It does. I wondered also, so I tried it out before I posted - actual
code below ...
on mouseup
open datagram socket to "10.0.0.33:4000" -- NB we don't care if
this succeeds or not
put shell("arp -a") into t
put t
end mouseup
-- Alex.
On 14/06/2013 23:09, Dar Scott wrote:
Cool idea. I wonder though. Will UDP actually trigger arp before the first
write? I'm not saying it won't, I'm just surprised. It would be cool it it
did.
Dar
On Jun 14, 2013, at 2:30 PM, Alex Tweedly wrote:
Sorry, I've been offline for a while, so this reply is coming kind of late, but
I don't think anything in the subsequent discussion invalidates it.
If you don't want to wait a second, you could do
(for address 10.0.0.232)
-- NB we don't care if this succeeds or not
open datagram socket to "10.0.0.232:4000"
-- if paranoid: wait for 10 ms
put shell("arp -a") into temp
filter temp with "*10.0.0.232*"
The open socket may or may not work - but it will resolve the IP address first, and hence
get an entry in the arp table. Then you can check variable 'temp' to verify the IP
address is there, and that it has an actual mac address corresponding to it (rather than
"incomplete").
NB "open datagram socket" will return without waiting for the socket to open; I think it
may do the addr resolution before returning, but you could be cautious / paranoid and do a
"wait 10 ms" before doing the arp check.
btw - corner case - if you have a router doing proxy arp replies (e.g. to
handle hosts that can't do default route), then this will falsely appear to
work - but AFAIK that is a very, very uncommon situation nowadays.
-- Alex.
On 13/06/2013 22:52, Dar Scott wrote:
On Jun 13, 2013, at 3:02 PM, Dr. Hawkins wrote:
Is there a *fast* way to see if another machine is currently on the
local network, by name (somemachine.local) or otherwise, from within
livecode?
There's always sending a message and waiting for it to hang, but I'd
like something that happens quickly.
On OS X:
You can use shell("arp -a") and look whether the IP address is included. The
list associates the underlying Ethernet address with the IP address. It will expire
after 20 minutes of non use. So, this really means this computer talked to that computer
in the last 20 minutes.
I think the best way has to involve a message. To keep it fast, use an IP
address rather than the host name. Use a method with a fast timeout.
You might be able to use shell(" ping -c 1 -t 1 10.9.8.7") but that would take
a second if the computer is not there.
If you have a service set up on that computer then you might be able to try
that.
On Windows:
Similar
Dar
---------------------------
Dar Scott
dba
Dar Scott Consulting
8637 Horacio Place NE
Albuquerque, NM 87111
Lab, home, office phone: +1 505 299 9497
For Skype and fax, please contact.
d...@swcp.com
Computer programming and tinkering,
usually in supporting those developing in
LiveCode--typically by making LiveCode
controls, libraries and externals, and
sometimes by writing associated
microcontroller firmware.
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