MQTTComponent is the base class for all components that interact with MQTT to expose certain functionality or data from actuators or sensors to clients. More...

#include <mqtt_component.h>

Inheritance diagram for esphome::mqtt::MQTTComponent:

Public Member Functions
	MQTTComponent ()
	Constructs a MQTTComponent.

void	call_setup () override
	Override setup_ so that we can call send_discovery() when needed.

void	call_loop () override

void	call_dump_config () override

virtual void	send_discovery (JsonObject root, SendDiscoveryConfig &config)=0
	Send discovery info the Home Assistant, override this.

virtual bool	send_initial_state ()=0

virtual bool	is_internal ()

void	set_qos (uint8_t qos)
	Set QOS for state messages.

uint8_t	get_qos () const

void	set_retain (bool retain)
	Set whether state message should be retained.

bool	get_retain () const

void	disable_discovery ()
	Disable discovery. Sets friendly name to "".

bool	is_discovery_enabled () const

void	set_subscribe_qos (uint8_t qos)
	Set the QOS for subscribe messages (used in discovery).

virtual const char *	component_type () const =0
	Override this method to return the component type (e.g. "light", "sensor", ...)

template<typename T >
void	set_custom_state_topic (T &&custom_state_topic)
	Set a custom state topic. Do not set for default behavior.

template<typename T >
void	set_custom_command_topic (T &&custom_command_topic)

void	set_command_retain (bool command_retain)
	Set whether command message should be retained.

float	get_setup_priority () const override
	MQTT_COMPONENT setup priority.

void	set_availability (std::string topic, std::string payload_available, std::string payload_not_available)
	Set the Home Assistant availability data.

void	disable_availability ()

void	schedule_resend_state ()
	Internal method for the MQTT client base to schedule a resend of the state on reconnect.

bool	publish (const std::string &topic, const std::string &payload)
	Send a MQTT message.

bool	publish (const std::string &topic, const char *payload, size_t payload_length)
	Send a MQTT message.

bool	publish_json (const std::string &topic, const json::json_build_t &f)
	Construct and send a JSON MQTT message.

void	subscribe (const std::string &topic, mqtt_callback_t callback, uint8_t qos=0)
	Subscribe to a MQTT topic.

void	subscribe_json (const std::string &topic, const mqtt_json_callback_t &callback, uint8_t qos=0)
	Subscribe to a MQTT topic and automatically parse JSON payload.

Public Member Functions inherited from esphome::Component
virtual void	setup ()
	Where the component's initialization should happen.

virtual void	loop ()
	This method will be called repeatedly.

virtual void	dump_config ()

float	get_actual_setup_priority () const

void	set_setup_priority (float priority)

virtual float	get_loop_priority () const
	priority of loop().

void	call ()

virtual void	on_shutdown ()

virtual void	on_safe_shutdown ()

virtual bool	teardown ()
	Called during teardown to allow component to gracefully finish operations.

virtual void	on_powerdown ()
	Called after teardown is complete to power down hardware.

uint8_t	get_component_state () const

void	reset_to_construction_state ()
	Reset this component back to the construction state to allow setup to run again.

bool	is_in_loop_state () const
	Check if this component has completed setup and is in the loop state.

bool	is_idle () const
	Check if this component is idle.

virtual void	mark_failed ()
	Mark this component as failed.

	ESPDEPRECATED ("Use mark_failed(LOG_STR(\"static string literal\")) instead. Do NOT use .c_str() from temporary " "strings. Will stop working in 2026.6.0", "2025.12.0") void mark_failed(const char *message)

void	mark_failed (const LogString *message)

void	disable_loop ()
	Disable this component's loop.

void	enable_loop ()
	Enable this component's loop.

void	enable_loop_soon_any_context ()
	Thread and ISR-safe version of enable_loop() that can be called from any context.

bool	is_failed () const

bool	is_ready () const

virtual bool	can_proceed ()

bool	status_has_warning () const

bool	status_has_error () const

void	status_set_warning (const char *message=nullptr)

void	status_set_warning (const LogString *message)

void	status_set_error ()

	ESPDEPRECATED ("Use status_set_error(LOG_STR(\"static string literal\")) instead. Do NOT use .c_str() from temporary " "strings. Will stop working in 2026.6.0", "2025.12.0") void status_set_error(const char *message)

void	status_set_error (const LogString *message)

void	status_clear_warning ()

void	status_clear_error ()

void	status_momentary_warning (const char *name, uint32_t length=5000)
	Set warning status flag and automatically clear it after a timeout.

