[Nut-upsuser] Upsmon and Winnut disconnect regularly

Charles Lepple clepple at gmail.com
Fri Dec 28 14:42:19 UTC 2007

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?

> 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

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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