Established connections not expiring

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mreitano - 15 Feb 2005 15:28 GMT

Hi all - I've got a problem occurring at 2 out of about 25 clients I
have an app installed at. I've got a CAO over a tcp binary channel,
.net v1.1, win2k server and winNT6a clients (at least, the sites we
have issues with are WinNT clients). The CAOs are accessed from a VB6
client via COM interop.

We've had some issues with the remoting server using very large amounts
of RAM and eventually dying and noticed several clients had 40+
established connections to the server.

I've tried reproducing the problem every way I can think of in our test
environments and haven't had any luck - the application behaves well
and opens and closes 2 connections (with maybe 4-8 more TIME_WAIT
connections hanging out occasionally).

Has anyone seen a similar problem? Can anyone think of a reason (other
than a misbehaving client app) the client or server would hold onto
connections like that? I didn't even think it was possible... I've
seen various issues surrounding proxies or firewalls between client and
server, and I'm not sure what the network we're installed on is like
(in detail) but I haven't seen this problem.

Any help is appreciated.

-Matt

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mreitano - 15 Feb 2005 16:49 GMT

I've just got another netstat from a client - it looks like we've got
ESTABLISHED connections on the server where there are none on the
client. Several clients have a few (10+) FIN_WAIT_1 connections.
Seems like clients are waiting to shut down connections, not getting a
response from the server and shutting down locally, but the server is
never shutting down. Any thoughts?

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Sunny - 15 Feb 2005 16:58 GMT

> I've just got another netstat from a client - it looks like we've got
> ESTABLISHED connections on the server where there are none on the
> client. Several clients have a few (10+) FIN_WAIT_1 connections.
> Seems like clients are waiting to shut down connections, not getting a
> response from the server and shutting down locally, but the server is
> never shutting down. Any thoughts?

Do you use events?

Sunny

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mreitano - 15 Feb 2005 17:19 GMT

Nope. They're fairly basic objects. All they're really doing is some
basic data access and funneling serialized ADO26 recordsets down to the
client.

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Sunny - 15 Feb 2005 18:03 GMT

> Nope. They're fairly basic objects. All they're really doing is some
> basic data access and funneling serialized ADO26 recordsets down to the
> client.

Do you use client side sponsors to keep this CAO's alive?

Sunny

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mreitano - 15 Feb 2005 19:48 GMT

No - the lifetime of the objects is very short and we haven't (until
now, anyway) had any issues with the default lifetimes. They are
really only set up as CAO's in order to set a single property before
making a single call, and then the object is destroyed. The decision
to not use SAO's was based mostly on the fact that we had tons of
legacy VB6 code to deal with and it wasn't all so clean that we could
expect to change it to single calls without some problems.

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mreitano - 18 Feb 2005 18:55 GMT

Any other suggestions or ideas? I'm getting fairly desparate here.
Any ideas at all on how a connection could be orphaned on the server
side and think it's ESTABLISHED like that when the client has been
completely removed from the network?

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Sunny - 23 Feb 2005 16:26 GMT

> Any other suggestions or ideas? I'm getting fairly desparate here.
> Any ideas at all on how a connection could be orphaned on the server
> side and think it's ESTABLISHED like that when the client has been
> completely removed from the network?

Can you prepare a working example, which reproduces the problem? It's
really hard to understand what's going on.

You may try what kind of objects to pass between the server and the
client. Check if you do not send an MBR object from the client
(unintentional), etc.

Sunny

P.S. read this article about the short but complete program:
http://www.yoda.arachsys.com/csharp/complete.html

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mreitano - 24 Feb 2005 22:08 GMT

I wish I could build something simple to reproduce the issue. I'm
having a lot of trouble reproducing the problem in our test
environments and I don't have any leads for what the cause may be. I'm
going to spend some more time trying - maybe build out some more
automation and let it run for a few days to see if I can get the
problem to occur. Failing that I may go back to creating the objects
as SAO's and see if that helps. I'd rather they ran that way anyway.
If I find a solution, I'll post it here. Thanks for the help.

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Established connections not expiring

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