Re: Connection question

On 2/09/2010 11:59 PM, Bayless Kirtley wrote:
> Thanks a lot Craig. The register is connecting through localhost so it's
> not that. I
> guess I'm not surprised about the Windows thing. I suppose we'll just
> have to
> live with it then.

I wouldn't be too sure yet.

Did you run the test where you reboot the POS system with the ethernet
unplugged? Does it still connect to the database OK?

I didn't think XP broke TCP/IP connections to *localhost* when an
ethernet interface went up or down, unless the connection was to a local
IP associated with that interface. If you're connected to 127.0.0.1 from
127.0.0.1 it shouldn't, AFAIK, matter if you lose your wifi/ethernet.

Come to think of it, you might want to check to make sure the local
Ethernet interface is set to use DHCP. If it's using a static IP,
Windows might permit that IP to be used to talk to the local host even
when there's no link on the interface. So - to be sure, you can disable
the Ethernet interface in the network control panel before your reboot
for testing.

Anyway, if you really can't make it work properly, there's a simple if
mildly clumsy workaround. You can prevent XP from realizing it's lost
its connection to the router by placing another device between the XP
machine(s) and the router, like a plain old cheap switch. That way
Ethernet link on the XP machines is never lost when you reboot the
router - only between the router and the switch, where the XP machines
can't tell. When the router goes down they lose their DHCP server, but
that doesn't matter if it comes up again before they try to renew their
DHCP leases, and for local-to-local traffic that's about all they'll be
relying on the router for. You could even avoid that by setting static
IP addresses.

--
Craig Ringer

Tech-related writing at http://soapyfrogs.blogspot.com/