Berry-UdpBroker

A lightweight messaging solution for Tasmota devices.

Mission

This application implements a message broker functionality using Multicast-UDP.

Motivation

There are scenarios in which one or more of the following conditions apply:

• There should be as few technical dependencies as possible
• No MQTT-Broker is available
• MQTT messages are used for monitoring only, not for prodcutive mechanisms
• MQTT-Broker is located in the Cloud and not useful for productive local usage

How it works

• the application opens a Multicast-UDP-Port on IP="224.3.0.1" and PORT=12233.
• now it is able to receive all corresponding broadcast messages
• if there exists a 'subscriber' the message is forwarded
• the controller can send a broadcast message using Berry or Tasmota-Commands
• the sensor-message can also be send according to the teleperiod interval

Available Commands

Command	Example	Comment
udppub <topic> <payload>	udppub SM.simple 22.23	publish value '22.23' with topic 'SM.simple'
udpsub <topic>	udpsub SM.simple	subscribe for topic 'SM.simple'
udpunsub <topic>	udpunsub SM.simple	unsubscribe topic 'SM.simple'

Remarks

As a convention: The rule-trigger must begin with 'udpBroker#...'

You can subscribe the same topic for using 'Commands' by 'udpsub' and using 'Berry' by 'udpBroker.subscribe(<topic>).

Both subscriptions exist independently of each other. This also applies to unsubscribing to a topic.

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A simple 'rule' example

Controller-A publishes a value via udpBroker with topic 'SM.simple'.
Controller-B ist interested on that value and wants to store it in the variable 'var1'.

Controller-B: prepare a rule

The topic of the message is 'SM.simple'.

To distinguish it from other namespaces the prefix 'udpBroker' is always required within a rule definition.

rule1 
  ON udpBroker#SM.simple do var1 %value% ENDON 	
      
rule1 1

Controller-B: subscribe the the topic of interst

udpsub SM.simple 

Controller-A: publish the value

udppub SM.simple  22.23

Check the result

Check the output of the Console.

..MQT: stat/tasmota_testing/RESULT = {"Var1":"22.23"}

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An enhanced 'rule' example

Controller-A publishes a json-payload via udpBroker with topic 'SM.enhanced'.

{"Power":1000,"Voltage":220}

Controller-B ist interested on Property 'Voltage' and wants to store it in the variable 'var1'.

Controller-B: prepare a rule

Accessing elements of the json-payload is compliant with standard Tasmota practices.

rule1 
  ON udpBroker#SM.enhanced#Voltage do var1 %value% ENDON 

rule1 1

Controller-B: subscribe the the topic of interst

udpsub SM.enhanced

Controller-A: publish the value

udppub SM.enhanced  {"Power:1000,"Voltage":220} 

Check the result

Check the output of the Console.

..MQT: stat/tasmota_testing/RESULT = {"Var1":"220"}

Forward the complete SENSOR message

It is possible to publish the complete standard SENSOR message.

udpBroker.publishSensorMsg(true)

The publishing device shows following properties

Topic             : tasmota_testing
Sensor            : ADC Light
Sensor telegram    : ... MQT: tele/tasmota_testing/SENSOR = {"Time":"2024-01-14T12:25:35","ANALOG":{"Illuminance1":0}}

To capture the value of the “ANALOG” sensor on another device running udpBroker, you need to do the following in the console:

udpsub tele/tasmota_testing/SENSOR
rule1 ON udpBroker#tele/tasmota_testing/SENSOR#ANALOG#Illuminance1 do var1 %value% ENDON

How to install

Upload following files to the Controller

• udpBroker.tapp
• udpBroker01.be (is executed before components are created)
• udpBroker02.be (is after components are created)

After restart of the controller and you should see following picture of the file-system.

How to deal with Berry

Take a look to file udpBroker02.be.

Under the hood

The class UdpBroker is designed as a Tasmota-driver.

    tasmota.add_driver(self) 

Start/Stop of the broker

UdpBroker is started/stopped synchronized with Wifi-connection.

    tasmota.add_rule("Wifi#Connected", / -> self.start()) 
    tasmota.add_rule("Wifi#Disconnected", / -> self.stop()) 

High Load

Note that each broadcast message is processed by the controller. Too many messages can overwhelm the controller.

Enable Logging

The berry-variable 'udpBroker' is global.

Use following statement in the Berry-Console to obtain more log-information.

    udpBroker.infoEnable=true

No wildcard support for subscribing

Wildcard mechanisms like MQTT are omitted in favor of simplicity.

Insecure transmission with UDP

If you need a value once per minute, you should transfer it every 10 seconds.