Modbus diconnection (read failed)

[Gadjoken]

Hello,
I would like to send an email when there is a modbus disconnection for 30 minutes, the fact that there is random disconnection any time makes that the sending of the mail can occur while the modbus still works . I wish I could have a return of this defect but if it is continual during 30 minutes ... is it possible?
B. R.


Current Script : 

require('luamodbus')
mb = luamodbus.tcp()

-- IP: xxx.xxx.xxx.xxx, port: 502
mb:open('xxx.xxx.xxx.xxx', 502)
mb:connect()

conectMB = mb:readregisters(5)

mb:close()

-- CREATION DES SUJET ET MESSAGE POUR MAIL

subject = 'subject'
message = 'message'

subject1 = 'subject1'
message1 = 'message1'

-- ENVOI DU MAIL SI ALARME VRAI

defaut_conectMB = storage.get('defaut_conectMB', false)

if conectMB == nil then
  if not defaut_conectMB then
    mail('@', subject, message)
    storage.set('defaut_conectMB', true)
  end
else
  if defaut_conectMB then
    mail('@', subject1, message1)
    storage.set('defaut_conectMB', false)
  end
end