Re: [lwip-users] elegant way to detect network connection

[Sergio R. Caprile]

Hi Noam,
I was about to say you could sniff how windows 7+ does it; but I don't 
think they would do it in an elegant, not even standard, way... ;^)

I don't know if I get the whole picture, but I bet your problem is an 
"application ping". Do you actually need to know link is present or 
another device like yours or server or @ access or ?

Yes, ICMP Echo Requests might be discarded by the router, I think it is 
a bad idea on an internal network, but some admins think otherwise.
That is why I suggest "application ping", as long as your devices can 
see each other, you know you have a link. It is usually done on a 
separate UDP port, but some guys like to dedicate in-band commands to 
that purpose, like a keep-alive message. What I suggest is sort of a 
discovery protocol on UDP broadcasts, or a directed app ping if you know 
your neighbors addresses.

Toying with your DHCP server every half a second might pester some net 
admins and get you enemies for free... I wouldn't go that way, I think 
your application's problems have to be solved by your application. Just 
my 2 cents.

Regards!