How to determine whether client and server are on the same host

[Gregory Ewing]

Malte Forkel wrote:
> One special operation is not available in
> the protocol, but can be implemented by a direct file-based operation if
> the application is run on the server itself.

What would happen if you tried the file-based method when
it wasn't a local connection? Is there a danger of it
"succeeding" on the wrong machine and damaging something?

-- 
Greg