uart module vs spi module ?

[crapthings]

Which should i use ?

mqttClient:on("message", function(conn, topic, data)
uart.write(0, data)
end)

i've got this crashed by using uart.write

PANIC: unprotected error in call to Lua API (mqtt.lua:16: bad argument #2 to 'write' (

[nodemcu]

I think maybe the data is nil, can you check it with

--uart.write(0, data)
if data then uart.write(0, data)

[crapthings]

thanks will give a try ~