scripitng

[mariosp]

hello i made this script i receive to error logs this ( User script:13: attempt to call field 'listen' (a nil value) stack tracebackan anyone help me 

local smtp_server = 'logicmachine email'
local smtp_port = 587
local smtp_user = 'admin'
local smtp_pass = 'admin'
local recipient = 'mariospoulorinis@gmail.com'
local subject = 'Ειδοποίηση: Ενεργοποίηση αισθητήρα βροχής'
local message = 'Ομπρέλα να πάρεις'




event.listen(rain_sensor_ga, function(event)
  if value == true then 
    log
  ' email(smtp_server, smtp_port, smtp_user, smtp_pass, recipient, subject, message)'
   
  end
end)