Configuration

The MQTT Simulator configuration consists of 3 main sections: Broker, Topics, and Data.

Quick Navigation:
Broker settings • Topics settings • Data settings

You can also check a full settings file example at: settings.json.

Broker settings

The Broker settings section is located at the root level of the JSON configuration file and defines the fundamental MQTT connection 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. Version of the MQTT protocol to use for this client. Can be either 3 (MQTTv31), 4 (MQTTv311) or 5 (MQTTv5)
TLS_CA_PATH	string	None	Sets the paho.mqtt.client.tls_set ca_certs param. String path to the Certificate Authority certificate file
TLS_CERT_PATH	string	None	Sets the paho.mqtt.client.tls_set certfile param. String path to the PEM encoded client certificate file
TLS_KEY_PATH	string	None	Sets the paho.mqtt.client.tls_set keyfile param. String path to the PEM encoded client private keys file
AUTH_USERNAME	string	None	Sets the paho.mqtt.client.username_pw_set username param. Username to authenticate with
AUTH_PASSWORD	string	None	Sets the paho.mqtt.client.username_pw_set password param. Password to authenticate with
CLEAN_SESSION	bool	True	Sets the paho.mqtt.client clean_session param. Boolean that determines the client type. This property is ignored if PROTOCOL_VERSION is 5.
RETAIN	bool	False	Sets the paho.mqtt.client.publish retain param. If set to true, the message will be set as the “last known good”/retained message for the topic
QOS	number	2	Sets the paho.mqtt.client.publish qos param. Quality of service level to use
TIME_INTERVAL	number	10	Time interval in seconds between submissions towards the topic
TOPICS	array\	None	Specification of topics and how they will be published

Topics settings

The TOPICS key is a list. Each topic entry is an object containing parameters that define how topics will be structured and published:

{
    "TYPE": "multiple",
    "PREFIX": "place",
    "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\	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
PAYLOAD_ROOT	object	The root set of params to include on all messages	optional
DATA	array\	Specification of the data that will form the JSON to be sent in the topic	yes

Data settings

The key DATA inside TOPICS is a list. Each data entry is an object containing parameters that define individual data properties and how values are simulated:

{
    "NAME": "temperature",
    "TYPE": "float",
    "INITIAL_VALUE": 35,
    "MIN_VALUE": 20,
    "MAX_VALUE": 55,
    "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_values"	yes
INITIAL_VALUE	same that is returned according to TYPE	Initial value that the property will assume when the simulation starts. If not specified: random for "int", "float" or "bool", and determined by other parameters for "math_expression" or "raw_values"	optional
RETAIN_PROBABILITY	number	Number between 0 and 1 for the probability of the value being retained and sent again	optional, default is 0
RESET_PROBABILITY	number	Number between 0 and 1 for the probability of the value being reset to INITIAL_VALUE	optional, default is 0
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"
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_values"
INDEX_END	number	The index to end publishing from the VALUES array	optional, default is len(values) - 1. Only valid if TYPE is "raw_values"
RESTART_ON_END	bool	When true and the index of the VALUES array reaches INDEX_END, the next index will be INDEX_START. Otherwise, the param will become inactive and won’t be sent after reaching INDEX_END	optional, default is false. Only valid if TYPE is "raw_values"
VALUES	array\	The values to be published in array order	if TYPE is "raw_values"
VALUE_DEFAULT	object	The default value params used or overwritten by params in VALUES	optional, default is {}. Only valid if TYPE is "raw_values" and VALUES is an array\

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