Hi all! Let me introduce luamqtt - https://github.com/xHasKx/luamqtt - the MQTT client library for Lua programming language . It's not based on any C module and written in pure Lua code from scratch and completely follows OASIS standards for the MQTT v5.0 and the MQTT v3.1.1 protocols. The only main dependency is a luasocket module to open a TCP connection. But there is a mechanism to implement your own functions to open a TCP connection and send/receive from it. It's used, for example, in the OpenResty to use its ngx.socket.tcp module instead of luasocket. This is a thread for discussion, feedback and feature requests of the luamqtt . Alternatively, the GitHub issues are welcomed.

Awesome work, I just found it and looking to give it a try on LogicMachine which don't have mosquitto package available.

DmitryG , Thanks! And don't hesitate to post here your LogicMachine integration experience!

Thanks, the main challenge with LM is that it does not support libraries, a library should be wrapped as a user script, which is basically a single file. I'm still trying to get my head around on how to "compile" this as i'm not Lua expert, yet.

DmitryG So you have to emulate module loading by require() function: https://www.lua.org/manual/5.3/manual.html#pdf-require You may try to wrap each module file into a function, returning the module table. And write your own require() function calling that module-emulating functions. Do you succeed with opening TCP connection to internet from the LM device?

Hi, it does have require(), however full module should be within a single file. Haven't had time to play around with that yet. I'm also waiting for forum account confirmation so I can get example of the other library wrapped from multiple source files. I will be making connections to local MQTT broker, but internet is also possible if network allows that.

kial hi, I finally managed to find some time to try it out - seems to work without major changes, the only step i had to make is to pre-build scripts into single file and update bit logic wrapper (LM have built-in support bit.XXX functions, but not language "<<" feature)

DmitryG , FYI, from v3.1.1 luamqtt will not require "bit" module if used with Lua 5.2, because this Lua version has a built-in module "bit32". If your LM runtime has Lua 5.2 or higher - it can simplify your deploy process

Hi, I am trying to implement your piece of code in my Sierrawireless RV50X. I do not understand how to use the "run_ioloop" fonction in order to publish message every minute. can you help please ? thanks in advance

aquaboxsalus , it depends on the Lua runtime available on your Sierrawireless RV50X. If it has some usual Lua interpreter - you may check out this test as an example: https://github.com/xHasKx/luamqtt/blob/master/tests/spec/ioloop.lua#L43 Here you have a function loop_func() which will be called again and again by the ioloop. So you can insert a code into it to calculate how much time has passed since the last sending (use os.time for example). When you calculated a 1-minute diff - send an MQTT message or whatever you need.

thanks. in the documentation i see that we can create an ioloop specifiying sleep argument ( sleep interval after each iteration (default 0)) correct ? is it not better ? how to use that ? thanks

luamqtt - MQTT client written in pure lua

jp_one

Hi folk, I'm trying to setup 2 clients running in parallel on the same device (they shall connect to different brokers. 1st to a local broker on the device, 2nd one to an off-board broker, e.g. flespi). I can add the 1st client to the loop. How to add the second client in a proper way? Shall I utilize e.g. the connack callback function? So if the 1st client is successfully connected, the second one shall start connecting. So something like this?
client1 = mqtt.client(client1_config)
mqtt.run_ioloop(client1)
on positive connack callback -->
client2 = mqtt.client(client2_config)
mqtt.run_ioloop(client2)

kial

jp_one Use this code to add another client to current ioloop when you need (for example, in the connack callback):
mqtt.get_ioloop():add(client2)

jp_one

kial sounds cool! Thx. I'll try out. Just another question: when mqtt.run_ioloop is started and under execution, I'll stay in the loop right? Or do i have the possibility to run and stop the loop on my own, whenever needed?

kial

jp_one mqtt.run_ioloop() is working as a blocking infinite loop which will exit only when all clients are removed from them (upon client disconnection usually).

HerrmannPaul

Dear Kial, is it possible to input PROXY settings into the connection?
I'm behind a corporate Firewall and with paho-mqtt (Python) I hat to adjust proxy settings for the connection to make mqtt running.
My working python solution is the following:

myClient = mqtt.Client(client_id="myID") myClient.username_pw_set(username = myUsrName,password = myPasswd) myClient.proxy_set(proxy_type = socks.HTTP, proxy_addr="127.0.0.1", proxy_port = 3128) connectionStatus = myClient.connect(host=myIP,port=myPORT, keepalive = 5)

Can you help me out doint this with luaMQTT?

kial

HerrmannPaul, the luamqtt lib does not support socks proxy, and brief googling does not help me to find a lua library that can do it transparently for the luasocket (TCP connections layer).
But anyway you can create a custom connector that will pass the TCP connection through your proxy.

