Publish DHT22 to MQTT on an ESP8266 (wemos D1 mini)

wemos_dht.lua

-- DHT22 to MQTT Publisher
-- Andrew Elwell, 2016-06-08

client='ESP-'..node.chipid()
m = mqtt.Client(client, 60)
m:lwt("status/"..client, "offline", 0, 1)

m:connect("10.1.1.251", 1883, 0, 1, function(hohoho) 
      print("connected")
      hohoho:publish(string.format("status/%s", client, 0, 1))
    end,
    function (anothername, reason)
      print("failed reason", reason)
    end
    )

function readDHT()
-- Read Temp from DHT22 on pin 4
status, temp, humi, temp_dec, humi_dec = dht.read(4)
if status == dht.OK then
    payload = ('{ "temp": '..temp..', "humidity": '..humi..' }')
    print(payload)
    m:publish('sensors/'..client..'/json', payload,0,0)
elseif status == dht.ERROR_CHECKSUM then
    print( "DHT Checksum error." )
elseif status == dht.ERROR_TIMEOUT then
    print( "DHT timed out." )
end
end


tmr.alarm(0, 3000, tmr.ALARM_AUTO, function() readDHT(); end)