void	status_momentary_error (const char *name, uint32_t length=5000)
	Set error status flag and automatically clear it after a timeout.

bool	has_overridden_loop () const

void	set_component_source (const LogString *source)
	Set where this component was loaded from for some debug messages.

const LogString *	get_component_log_str () const
	Get the integration where this component was declared as a LogString for logging.

bool	should_warn_of_blocking (uint32_t blocking_time)

Protected Member Functions
std::string	get_discovery_topic_ (const MQTTDiscoveryInfo &discovery_info) const
	Helper method to get the discovery topic for this component.

std::string	get_default_topic_for_ (const std::string &suffix) const
	Get this components state/command/... topic.

virtual const EntityBase *	get_entity () const =0
	Gets the Entity served by this MQTT component.

std::string	friendly_name_ () const
	Get the friendly name of this MQTT component.

StringRef	get_icon_ref_ () const
	Get the icon field of this component as StringRef.

bool	is_disabled_by_default_ () const
	Get whether the underlying Entity is disabled by default.

std::string	get_state_topic_ () const
	Get the MQTT topic that new states will be shared to.

std::string	get_command_topic_ () const
	Get the MQTT topic for listening to commands.

bool	is_connected_ () const

bool	send_discovery_ ()
	Internal method to start sending discovery info, this will call send_discovery().

StringRef	get_default_object_id_to_ (std::span< char, OBJECT_ID_MAX_LEN > buf) const
	Get the object ID for this MQTT component, writing to the provided buffer.

Protected Member Functions inherited from esphome::Component
void	set_component_state_ (uint8_t state)
	Helper to set component state (clears state bits and sets new state)

void	set_interval (uint32_t id, uint32_t interval, std::function< void()> &&f)
	Set an interval function with a numeric ID (zero heap allocation).

void	set_interval (uint32_t interval, std::function< void()> &&f)

bool	cancel_interval (uint32_t id)

void	set_retry (uint32_t id, uint32_t initial_wait_time, uint8_t max_attempts, std::function< RetryResult(uint8_t)> &&f, float backoff_increase_factor=1.0f)
	Set a retry function with a numeric ID (zero heap allocation).

void	set_retry (uint32_t initial_wait_time, uint8_t max_attempts, std::function< RetryResult(uint8_t)> &&f, float backoff_increase_factor=1.0f)

bool	cancel_retry (uint32_t id)

void	set_timeout (uint32_t id, uint32_t timeout, std::function< void()> &&f)
	Set a timeout function with a numeric ID (zero heap allocation).

void	set_timeout (uint32_t timeout, std::function< void()> &&f)

bool	cancel_timeout (uint32_t id)

void	defer (std::function< void()> &&f)
	Defer a callback to the next loop() call.

void	defer (uint32_t id, std::function< void()> &&f)
	Defer a callback with a numeric ID (zero heap allocation)

bool	cancel_defer (uint32_t id)

Protected Attributes
TemplatableValue< std::string >	custom_state_topic_ {}

TemplatableValue< std::string >	custom_command_topic_ {}

std::unique_ptr< Availability >	availability_

bool	command_retain_ {false}

bool	retain_ {true}

uint8_t	qos_ {0}

uint8_t	subscribe_qos_ {0}

bool	discovery_enabled_ {true}

bool	resend_state_ {false}

Protected Attributes inherited from esphome::Component
ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") void set_interval(const std voi	set_interval )(const char *name, uint32_t interval, std::function< void()> &&f)
	Set an interval function with a unique name.

ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") bool cancel_interval(const std boo	cancel_interval )(const char *name)
	Cancel an interval function.

ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") void set_retry(const std voi	set_retry )(const char *name, uint32_t initial_wait_time, uint8_t max_attempts, std::function< RetryResult(uint8_t)> &&f, float backoff_increase_factor=1.0f)
	Set an retry function with a unique name.

ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") bool cancel_retry(const std boo	cancel_retry )(const char *name)
	Cancel a retry function.

ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") void set_timeout(const std voi	set_timeout )(const char *name, uint32_t timeout, std::function< void()> &&f)
	Set a timeout function with a unique name.

ESPDEPRECATED("Use const char* or uint32_t overload instead. Removed in 2026.7.0", "2026.1.0") bool cancel_timeout(const std boo	cancel_timeout )(const char *name)
	Cancel a timeout function.

ESPDEPRECATED("Use const char* overload instead. Removed in 2026.7.0", "2026.1.0") void defer(const std voi	defer )(const char *name, std::function< void()> &&f)
	Defer a callback to the next loop() call.

