Re: Intermittent E_NOINTERFACE error, possibly RPC related

First you should try to reproduce it without the third party
software in the picture. If you reproduce it successfully,
it's time to contact MS tech support. If you can't, it's due
to either Symantec AV or Spysweeper, so try to find out
which one (might be caused by the combination). You'll
have to deal with their respective tech support departments
then.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Paul Baker [MVP, Windows - Networking]" <paulrichardbaker@xxxxxxxxxxxxxxxx>
wrote in message news:uRnG7%23bWHHA.4832@xxxxxxxxxxxxxxxxxxxxxxx
I am having an intermittent problem with DCOM.

I have a client application that calls a server application using DCOM. It
passes four interfaces. The server application calls those interfaces are
regular intervals, ie. calls back the client application. So technically
the client application is also a DCOM server.

Intermittently, the first call from the server application to the client
application returns E_NOINTERFACE without even entering the client
application code. It must be happening somewhere in the
DCOM/RPC/networking internals. Once this happens, all calls from the
server application to the client application consistently fail similarly
and repeatedly, even if both applications are restarted, until the client
is rebooted.

The client and server applications are running in console sessions under
the same user account. All threads involved entered a Multi-Threaded
Apartment (MTA), which simplifies things by eliminating the possibility
that something goofy is happening with STA and messages.

The client application runs on Windows XP Professional Service Pack 2 and
the server application runs on Windows Server 2003 Service Pack 1.

It happens an average of once a week and, each time, I have attempted to
do some research and debugging to learn more. I am now thinking it is more
network or RPC related than DCOM related. But I do not know what to look
for.

I discussed the possibility on microsoft.public.platformsdk.networking
that this is related to the 10 connection limit of Windows XP
Professional. This now seems doubtful as I wrote a test program that
stresses out my test machine (a similar setup) by connecting to it using a
file share and reading from and writing to a file at regular intervals. I
had 11 non-idle sessions going according to "net session". Any more
attempts to connect using the test program resulted in an error, usually
ERROR_REQ_NOT_ACCEP. Yet the DCOM server continued to function normally!

This is the output of "rpcping -s ncoantfs -v 3" when the error last
occured. "ncoantfs" is the name of the Windows XP Professional Service
Pack 2 machine. I ran it on of the Windows Server 2003 Service Pack 1
servers, named "ncoalink".

"RPCPing v2.12. Copyright (C) Microsoft Corporation, 2002
OS Version is: 5.2

Exception 5 (0x00000005)"

I do not know what exactly this means or how to determine the cause of
this apparent access denied error. It doesn't make sense to me that the
server would process tens of thousands of similar requests for days and
all of a sudden decide to poop out at seemingly random intervals.

All machines are running Symantec Anti-Virus Corporate Edition and
Spysweeper. There is a hardware-based firewall protecting our LAN that I
am told does not interfere with internal traffic (such as this).

I would appreciate any direction you can give me - thanks,

Paul



.

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