Automatic Ethernet connection checking and informing in case of troubles ?

[Joep]

You can check some network futures yourself with the script below and do with it whatever you like. Run it as an init scrit and send an email with this information for example.
Have fun with it 

require('json')
require('socket.http')

ip = io.readproc('if-json')
ip = json.decode(ip)
log("IP address: " ..ip.eth0.inetaddr)

socket.http.timeout = 5
data = socket.http.request('http://ip-api.com/json')
if data then
  data = json.decode(data)
  log("WAN IP: "..data.query)
  log("City: "..data.city)
  log("Region: "..data.region)
  log("Country: "..data.countryCode)
  log("Latitude: "..data.lat)
  log("Longitude: "..data.lon)
else
  log("There is possible no internet connection")
end

log("DNS name: " ..socket.dns.gethostname())

io.input("/sys/class/net/eth0/carrier")
carrier = io.read("*line")
if carrier == "1" then
  log("Connected to the network")
else
  log("No connection to the network")
end

io.input("/sys/class/net/eth0/operstate")
state = io.read("*line")
if state == "up" then
  log("The network connection is active")
else
  log("The network connection is inactive")
end