a *fast* check for whether another machine is on the local network?

[Dr. Hawkins]

On Thu, Jun 13, 2013 at 4:53 PM, Daryl Williams
<daryl at synergetic-data.com> wrote:
> If I am understanding correctly you might try using either the netstat or
> route commands to find your default gateway, and if there is none then save
> things to the local database.

doesn't give me the timeout issues again--if the laptop is opened in
the new location, won't the old router still be on the list, and need
to be checked?


> The problem with this approach will be determining the right syntax to use
> for the current platform your code is running on. Unfortunately the syntax
> is a bit different from windows to os x to linux, but they will all report
> on the routing tables, including the default router, at which point you just
> need to parse the command output (again different from platform to platform)
> an take the appropriate action. The output can be rather detailed and
> verbose, but should not too hard to parse.

This isn't too big of a problem--I already have OS based switches
lying around the code.  I guess I'll have to buy a windows machine for
the first time in my life to do some testing of that code on, though .
. .

After going through all of these, it sounds like the controlled
timeout is the way to go--when this stack comes to the front, it does
a check.  If it thinks it's not on the VPN already, it just continues
to use the local cache db--unless it sees "something"? new telling it
that the VPN is back, in which case it tries.  If it thinks it should
be on VPN, it pings for good measure with the 1s/50ms timeout.  Hmm,
this can be delayed until the first db write, too.   So the only time
the user gets hit for the whole second is when he actually changes
from VPN to no VPN (blocked, no internet, whatever).

Thank you to all.  I now know more things I never expected to learn :)


-- 
Dr. Richard E. Hawkins, Esq.
(702) 508-8462