mqtt.lua

-- https://github.com/nodemcu/nodemcu-firmware/wiki/nodemcu_api_en
wifi.setmode(wifi.STATION)
wifi.sta.config("iotlab1","IoTInnoLab")

mqttOnline = false
mqttSubSuccess = false

-- timer vars
mainTimerId = 0 -- we have seven timers! 0..6
mainInterval = 1000 -- milliseconds
statusTimerID = 1
statusInterval = 10000
hackTimerID = 2
hackTimerInterval = 100
-- client ID, keepalive (seconds), user, password
m = mqtt.Client("ESP8266_dev", 30, "305f9533-6d4a-4c2d-886a-f7fbcb4a08f5", "qmtpIXtIgeQW")

m:lwt("/v1/305f9533-6d4a-4c2d-886a-f7fbcb4a08f5/data", cjson.encode({txt = "offline"}), 0, 0)

m:on("connect", function(con)
   print("connected")
   mqttOnline = true
   local msg = cjson.encode({{ meaning = 'string', value = 'hello world'}, {meaning = 'integer', value = tmr.now()} })
   m:publish("/v1/305f9533-6d4a-4c2d-886a-f7fbcb4a08f5/data", msg)
   -- hack to prevent stdio bomb calling subscribe in this callback
   tmr.alarm(hackTimerID, hackTimerInterval, 0, function()
      m:subscribe("/v1/305f9533-6d4a-4c2d-886a-f7fbcb4a08f5/data",0, function(con)
         print("subscribe success")
         mqttSubSuccess = true
      end)
   end)
end)

function updateMQTT()
   if wifi.sta.status() == 5 then
         print("calling m:connect()")
         m:connect("mqtt.relayr.io", 1883)
   end
end



m:on("offline", function(con)
   print("offline")
   mqttOnline = false
   mqttSubSuccess = false
end)