[Nut-upsuser] Upsmon and Winnut disconnect regularly

stevesz at enternet.hu stevesz at enternet.hu
Sat Dec 29 09:06:30 UTC 2007

On Fri, 28 Dec 2007 09:42:19 -0500, "Charles Lepple" <clepple at gmail.com>
> On Dec 28, 2007 6:19 AM,  <stevesz at enternet.hu> wrote:
>> This time I'm using Nut 2.2.0, Debian etch and kernel v.
>> My hardware config is quite simple. There are 2 PCs connected to my
>> PowerMust 600VA. One is mensioned above the other is a Windows PC
>> using Winnut 2.0.0b. The Linux PC is connected to the UPS via a
>> serial cable and acts as the server.
> How are the Linux PC and Windows PC connected on the network side? Is
> it just via a switch, or is there another device in between, like a
> firewall? Are there any software firewalls involved?

They are connected just via a switch with a few meters of cable.

>> The problem is that both upsmon and winnut disconnect regularly but
>> in random moments. First I've been using kernel v. and
>> tried upgrading it to the version mensioned, but I've reached the
>> same results. Remembering that I've been using Nut 2.0.0 succesfully
>> a few years ago, I've tried that version again, but with the same
>> results. Then I realized that I've been using kernel v. 2.6.10 that
>> time, so there can be some problems.
>> I've analized the network traffic between the two PCs and realized
>> that maybe I have problems with the delayed ACKs. And at this point
>> I have no idea how to continue.
> I am not 100% sure, but I don't believe that NUT does anything special
> for TCP connections. So in theory, you should see the same sorts of
> problems on any service that keeps a TCP connection open for a long
> time.

Yes, You're absolutely right at this point. I was thinking a lot since
Your message and I realized that maybe I have the same problems when
I'm using ssh. I've read somewhere that unlike other operating systems
linux has an adaptive timer for delaying ACKs, but I don't know how
it works or if it can go above 200ms or even it could be configured.

I know that this topic does not really belong here, but can someone
give me some hints about it?

> For instance, on the linux box, if port 12345 is open, you could
> install netcat (nc) and run:
>    $ nc -vlp 12345
> And on the other machines, you could try telnet'ing to port 12345
> ("telnet linux-box 12345" or "nc -v linux-box 12345") and see how long
> the connection stays up.
> --
> - Charles Lepple
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