore, the next time OleInitialize was called, the old handles would still exist, even though the atoms were already deleted, and OLE would not add them again. This led to all OLE atoms being invalid after multiple calls to OleInitialize and OleUninitialize. This problem has been fixed in this release of DCOM95. ADO Servers Shut Down Properly Active Data Objects (ADOs) use pointer monikers to start a server process. Previous versions of DCOM95 contained a bug involving pointer moniker reference counting, whereby pointer monikers were created with an initial reference count of 1, rather than 0. Therefore, the reference count of the pointer moniker would never get to zero, and the pointer moniker would never be freed. As a result, ADO servers were never shut down, even after the last pointer to them had been released. This has been fixed in this release of DCOM95. CoCreateInstance Works with Own DNS Name In previous versions of DCOM95, calling CoCreateInstance with the fully qualified name of the local machine did not work. This has been fixed in the current version of DCOM95, and CoCreateInstance now correctly creates and instance on the local machine. Slow Commit On Root Storage With Very Large Compound File In previous versions of DCOM95, the commit time on a root storage opened in STGM_TRANSACTED mode became very slow as the compound file became very large (e.g. 400M). The internal page table limits have been increased, and this is no longer a problem. Exporting Objects From a Recreated MTA In previous versions of DCOM95, a server could not export an object from a Multi-Threaded Apartment (MTA) if this was not the first time the MTA had been created in the process. This has been fixed. Now, if a server creates an MTA, destroys it, and subsequently recreates the MTA, objects will be able to be exported from the MTA. Multiple Instances Of Visual Basic 4 EXEs In DCOM95 v1.1, if you started multiple instances of the same Visual Basic 4 executable, then shut them down in any order but LIFO (Last-In First-Out), the last exe would hang. This was also true of E-Forms in Microsoft Exchange. This has been fixed in the latest release of DCOM95. You may now shut down Visual Basic 4 exes in any order. Extended Characters in Visual Basic File Names If you named a Visual Basic module or class using extended characters for a given language, that file might not open on machines configured for a different locale. This has been fixed. III. Known Issues ----------------- Corel WordPerfect Suite 7: Installation Causes Invalid Page Fault If you install Corel WordPerfect Suite 7 on a Windows 95 system running DCOM95, you may get an invalid page fault in PfOd70.pfc during installation. If this error appears, just close the error message dialog box. Setup should continue successfully. Microsoft Access95: Database Replication Does Not Work If you try to replicate an Access database using Microsoft Access 95 on machines with DCOM95 installed, you may get the following error message: Microsoft Access cannot complete this operation because it can't find or initialize the dynamic-link library Msjtrclr. This is a problem in Microsoft Access 95. You may work around this issue by writing a program which uses the Access object model rather than the replica tool, or by using the briefcase for replication. Microsoft Access 97 is not affected by this issue. WordPerfect If you have a WordPerfect document containing an embedded Corel spreadsheet and the spreadsheet contains another embedded object (for example, a bitmap), you may get a warning dialog saying you’ve lost the network connection when you close the innermost object. There may be four or five such warnings. All these warnings are benign. Just close them and continue. Multiple-threaded apartment (MTA) clients that use BSTR conversion routines may block DDE messages Automation BSTR conversion routines (for example, BstrFromR4) create hidden windows to facilitate the type conversion. These windows do not service the Windows message queue. If such a window is created from within an MTA client, DDE messages may be blocked. The client thread has no obligation to service the message queue under the MTA programming model. If it does not, this top-level window causes global broadcast messages to block. There are two ways to work around this situation. Either call the BSTR conversion routines from within a single-threaded apartment (STA) client, or make the client’s MTA thread behave like an STA thread. (An STA thread must service the message queue.) If the thread is blocking on a win32 handle, it must call the MsgWaitForMultipleObjects function to simultaneously dispatch Windows messages. DLL path names longer than 127 characters cause error If you