And the alternative way for you is to install or create software that will listen for a plain TCP socket on the localhost and pass it through your HTTP proxy to the MQTT broker.

zt190

Hello,
I am currently working on a project involving Teltonika devices, specifically with smart meters. The objective of this project is to retrieve meter readings and transmit the data to the Azure portal. When I am trying to publish a message to Azure portal with the help of mqtt in Lua language but I am getting the "Connection Refused, not authorized" . I am referring this document https://github.com/xHasKx/luamqtt. I have used the same credentials for sending the data to Azure in python language and the python script is working. I am using the Lua 5.4 version and below is my lua script

local mqtt = require("mqtt")
local json = require("lunajson")

local luasec =  require("ssl")
print("using luasec runtime version: ", luasec._VERSION)
local path_to_root_cert = "<root directory>/src/cert/digicert.crt"
local device_id = "Teltonika02";
local sas_token = "SharedAccessSignature sr=<hostname>.azure-devices.net&sig=xeJT3F1XsYB5uIcbLjW3L9do4NXlUIOC1kBfNZ5zHuQ%3D&skn=iothubowner&se=2045963831";
local iot_hub_name = "<hostname>.azure-devices.net/<device id>/?api-version=2021-04-12";

local client = mqtt.client({
	  uri = "<hostname>.azure-devices.net",
    username = iot_hub_name,
    secure = {
        mode = "client",
        protocol = "tlsv1_2",
        cafile = path_to_root_cert,
        certificate = nil,
        key = nil
     },
    password = sas_token,
    version = mqtt.v50,
    clean = true
});
print(client,  ":  client")
local topic = "devices/" .. device_id .. "/messages/events/$.ct=application%2Fjson%3Bcharset%3Dutf-8"
local payload = [[{'id':123}]]

client:on{
    connect = function(connack)
        print("connack....", connack)
        if connack.rc ~= 0 then
            print("connection to broker failed:", connack:reason_string(), connack)
            return
        end
        print("Now go for subscribe")
        -- connection established, now subscribe to test topic and publish a message after
        assert(client:subscribe{ topic=topic, qos=1, callback=function()
            assert(client:publish{ topic = topic, payload = payload })
        end})
    end,
    message = function(msg)
        print(msg, ": messgae")
        assert(client:acknowledge(msg))

        -- receive one message and disconnect
        print("received message", msg)
        client:disconnect()
    end,
}

-- run ioloop for client
mqtt.run_ioloop(client)
-- Check if the MQTT client is connected
if client.connected then
   print("Connection is established")
else
   print("Connection is not established : ", client.connected)
end

shal

zt190 take a look at device policy. It should allow your client to connect to the hub with given client-id, subscribe and publish to specific topics. Enable all options if unsure.
Here is the article we touch Azure device policy a bit: https://flespi.com/kb/flespi-to-azure

jp_one

Hi guys, many thanks for the great module! I'm trying to utilize SSL/TLS in order to securely communicate with flespi broker. Is my understanding correct, that luamqtt is not supporting certificate based authentication?

So if token is regarded as not secure enough and luamqtt is used as MQTT client, the only way would to go would be via port 8883 or 443?

kial

jp_one I'm trying to utilize SSL/TLS in order to securely communicate with flespi broker. Is my understanding correct, that luamqtt is not supporting certificate based authentication?

If you mean SSL/TLS secure transport for MQTT protocol - it's fully supported if your Lua runtime has a luasec (or compatible) module. And you can specify any custom SSL parameters like certificate file in the secure={...} table parameter in mqtt client instance constructor (see secure parameter description there).

If you are talking about new MQTT 5.0 packet type AUTH - it's also supported in the luamqtt with client:auth() method. But this is a broker-specific authentication method, thus you cannot use it with flespi broker.

jp_one So if token is regarded as not secure enough and luamqtt is used as MQTT client

Sorry, I can't understand this part. Can you please rephrase it?

jp_one the only way would to go would be via port 8883 or 443?

I would say that you always should use port 8883 and SSL/TLS secure connection.
But port 443 is for websocket transport, which is not supported by luamqtt.

OleBier

I currently have the problem that both update functions (loop and sync) block the process until a message is received.
With the system I want to implement this library in I don't have the possibility to create a thread or have this run externally somehow. So the whole program will stop running until messages come in. I do however have the possibility to continually call a function. I thought I could use the run_sync methode as from the description, but that also waits for an incoming message.
So I would need something more in line of a function that checks if a message was reveiced, if not it just moves along. Is there a straightforward way of calling such a function?

kial

OleBier Can you please check how it's working on a pull request https://github.com/xhaskx/luamqtt/pull/31 ?

kial

OleBier Do you have a way to operate with TCP sockets in async (non-blocking) mode in your system? What is the system?

OleBier

Unfortunately the pull request didn't help with the problem.

