MQTT Client Library Encyclopedia - Paho Lua
Written by Kévin KIN-FOO
Category: MQTT MQTT Client Library
Published: August 24, 2015
Paho Lua Client library implements client-side subset of the MQTT protocol specification 3.1. An advantage of using Lua is that only a text editor is required for rapid development of simple MQTT client applications on many platforms. Cross compilation issues are avoided.
Initially part of Aiko Platform, this library is now part of Eclipse Paho project.
As I am writing easiest way to install Paho Lua Client is from sources using LuaRocks.
You are all set.
Note: tested on Lua 5.1.
This section shows the API usage how to connect with the library to a MQTT broker.
First step is creating MQTT client, here test.mosquitto.org is used as broker host. As port is not specified, 1183 is used by default. Then you can simply call client:connect() with a client identifier of your choice.
Connect with Username / Password
Authentication is just one additional line.
Calling client:auth() before client:connect() enables to set username and password.
Once you are connected it is as simple as:
It publishes a
fancy message on
You can subscribe on several topics by providing them to
client:subscribe() in a table.
Once something arrives on topic, callback defined at connection is called.
You no longer want to get message from a topic? Put it in a table and give it to
Full Example Application
What we are doing here is publishing random strings on topic/sample forever until being told to “stop”.
First we connect to broker.mqttdashboard.com on default port 1883. At connection, we define a callback to handle received messages.
Then we subscribe to topic/sample topic.
Now we publish a string on topic we just subscribed to,
client:handler() checks for received messages. When there is one,
callback(topic, message) is called to deal with it. We repeat this relentlessly.
Once this message is string “stop”, we stop looping, unsubscribe from topic/sample.
To clean all this, we disconnect from server and destroy our client to free allocated memory.
You can also find this example code at https://github.com/KINFOO/org.eclipse.paho.lua.sample