register a DLL with a path name of 128 characters or longer, the registration will succeed, but CoCreateInstance or CoGetClassObject will return an error (REGDB_E_CLASSNOTREG) when accessing an object supported by this DLL. IV. Differences from DCOM on Windows NT --------------------------------------- Security Capabilities of DCOM95 The core functionality and application programming interface (API) for DCOM95 are identical in both Windows 95 and Windows NT 4.0/5.0. However, certain capabilities related to security are different because of the different security infrastructures of the operating systems. Using the default security settings of the system is recommended; it is also necessary to enable "user-level" security on file-system shares. (See below.) The following services, which can be used to override default security, are available: * CoInitializeSecurity * CoQueryAuthenticationService * CoQueryProxyBlanket * CoSetProxyBlanket * CoQueryClientBlanket * IClientSecurity Interface * IServerSecurity Interface However, certain capabilities that are part of DCOM for Windows NT will not be available on Windows 95 because of differences in the security infrastructure on Windows 95. In particular, the lack of security functions in the Win32 API, such as the ability to create access control lists (ACLs), and the AccessCheck function, as well as the lack of a security context associated with thread and process tokens, should be taken into account. Windows 95 do not natively support these functions or constructs. Because of this, DCOM95 will not support impersonation (specifically, the CoImpersonateClient and CoRevertToSelf helper functions over the IServerSecurity interface), which is based on thread- and process-token security in Windows NT 4.0. Impersonation is commonly used to automatically control access to restrictable system resources such as the file system, other processes, and the network. These resources are not restrictable on Windows 95. DCOM95 does, however, offer programmers various helper objects to provide ACL and access-check functionality, which can be used to explicitly control access by remote clients to both system and user-defined resources or data. These helper objects are provided by the system object CLSID_DCOMAccessControl, which implements the IAccessControl interface. IAccessControl should be used to manage security permissions programmatically wherever portability between Windows 95/98 and Windows NT is a concern. The CLSID_DCOMAccessControl object is available in all releases of DCOM95 and in Windows NT 4.0 SP2 or later. For details about IAccessControl, see the Platform SDK documentation. Launch and Access Security Controlling who can launch server-class code is not supported in DCOM95, because launching servers is not supported. Servers/classes must already be running in order for remote clients to connect to them and make use of their services. DCOM95 does support the ability to connect to already running classes/servers. Access security is supported via the \APPID\{.}\AccessPermissions registry key and adjusted via the DCOMCNFG tool or during installation or setup of the server code. Unauthenticated users will be able to use servers if you configure the class to support unauthenticated connections (through static configuration tools or dynamically via the CoInitializeSecurity function). You can also build arbitrary ACLs to define which users and groups can access specific services. Authentication Levels DCOM95 clients can make DCOM calls using any authentication level. DCOM95 servers or clients receiving callbacks can accept only DCOM calls using RPC_C_AUTHN_LEVEL_NONE or RPC_C_AUTHN_LEVEL_CONNECT authentication levels. Transports DCOM95 supports only TCP connectivity. If you do not have the TCP/IP protocol installed, DCOM95 will not be able to support cross-machine COM. Registry Settings The following registry keys found under HKEY_LOCAL_MACHINE\Software\Microsoft\OLE are established by DCOM95: EnableDCOM (default value = "Y"). Enables DCOM on this machine. When set to "N", the machine is prevented from connecting to or activating objects on remote machines, and remote machines are unable to connect to objects on the local machine. Setting this value to "Y" enables either connectivity as a client to remote objects (when EnableRemoteConnect='N', as explained below), or full client/server connectivity (when EnableRemoteConnect='Y', as explained below). EnableRemoteConnect (default value = "N"). Enables COM servers to support remote clients. When this value is set to "Y", references to interfaces on local objects can be passed to remote clients, and remote clients are allowed to connect to running objects. When this value is set to "N", this