ESPDEPRECATED("Use const char* overload instead. Removed in 2026.7.0", "2026.1.0") bool cancel_defer(const std boo	cancel_defer )(const char *name)
	Cancel a defer callback using the specified name, name must not be empty.

const LogString *	component_source_ {nullptr}

uint16_t	warn_if_blocking_over_ {WARN_IF_BLOCKING_OVER_MS}
	Warn if blocked for this many ms (max 65.5s)

uint8_t	component_state_ {0x00}
	State of this component - each bit has a purpose: Bits 0-2: Component state (0x00=CONSTRUCTION, 0x01=SETUP, 0x02=LOOP, 0x03=FAILED, 0x04=LOOP_DONE) Bit 3: STATUS_LED_WARNING Bit 4: STATUS_LED_ERROR Bits 5-7: Unused - reserved for future expansion.

volatile bool	pending_enable_loop_ {false}
	ISR-safe flag for enable_loop_soon_any_context.

Detailed Description

MQTTComponent is the base class for all components that interact with MQTT to expose certain functionality or data from actuators or sensors to clients.

Although this class should work with all MQTT solutions, it has been specifically designed for use with Home Assistant. For example, this class supports Home Assistant MQTT discovery out of the box.

In order to implement automatic Home Assistant discovery, all sub-classes should:

Implement send_discovery that creates a Home Assistant discovery payload.
Override component_type() to return the appropriate component type such as "light" or "sensor".
Subscribe to command topics using subscribe() or subscribe_json() during setup().

In order to best separate the front- and back-end of ESPHome, all sub-classes should only parse/send MQTT messages and interact with back-end components via callbacks to ensure a clean separation.

Definition at line 76 of file mqtt_component.h.

Constructor & Destructor Documentation

◆ MQTTComponent()

esphome::mqtt::MQTTComponent::MQTTComponent ( )

explicitdefault

Constructs a MQTTComponent.

Member Function Documentation

◆ call_dump_config()

void esphome::mqtt::MQTTComponent::call_dump_config ( )

overridevirtual

Reimplemented from esphome::Component.

Definition at line 331 of file mqtt_component.cpp.

◆ call_loop()

void esphome::mqtt::MQTTComponent::call_loop ( )

overridevirtual

Reimplemented from esphome::Component.

Definition at line 311 of file mqtt_component.cpp.

◆ call_setup()

void esphome::mqtt::MQTTComponent::call_setup ( )

overridevirtual

Override setup_ so that we can call send_discovery() when needed.

Reimplemented from esphome::Component.

Definition at line 290 of file mqtt_component.cpp.

◆ component_type()

virtual const char * esphome::mqtt::MQTTComponent::component_type ( ) const

pure virtual

Override this method to return the component type (e.g. "light", "sensor", ...)

◆ disable_availability()

void esphome::mqtt::MQTTComponent::disable_availability ( )

Definition at line 289 of file mqtt_component.cpp.

◆ disable_discovery()

void esphome::mqtt::MQTTComponent::disable_discovery ( )

Disable discovery. Sets friendly name to "".

Definition at line 279 of file mqtt_component.cpp.

◆ friendly_name_()

std::string esphome::mqtt::MQTTComponent::friendly_name_ ( ) const

protected

Get the friendly name of this MQTT component.

Definition at line 341 of file mqtt_component.cpp.

◆ get_command_topic_()

std::string esphome::mqtt::MQTTComponent::get_command_topic_ ( ) const

protected

Get the MQTT topic for listening to commands.

Definition at line 102 of file mqtt_component.cpp.

◆ get_default_object_id_to_()

StringRef esphome::mqtt::MQTTComponent::get_default_object_id_to_ ( std::span< char, OBJECT_ID_MAX_LEN > buf ) const

protected

Get the object ID for this MQTT component, writing to the provided buffer.

Definition at line 342 of file mqtt_component.cpp.

◆ get_default_topic_for_()

std::string esphome::mqtt::MQTTComponent::get_default_topic_for_ ( const std::string & suffix ) const

protected

Get this components state/command/... topic.

Parameters

suffix The suffix/key such as "state" or "command".

Returns: The full topic.

Definition at line 71 of file mqtt_component.cpp.

◆ get_discovery_topic_()

std::string esphome::mqtt::MQTTComponent::get_discovery_topic_ ( const MQTTDiscoveryInfo & discovery_info ) const

protected

Helper method to get the discovery topic for this component.

Definition at line 50 of file mqtt_component.cpp.

◆ get_entity()

virtual const EntityBase * esphome::mqtt::MQTTComponent::get_entity ( ) const

protectedpure virtual

Gets the Entity served by this MQTT component.

