Infrastructure – WiFi & MQTT

Files
file	WiFiMqttClient.cpp
	Implementation of the WifiMqttClient helper class.

Classes
class	WifiMqttClient
	Combined WiFi and MQTT client abstraction. More...

Functions
	WifiMqttClient::WifiMqttClient ()
	Default constructor.
void	WifiMqttClient::begin (const char *wifiSsid, const char *wifiPass, const char *mqttHost, uint16_t mqttPort, const char *mqttUser, const char *mqttPass, const char *deviceId, const char *site)
	Initializes WiFi and MQTT configuration.
void	WifiMqttClient::loop ()
	Main service loop.
bool	WifiMqttClient::connected ()
	Checks whether the MQTT client is currently connected.
bool	WifiMqttClient::publishJson (const char *topicSuffix, const JsonDocument &data)
	Publishes a JSON document to an MQTT topic.
void	WifiMqttClient::setCallback (MQTT_CALLBACK_SIGNATURE)
	Sets the MQTT message callback.
bool	WifiMqttClient::subscribe (const char *topic)
	Subscribes to a topic.
bool	WifiMqttClient::unsubscribe (const char *topic)
	Unsubscribes from a topic.
String	WifiMqttClient::makeTopic (const char *suffix) const
	Constructs a fully qualified MQTT topic.

Detailed Description

This header defines the WifiMqttClient class, which encapsulates:

• WiFi connection management
• MQTT connection and reconnection logic
• Topic namespace handling (site / device scoping)
• JSON-based MQTT publish helpers

The class is designed to simplify MQTT usage in distributed embedded systems by providing a consistent base topic structure and robust connection handling.

Function Documentation

begin()

void WifiMqttClient::begin	(	const char *	wifiSsid,
		const char *	wifiPass,
		const char *	mqttHost,
		uint16_t	mqttPort,
		const char *	mqttUser,
		const char *	mqttPass,
		const char *	deviceId,
		const char *	site )

Initializes WiFi and MQTT configuration.

Stores credentials and connection parameters, initializes internal clients, and prepares base topic paths.

Parameters

wifiSsid	WiFi network SSID.
wifiPass	WiFi network password.
mqttHost	MQTT broker hostname or IP.
mqttPort	MQTT broker port.
mqttUser	MQTT username.
mqttPass	MQTT password.
deviceId	Unique device identifier (e.g. "door1").
site	Site or location identifier (e.g. "site1").

Stores provided credentials, prepares base topic structure, configures WiFi and MQTT clients, and performs initial connections.

Parameters

wifiSsid	WiFi network SSID.
wifiPass	WiFi network password.
mqttHost	MQTT broker hostname.
mqttPort	MQTT broker port.
mqttUser	MQTT username.
mqttPass	MQTT password.
deviceId	Device identifier used in topic hierarchy.
site	Site identifier used in topic hierarchy.

Definition at line 43 of file WiFiMqttClient.cpp.

connected()

bool WifiMqttClient::connected

(

)

Checks whether the MQTT client is currently connected.

Checks whether the MQTT client is connected.

Returns

true if MQTT connection is active, false otherwise.

true if connected, false otherwise.

Definition at line 108 of file WiFiMqttClient.cpp.

loop()

void WifiMqttClient::loop

(

)

Main service loop.

Must be called frequently from the Arduino loop(). Handles:

• WiFi reconnection
• MQTT reconnection
• MQTT client loop processing

Ensures WiFi and MQTT connections remain active and processes incoming MQTT messages.

Definition at line 87 of file WiFiMqttClient.cpp.

makeTopic()

String WifiMqttClient::makeTopic

(

const char *

suffix

)

const

Constructs a fully qualified MQTT topic.

Combines the base topic with a suffix: <user>/<site>/<deviceId>/<suffix>

Parameters

suffix

Topic suffix (e.g. "access/request").

Returns

Constructed topic as an Arduino String.

Appends a suffix to the base topic: <user>/<site>/<deviceId>/<suffix>

Parameters

suffix

Topic suffix.

Returns

Constructed topic as an Arduino String.

Definition at line 197 of file WiFiMqttClient.cpp.

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publishJson()

bool WifiMqttClient::publishJson	(	const char *	topicSuffix,
		const JsonDocument &	data )

Publishes a JSON document to an MQTT topic.

Automatically prefixes the topic with the base topic (<user>/<site>/<deviceId>/).

Parameters

topicSuffix	Topic suffix appended to the base topic.
data	JSON document to serialize and publish.

Returns

true if publish succeeded, false otherwise.

Wraps the provided JSON data in a standard envelope containing device metadata and a timestamp.

Parameters

topicSuffix	Topic suffix appended to the base topic.
data	JSON document containing application payload.

Returns

true if publish succeeded, false otherwise.

Definition at line 211 of file WiFiMqttClient.cpp.

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setCallback()

void WifiMqttClient::setCallback

(

MQTT_CALLBACK_SIGNATURE

)

Sets the MQTT message callback.

The callback is invoked when subscribed messages are received.

Parameters

MQTT_CALLBACK_SIGNATURE	Function pointer matching PubSubClient callback signature.
MQTT_CALLBACK_SIGNATURE	Callback function pointer.

Definition at line 244 of file WiFiMqttClient.cpp.

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subscribe()

bool WifiMqttClient::subscribe

(

const char *

topic

)

Subscribes to a topic.

Subscribes to an MQTT topic.

The provided topic should already be fully constructed (use makeTopic() if needed).

Parameters

topic

Full MQTT topic string.

Returns

true if subscription succeeded, false otherwise.

Parameters

topic

Full MQTT topic string.

Returns

true if subscription succeeded, false otherwise.

Definition at line 254 of file WiFiMqttClient.cpp.

unsubscribe()

bool WifiMqttClient::unsubscribe

(

const char *

topic

)

Unsubscribes from a topic.

Unsubscribes from an MQTT topic.

Parameters

topic

Full MQTT topic string.

Returns

true if unsubscribe succeeded, false otherwise.

Definition at line 265 of file WiFiMqttClient.cpp.

WifiMqttClient()

WifiMqttClient::WifiMqttClient

(

)

Default constructor.

Initializes internal state but does not establish any network connections.

Initializes the PubSubClient instance with the internal WiFiClient.

Definition at line 25 of file WiFiMqttClient.cpp.