Possible solution to determine if default network has changed (MacOS only for now)

[Bob Sneidar]

Hi all. 

MacOS only for now. 

I think I put together a way to tell if the default network has changed since the last time an internet connection took place. It's no good of course, just getting the IP address, as given an identical subnet, you have a 1 in 254 change of getting the same IP address on a different network. We want to be absolutely certain. 

Similarly, the gateway, subnet mask and DNS might also be identical. Finally, the only adapter we care about is the one that is being used as the default route to the internet or local resources. (there may be more than one active adapter, as in the Ethernet and Wireless adapters). 

The trick is to get the MAC address of the router, then store it and compare it each time you attempt to communicate. Here's what I came up with. Feel free to chide me if I am overthinking this:

on mouseUp
   put "route get default" into tShellCommand
   put shell(tShellCommand) into tDefaultAdapter
   put lineOffset("Interface: ", tDefaultAdapter) into tInterfaceLine
   
   if tInterfaceLine = 0 then 
      answer info "No default interface found!" as sheet
      exit mouseUp
   end if
   
   put word 2 of line tInterfaceLine of tDefaultAdapter into tDefaultInterface
   put "ipconfig getpacket " & tDefaultInterface into tShellCommand
   put shell(tShellCommand) into tInterfaceDetail
   put lineOffset("router (ip_mult): ", tInterfaceDetail) into tRouterLine
   put word 3 of line tRouterLine of tInterfaceDetail into tRouterAddress
   put char 2 to -2 of tRouterAddress into tRouterAddress
   put tRouterAddress
   put "arp " & tRouterAddress into tShellCommand
   put shell(tShellCommand) into tArpReply
   put word 4 of tArpReply into tDefaultMACAddress
end mouseUp

Bob S