OleBier

Honestly I have no idea. I haven't worked with networking that much to have a deeper understanding of it.
I'm working with the Defold game engine which incorporates luasocket as default. It is possible to use other libraries, but anything that's not pure Lua needs to be adapted to the engine for it to work properly, so I would like to avoid that.
Previously I used the MQTT client library from Paho, with which you manually had to call the handler in intervalls, which was perfect for my use case as the game engine does provide a function that gets periodically called. Recently we've updated our server and along with it switched to a newer version of Mosquitto, but I constantly get disconnected from it. So I was looking into using a newer MQTT library that also features MQTT version 5 and this one looked very promising.
I hoped that there possibly would be some kind of function I could call instead of using the two give one. But poking at the library myself a bit I guess I will needs to make certain adjustments to use it.

kial

OleBier Regarding your description I suppose you need function ioloop_mt:iteration() - https://github.com/xHasKx/luamqtt/blob/master/mqtt/ioloop.lua#L109

You can access it with

local ioloop = require("mqtt.ioloop")

print(ioloop.get().iteration) -- function: 0x612d866782c0

This function intended to be run in some outer loop, but I think your engine's handler will be suitable for that too.

OleBier

Thank you for creating the library and all the help you have given me. I managed to get it working with adding the following code to the init.lua. Which is basically just a slightly changed run_ioloop(...)

local loop = ioloop_get()
function mqtt.init_ioloop(...)
	for i = 1, select("#", ...) do
		local cl = select(i, ...)
		loop:add(cl)
		if type(cl) ~= "function" then
			cl:start_connecting()
		end
	end
end

function mqtt.iterate_ioloop()
	loop:iteration()
end

BochraDahmen

Hello,

I’m using CoppeliaSim for robot simulation and LuaMQTT to connect the robot to a local Mosquitto MQTT broker. The issue is that the MQTT connection is blocking the simulation, preventing the robot from moving based on MQTT payloads received in topics.

I’m trying to use async code to handle the MQTT connection without blocking the simulation, but it’s not working as expected. When the MQTT connection is established, the simulation gets blocked.

I’ve used coroutines in CoppeliaSim and LuaMQTT’s callback functions, but the MQTT connection still seems to block the simulation.

Has anyone managed to make this work asynchronously in CoppeliaSim? Any help would be appreciated!

PS: Just to be clear, the broker works, and both publish and subscribe functions work. However, when the MQTT connection is established, the simulation crashes.

The link to my Lua script:
https://www.blackbox.ai/share/eb9b70e1-466e-4b61-8713-c810981d41ae

Thank you in advance for your help!

kial

BochraDahmen , the call for mqtt.run_ioloop(client) is blocking your runtime. You need to run ioloop_mt:iteration() method of the default ioloop instance there instead. Default ioloop can be obtained with require("mqtt.ioloop").get() function

BochraDahmen

kial Thank you very much for your help! My code required a few adjustments related to the luamqtt library, such as using ioloop_mt:iteration(), as well as modifications specific to CoppeliaSim, like ensuring the coroutine is resumed at least once per simulation step.

For anyone who might find it useful, here is the working code, it connects CoppeliaSim to a local MQTT broker in a non-blocking way :

function sysCall_init()
    sim = require('sim')

    -- Initialize MQTT
    package.path = package.path .. ";C:/Program Files/CoppeliaRobotics/CoppeliaSimEdu/lua/mqtt/?.lua"
    print("Package path updated:", package.path)

    local mqtt = require("mqtt")
    local ioloop = require("mqtt.ioloop").get()  -- Get the default ioloop instance

    if not mqtt then
        error("Failed to load MQTT library. Check the path and ensure the library exists.")
    end

    -- Create MQTT client
    client = mqtt.client{
        uri = "127.0.0.1:1883", 
        id = "robot_client",
        clean = true
    }

    if not client then
        error("Failed to create MQTT client.")
    end

    print("Created MQTT client:", client)

    -- Set up the MQTT client on events
    client:on{
        connect = function(connack)
            if connack.rc ~= 0 then
                print("Connection to broker failed:", connack:reason_string(), connack)
                return
            end
            print("Connected to broker:", connack)  

            -- Subscribe to the topic after connection
            assert(client:subscribe{
                topic = "robot/commands",
                qos = 2,
                callback = function(suback)
                    print("Subscribed to topic:", suback)
                end
            })
        end,

        message = function(msg)
            assert(client:acknowledge(msg))  
            print("Received message:", msg.topic, msg.payload)
        end,

        error = function(err)
            print("MQTT client error:", err)
        end,

        close = function()
            print("MQTT connection closed")
        end
    }

    -- Attach client to the ioloop
    local success, err = pcall(function()
        ioloop:add(client)
    end)
    if not success then
        print("Failed to add client to ioloop:", err)
        return
    end
    print("Client added to ioloop")

    -- Create the coroutine for the MQTT loop
    mqttCoroutine = coroutine.create(function()
        while true do
            local success, err = pcall(function()
                ioloop:iteration(0.1)  -- Small timeout to prevent excessive CPU usage
            end)
            if not success then
                print("Error in ioloop iteration:", err)
            end
            coroutine.yield()  -- Yield control back to CoppeliaSim
        end
    end)
end

-- Resume the coroutine in the sensing function
function sysCall_sensing()
    if coroutine.status(mqttCoroutine) ~= 'dead' then
        local ok, errorMsg = coroutine.resume(mqttCoroutine)
        if errorMsg then
            error(debug.traceback(mqttCoroutine, errorMsg), 2)
        end
    end
end