bug#21727: Tramp hangs in Windows

[Michael Albinus <michael.albinus@gmx.de>]

Arni Magnusson <arnima@hafro.is> writes:

Hi Arni,

> Thank you for looking into this, Michael.
>
> You are right, this problem is machine-specific. I tried loading Tramp
> in Emacs 24.5 on my colleague's Windows 7 laptop (next door office)
> and it works.

Good to know.

> Alas, I'm not able to determine what is improper about my DNS
> settings, if that is the case. All settings seem to be set to default
> (obtain DNS server addresss automatically) and no network-related
> applications show any symptoms of improper DNS settings. They all work
> smoothly (Putty, wget, Firefox, Skype, etc.), both on the wireless at
> home and the ethernet at work. As a simple test, I tried unplugging
> the ethernet cable to go offline, but Tramp still hangs.

No, that's not the point. Tramp wants to check some ssh arguments, and
tries to contact an *inalid* host name on purpose. If DNS is configured
properly, there will be an immediate reaction that this is an invalid FQDN.

> The Linux commands in bug thread 20015 do not apply to diagnose the
> problem in native Windows. Can you suggest some test I can run to
> analyze what is causing the problem?

Well, I don't run Windows personally, so my advice might be wrong. But
you could open a cmd.exe window, and try

# ssh -o ControlPath=%C host.does.not.exist

Likely, it will hang for you.

An alternative could be to install Emacs 25.0.50. This works pretty
stable, and Tramp has changed its test to be used w/o DNS. You find
weekly snapshots at <https://sourceforge.net/projects/emacs-bin/>.

> Thanks,
>
> Arni

Best regards, Michael.