machine is allowed to connect to remote objects but cannot act as a server: the machine is prevented from connecting to running objects. In addition, the following registry key is found under HKEY_CLASSES_ROOT\CLSID: {bdc67890-4fc0-11d0-a805-00aa006d2ea4}\InstalledVersion. Contains the version number of DCOM95 in the format "a,b,c,d". This value can be used by Internet Component Download to determine whether DCOM95 is installed. This value is added to the registry during setup and should not be modified. Using Windows 95 as a remote server host Windows 95 can be a remote server host, with the following caveats: * There is no launch capability. The server process must be already running for a client to connect to it. * If secure connections are needed, the server (and in the case of callbacks, the client) must have user-level access control with the name of a security provider set. * The registry value "EnableRemoteConnect" must be set to "Y". DCOM95 has been tested most extensively using the Windows NT Domain security provider. You may encounter problems using other security providers. To establish user-level access control, you must have Filesec.vxd installed. This file is generally installed on Windows 95 machines when you install file and print sharing. To enable user-level access control, open the Network dialog box in Control Panel, click the Access Control tab, check the box marked User-level Access Control, and enter the name of your security domain. This may affect the way you currently share directories on the network from your computer; see the online documentation for details. If you do not have an Access Control tab in your network configuration control panel, you need to install a network client service. Click the Network clients, setting up entry in the online help index for information on installing a network client. V. Redistribution ----------------- For information about redistributing DCOM95, please review the redistribution guidelines contained in the end-user license agreement (license.txt). VI. Support & Resources ----------------------- Paid Support DCOM95 application development is supported by Microsoft Technical Support. You can ask questions through your Premier Level support contract. You can also ask questions through your Priority Level contract or purchase individual Priority Support incidents (essentially a one-time fee for one question). If you would like to understand more about Microsoft's paid support options, you can call Microsoft Support Sales at (800) 936-3500 from 6:00 a.m. to 6:00 p.m. Pacific time, Monday through Friday, excluding holidays. Please note that technical support is not available through this number. Microsoft Technical Support Information is also available on the World Wide Web at http://www.microsoft.com/support/. Free Support Newsgroups are a great place for free peer support. As time and resources allow, Microsoft developers, program managers, support engineers, and test engineers visit the site to collect feedback and answer questions or correct misperceptions. There is no guarantee that you will receive a response from Microsoft to any newsgroup posting. The following newsgroups can be used to ask questions about DCOM95: * comp.os.ms-windows.programmer.ole * microsoft.public.win32.programmer.ole The DCOM mailing list is another good form of free peer support. An advantage to being on a mailing list is that this is where Microsoft will make early announcements of information on a given topic. Again, it is peer support, and Microsoft staff will often lurk there, but are not guaranteed to respond to any postings. To learn more about the DCOM mailing list, please review our Mailing List page, http://www.microsoft.com/sitebuilder/resource/mail.asp. Providing Feedback Please send any comments or bug reports to the DCOM mailing list. Resources You can find additional information about DCOM on the COM Home Page at http://www.microsoft.com/com/. VII. File List -------------------- This table lists the version numbers of files distributed with DCOM95. oleaut32.dll 2.40.4275 secur32.dll 4.10.1999 compobj.dll 2.3.2 ole2.dll 2.3.2 ole32.dll 4.71.2900 olecnv32.dll 4.71.2900 olethk32.dll 4.71.2900 rpcltc1.dll 4.71.2900 rpcltc5.dll 4.71.2900 rpcltccm.dll 4.71.2900 rpclts5.dll 4.71.2900 rpcltscm.dll 4.71.2900 rpcns4.dll 4.71.2900 rpcrt4.dll 4.71.2900 rpcss.exe 4.71.2900 storage.dll 2.3.2 stdole2.tlb 2.40.4275 stdole32.tlb 2.1 imagehlp.dll 4.00 dllhost.exe 4.71.2900 comcat.dll 5.0 iprop.dll 4.00 rpcmqcl.dll 4.71.2900 rpcmqsvr.dll 4.71.2900 olepro32.dll 5.0.4275 asycfilt.dll 2.40.4275 dcom2w98.dll 2.10.35.35 This table lists the version numbers of files distributed with DCM95CFG. dcomcnfg.exe 5.00.1603.0 ciscnfg.exe 4.71.2618