Easy-to-configure MQTT simulator written in Python 3 to simulate the sending of JSON objects from sensors or devices to a broker.

Features • Getting Started • Configuration • Authors

• Small and easy-to-configure simulator for publishing data to a broker
• Configuration from a single JSON file
• Connection on pre-defined fixed topics
• Connection on multiple topics that have a variable id or items at the end
• Random variation of data generated according to configuration parameters

• Python 3 (with pip)

To install all dependencies with a virtual environment:

python3 -m venv venv
source venv/bin/activate
pip3 install -r requirements.txt

The default simulator settings can be changed in the config/settings.json file.

python3 mqtt-simulator/main.py

Runs the simulator according to the settings file.
The terminal will show the simulator event log.

Optionally, you can pass a flag with the path to settings file:

python3 mqtt-simulator/main.py -f <path/settings.json>

Additionally, you can run via Docker with the included Dockerfile.

Build the image:

docker build -t mqtt-simulator .

Run the container:

docker run mqtt-simulator -f <path/settings.json>

• The config/settings.json file has the following main configuration parameters:

  {
      "BROKER_URL": "mqtt.eclipse.org",
      "BROKER_PORT": 1883,
      "TOPICS": [
          ...
      ]
  }

  Key	Type	Default	Description
  BROKER_URL	string	localhost	The broker URL where the data will be published
  BROKER_PORT	number	1883	The port used by the broker
  PROTOCOL_VERSION	number	4	Sets the paho.mqtt.client protocol param which is the version of the MQTT protocol to use for this client. Can be either 3 (MQTTv31), 4 (MQTTv311) or 5 (MQTTv5)
  CLEAN_SESSION	bool	True	Sets the paho.mqtt.client clean_session param which is a boolean that determines the client type. This property is ignored if PROTOCOL_VERSION is 5.
  RETAIN	bool	False	Sets the paho.mqtt.publish retain param which sets the “last known good”/retained message for the topic
  QOS	number	2	Sets the paho.mqtt.publish qos param which is the quality of service level to use
  TIME_INTERVAL	number	10	Time interval in seconds between submissions towards the topic
  TOPICS	array<Objects>	None	Specification of topics and how they will be published

• The key TOPICS has a array of objects where each one has the format:

  {
      "TYPE": "multiple",
      "PREFIX": "temperature",
      "RANGE_START": 1,
      "RANGE_END": 2,
      "TIME_INTERVAL": 25,
      "DATA": [
          ...
      ]
  }

  Key	Type	Description	Required
  TYPE	string	It can be "single", "multiple" or "list"	yes
  PREFIX	string	Prefix of the topic URL, depending on the TYPE it can be concatenated to /<id> or /<item>	yes
  LIST	array<any>	When the TYPE is "list" the topic prefix will be concatenated with /<item> for each item in the array	if TYPE is "list"
  RANGE_START	number	When the TYPE is "multiple" the topic prefix will be concatenated with /<id> where RANGE_START will be the first number	if TYPE is "multiple"
  RANGE_END	number	When the TYPE is "multiple" the topic prefix will be concatenated with /<id> where RANGE_END will be the last number	if TYPE is "multiple"
  CLEAN_SESSION	bool	Overwrites the broker level config value and applies only to this Topic	no
  RETAIN	bool	Overwrites the broker level config value and applies only to this Topic	no
  QOS	number	Overwrites the broker level config value and applies only to this Topic	no
  TIME_INTERVAL	number	Overwrites the broker level config value and applies only to this Topic	no
  DATA	array<Objects>	Specification of the data that will form the JSON to be sent in the topic	yes

• The key DATA inside TOPICS has a array of objects where each one has the format:

  {
      "NAME": "temperature",
      "TYPE": "float",
      "INITIAL_VALUE": 35,
      "MIN_VALUE": 30,
      "MAX_VALUE": 40,
      "MAX_STEP": 0.2,
      "RETAIN_PROBABILITY": 0.5,
      "RESET_PROBABILITY": 0.1,
      "INCREASE_PROBABILITY": 0.7,
      "RESTART_ON_BOUNDARIES": true
  }

  Key	Type	Description	Required
  NAME	string	JSON property name to be sent	yes
  TYPE	string	It can be "int", "float", "bool", "math_expression", or "raw_value"	yes
  INITIAL_VALUE	number or bool (same as defined in TYPE)	Initial value that the property will assume when the simulation starts (random otherwise)	optional. Only valid if TYPE is different from "math_expression"
  MIN_VALUE	number	Minimum value that the property can assume	if TYPE is "int" or "float"
  MAX_VALUE	number	Maximum value that the property can assume	if TYPE is "int" or "float"
  MAX_STEP	number	Maximum change that can be applied to the property from a published data to the next	if TYPE is "int" or "float"
  RETAIN_PROBABILITY	number	Number between 0 and 1 for the probability of the value being retained and sent again	yes
  RESET_PROBABILITY	number	Number between 0 and 1 for the probability of the value being reset to INITIAL_VALUE	optional, default is 0. Only valid if TYPE is different from "math_expression"
  INCREASE_PROBABILITY	number	Number between 0 and 1 for the probability of the next value being greater than the previous one	optional, default is 0.5 (same probability to increase or decrease). Only valid if TYPE is "int" or "float"
  RESTART_ON_BOUNDARIES	bool	When true and the value reaches MAX_VALUE or MIN_VALUE the next value will be the INITIAL_VALUE	optional, default is false. Only valid if TYPE is "int" or "float"
  MATH_EXPRESSION	string	Math expression written in a Pythonic way Also accept functions from Math modules	if TYPE is "math_expression"
  INTERVAL_START	number	Minimum value that the MATH_EXPRESSION's variable x can assume	if TYPE is "math_expression"
  INTERVAL_END	number	Maximum value that the MATH_EXPRESSION's variable x can assume	if TYPE is "math_expression"
  MIN_DELTA	number	Minimum value that can be added to the MATH_EXPRESSION's variable x from a published data to the next	if TYPE is "math_expression"
  MAX_DELTA	number	Maximum value that can be added to the MATH_EXPRESSION's variable x from a published data to the next	if TYPE is "math_expression"
  INDEX_START	number	The index to start publishing from the VALUES array	optional, default is 0. Only valid if TYPE is "raw_value"
  INDEX_END	number	The index to end publishing from the VALUES array	optional, default is len(values) - 1. Only valid if TYPE is "raw_value"
  RESTART_ON_END	bool	When true and the index of the VALUES array reaches INDEX_END the next value will be the INDEX_START. Otherwise the client will disconnect when reaching the end	optional, default is false. Only valid if TYPE is "raw_value"
  VALUES	array<any>	The values to be published in array order	if TYPE is "raw_value"

  NOTE: Access math_expression.md file for more explanations and a example of TYPE: "math_expression".