◆ get_icon_ref_()

StringRef esphome::mqtt::MQTTComponent::get_icon_ref_ ( ) const

protected

Get the icon field of this component as StringRef.

Definition at line 345 of file mqtt_component.cpp.

◆ get_qos()

uint8_t esphome::mqtt::MQTTComponent::get_qos ( ) const

Definition at line 260 of file mqtt_component.cpp.

◆ get_retain()

bool esphome::mqtt::MQTTComponent::get_retain ( ) const

Definition at line 262 of file mqtt_component.cpp.

◆ get_setup_priority()

float esphome::mqtt::MQTTComponent::get_setup_priority ( ) const

overridevirtual

MQTT_COMPONENT setup priority.

Reimplemented from esphome::Component.

Definition at line 278 of file mqtt_component.cpp.

◆ get_state_topic_()

std::string esphome::mqtt::MQTTComponent::get_state_topic_ ( ) const

protected

Get the MQTT topic that new states will be shared to.

Definition at line 96 of file mqtt_component.cpp.

◆ is_connected_()

bool esphome::mqtt::MQTTComponent::is_connected_ ( ) const

protected

Definition at line 338 of file mqtt_component.cpp.

◆ is_disabled_by_default_()

bool esphome::mqtt::MQTTComponent::is_disabled_by_default_ ( ) const

protected

Get whether the underlying Entity is disabled by default.

Definition at line 346 of file mqtt_component.cpp.

◆ is_discovery_enabled()

bool esphome::mqtt::MQTTComponent::is_discovery_enabled ( ) const

Definition at line 264 of file mqtt_component.cpp.

◆ is_internal()

bool esphome::mqtt::MQTTComponent::is_internal ( )

virtual

Definition at line 347 of file mqtt_component.cpp.

◆ publish() [1/2]

bool esphome::mqtt::MQTTComponent::publish	(	const std::string &	topic,
		const char *	payload,
		size_t	payload_length )

Send a MQTT message.

Parameters

topic	The topic.
payload	The payload buffer.
payload_length	The length of the payload.

Definition at line 112 of file mqtt_component.cpp.

◆ publish() [2/2]

bool esphome::mqtt::MQTTComponent::publish	(	const std::string &	topic,
		const std::string &	payload )

Send a MQTT message.

Parameters

topic	The topic.
payload	The payload.

Definition at line 108 of file mqtt_component.cpp.

◆ publish_json()

bool esphome::mqtt::MQTTComponent::publish_json	(	const std::string &	topic,
		const json::json_build_t &	f )

Construct and send a JSON MQTT message.

Parameters

topic	The topic.
f	The Json Message builder.

Definition at line 118 of file mqtt_component.cpp.

◆ schedule_resend_state()

void esphome::mqtt::MQTTComponent::schedule_resend_state ( )

Internal method for the MQTT client base to schedule a resend of the state on reconnect.

Definition at line 337 of file mqtt_component.cpp.

◆ send_discovery()

virtual void esphome::mqtt::MQTTComponent::send_discovery	(	JsonObject	root,
		SendDiscoveryConfig &	config )

pure virtual

Send discovery info the Home Assistant, override this.

◆ send_discovery_()

bool esphome::mqtt::MQTTComponent::send_discovery_ ( )

protected

Internal method to start sending discovery info, this will call send_discovery().

Definition at line 124 of file mqtt_component.cpp.

◆ send_initial_state()

virtual bool esphome::mqtt::MQTTComponent::send_initial_state ( )

pure virtual

◆ set_availability()

void esphome::mqtt::MQTTComponent::set_availability	(	std::string	topic,
		std::string	payload_available,
		std::string	payload_not_available )

Set the Home Assistant availability data.

See See Home Assistant for more info.

Definition at line 282 of file mqtt_component.cpp.

◆ set_command_retain()

void esphome::mqtt::MQTTComponent::set_command_retain ( bool command_retain )

Set whether command message should be retained.

Definition at line 280 of file mqtt_component.cpp.

◆ set_custom_command_topic()

template<typename T >

void esphome::mqtt::MQTTComponent::set_custom_command_topic ( T && custom_command_topic )

inline

Definition at line 117 of file mqtt_component.h.

◆ set_custom_state_topic()

template<typename T >

void esphome::mqtt::MQTTComponent::set_custom_state_topic ( T && custom_state_topic )

inline

Set a custom state topic. Do not set for default behavior.

Definition at line 114 of file mqtt_component.h.

