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DCOM95 1.3
Release Notes
Last Modified: March 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 since DCOM95 1.2
II. Bug Fixes since DCOM95 1.2
III. Known Issues
IV. Differences from DCOM on Windows NT
V. Redistribution
VI. Support & Resources
VII. File List
I. New Features since DCOM95 1.2
--------------------------------
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 since DCOM95 1.2
------------------------------
This section describes bugs fixed in DCOM95 1.3 that affected
applications running on Windows 95 with DCOM95 1.2 installed.
File Monikers Support Additional Path Syntax
File monikers can now be created out of arguments of the form
<startdir><relativepath>, 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.
Heap Memory Leak When Using IDataObject/IAdviseSink
There was a memory leak when using Uniform Data Transfer between
a data object on a local server that implements the IDataObject
interface and a client that implements IAdviseSink. When the
client used the STA model, every call would leak 32 bytes. This
problemmanifest itself as the server taking more and more time
to execute. The leak 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 youÆve 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 clientÆs 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. 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 does 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 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).
If you elect to redistribute DCOM95, you should include the files
DCOM95.EXE and optionally DCM95CFG.EXE on your distribution media.
You should run these self-extracting executables from your setup
program. These executables will install the correct files only if
a more recent version is not already installed. They write the
correct registry entries required by DCOM95. They do not install
anything on Windows NT.
By default, DCOM95.EXE and DCM95CFG.EXE display a EULA and other
prompts to the user. DCOM95.EXE prompts the user to reboot the
system on completion. If you run either executable from your setup
program, you may elect to run the self-extracting executables in
"silent" mode. You must prompt the user to reboot the system when
your setup program exits if DCOM95 has been installed.
To run either DCOM95.EXE or DCM95CFG.EXE in silent mode, use the command line:
[exe-name] /r:n /q:a
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.
asycfilt.dll 2.40.4275.1
comcat.dll 5.0.1601.1
compobj.dll 2.30.200.1
dcom2w98.dll 2.10.35.35
dllhost.exe 4.71.3328.0
iprop.dll 4.0.1381.6
ole2.dll 2.30.200.0
ole32.dll 4.71.3328.0
oleaut32.dll 2.40.4275.1
olecnv32.dll 4.71.3328.0
olepro32.dll 5.0.4275.1
olethk32.dll 4.71.3328.0
rpcltc1.dll 4.71.3328.0
rpcltc5.dll 4.71.3328.0
rpcltccm.dll 4.71.3328.0
rpclts5.dll 4.71.3328.0
rpcltscm.dll 4.71.3328.0
rpcmqcl.dll 4.71.3328.0
rpcmqsvr.dll 4.71.3328.0
rpcns4.dll 4.71.3328.0
rpcrt4.dll 4.71.3328.0
rpcss.exe 4.71.3328.0
secur32.dll 4.10.0.2177
stdole2.tlb 2.40.4275.1
stdole32.tlb 2.10.3027.1
storage.dll 2.30.200.0
This table lists the version numbers of files distributed with
DCM95CFG.
dcomcnfg.exe 5.00.1603.1
ciscnfg.exe 4.71.2618.0