Microsoft KB Archive/305718

= PRB: Windows NT 4.0 Client Unable to Connect to CLB Component =

Article ID: 305718

Article Last Modified on 6/4/2003

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APPLIES TO

 Microsoft Application Center 2000 Standard Edition, when used with:  Microsoft Windows 2000 Standard Edition

 Microsoft Windows NT 4.0 

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This article was previously published under Q305718



SYMPTOMS
If a Windows NT 4.0-based computer (that is using a COM+ proxy stub) attempts to instantiate a COM+ component that is configured to use Application Center 2000's component load balancing (CLB) feature, the following error may occur.

Runtime error -2147022986 (80070776)

Automation Error:

The object exporter specified was not found



CAUSE
By default, Windows NT 4.0-based computers will attempt to use User Datagram Protocol (UDP) to establish a Distributed Component Object Model (DCOM) connection. In most cases, this connection will fail when you are connecting to a Windows 2000-based computer because Windows 2000 computers use Transmission Control Protocol (TCP) for DCOM connections. Once the connection attempt fails, the Windows NT 4.0 client will attempt to use the next configured DCOM protocol until a DCOM connection can be established.

If the target COM+ component is configured to use CLB, then the Windows NT 4.0 client will attempt to use UDP and will fail with the error noted in the &quot;Symptoms&quot; section. To instantiate COM+ components configured for CLB, the DCOM client must use TCP.

NOTE: Only Windows NT 4.0-based computers are effected by this problem.



RESOLUTION
The DCOM client determines the protocol used when the client is negotiating a DCOM connection. Therefore, the default protocols of DCOM on the Windows NT 4.0 client must be modified to use TCP.

To modify the default protocols of DCOM to use TCP, use the following procedure. Perform these steps on the Windows NT 4.0-based computer only. <ol> Open DCOMCNFG.</li> Navigate to the Default Protocols tab.</li> Arrange the protocols in the following order:

Connection-oriented TCP/IP

Connection-oriented SPX

Connection-oriented NetBEUI

Connection-oriented Netbios over IPX

</li> Click OK on the Distributed COM Configuration Properties property sheet.</li> Restart the computer to make the changes to take effect.</li></ol>

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STATUS
This behavior is by design in DCOM.

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Steps to Reproduce Behavior

 * 1) Create the COM+ proxy stub installation files from a CLB-enabled COM+ component.
 * 2) Using the installation files, install the COM+ proxy stub onto a Windows NT 4.0-based computer.
 * 3) Attempt to instantiate the component on the Windows NT 4.0 computer.

Keywords: kbprb KB305718

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