◆ set_qos()

void esphome::mqtt::MQTTComponent::set_qos ( uint8_t qos )

Set QOS for state messages.

Definition at line 44 of file mqtt_component.cpp.

◆ set_retain()

void esphome::mqtt::MQTTComponent::set_retain ( bool retain )

Set whether state message should be retained.

Definition at line 48 of file mqtt_component.cpp.

◆ set_subscribe_qos()

void esphome::mqtt::MQTTComponent::set_subscribe_qos ( uint8_t qos )

Set the QOS for subscribe messages (used in discovery).

Definition at line 46 of file mqtt_component.cpp.

◆ subscribe()

void esphome::mqtt::MQTTComponent::subscribe	(	const std::string &	topic,
		mqtt_callback_t	callback,
		uint8_t	qos = 0 )

Subscribe to a MQTT topic.

Parameters

topic	The topic. Wildcards are currently not supported.
callback	The callback that will be called when a message with matching topic is received.
qos	The MQTT quality of service. Defaults to 0.

Definition at line 268 of file mqtt_component.cpp.

◆ subscribe_json()

void esphome::mqtt::MQTTComponent::subscribe_json	(	const std::string &	topic,
		const mqtt_json_callback_t &	callback,
		uint8_t	qos = 0 )

Subscribe to a MQTT topic and automatically parse JSON payload.

If an invalid JSON payload is received, the callback will not be called.

Parameters

topic	The topic. Wildcards are currently not supported.
callback	The callback with a parsed JsonObject that will be called when a message with matching topic is received.
qos	The MQTT quality of service. Defaults to 0.

Definition at line 272 of file mqtt_component.cpp.

Field Documentation

◆ availability_

std::unique_ptr<Availability> esphome::mqtt::MQTTComponent::availability_

protected

Definition at line 221 of file mqtt_component.h.

◆ command_retain_

bool esphome::mqtt::MQTTComponent::command_retain_ {false}

protected

Definition at line 223 of file mqtt_component.h.

◆ custom_command_topic_

TemplatableValue<std::string> esphome::mqtt::MQTTComponent::custom_command_topic_ {}

protected

Definition at line 219 of file mqtt_component.h.

◆ custom_state_topic_

TemplatableValue<std::string> esphome::mqtt::MQTTComponent::custom_state_topic_ {}

protected

Definition at line 218 of file mqtt_component.h.

◆ discovery_enabled_

bool esphome::mqtt::MQTTComponent::discovery_enabled_ {true}

protected

Definition at line 227 of file mqtt_component.h.

◆ qos_

uint8_t esphome::mqtt::MQTTComponent::qos_ {0}

protected

Definition at line 225 of file mqtt_component.h.

◆ resend_state_

bool esphome::mqtt::MQTTComponent::resend_state_ {false}

protected

Definition at line 228 of file mqtt_component.h.

◆ retain_

bool esphome::mqtt::MQTTComponent::retain_ {true}

protected

Definition at line 224 of file mqtt_component.h.

◆ subscribe_qos_

uint8_t esphome::mqtt::MQTTComponent::subscribe_qos_ {0}

protected

Definition at line 226 of file mqtt_component.h.

The documentation for this class was generated from the following files:

esphome/components/mqtt/mqtt_component.h
esphome/components/mqtt/mqtt_component.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ MQTTComponent()

Member Function Documentation

◆ call_dump_config()

◆ call_loop()

◆ call_setup()

◆ component_type()

◆ disable_availability()

◆ disable_discovery()

◆ friendly_name_()

◆ get_command_topic_()

◆ get_default_object_id_to_()

◆ get_default_topic_for_()

◆ get_discovery_topic_()

◆ get_entity()

◆ get_icon_ref_()

◆ get_qos()

◆ get_retain()

◆ get_setup_priority()

◆ get_state_topic_()

◆ is_connected_()

◆ is_disabled_by_default_()

◆ is_discovery_enabled()

◆ is_internal()

◆ publish() [1/2]

◆ publish() [2/2]

◆ publish_json()

◆ schedule_resend_state()

◆ send_discovery()

◆ send_discovery_()

◆ send_initial_state()

◆ set_availability()

◆ set_command_retain()

◆ set_custom_command_topic()

◆ set_custom_state_topic()

◆ set_qos()

◆ set_retain()

◆ set_subscribe_qos()

◆ subscribe()

◆ subscribe_json()

Field Documentation

◆ availability_

◆ command_retain_

◆ custom_command_topic_

◆ custom_state_topic_

◆ discovery_enabled_

◆ qos_

◆ resend_state_

◆ retain_

◆ subscribe_qos_