OVMS3-idf/docs/en/api-reference/protocols/mqtt.rst

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ESP-MQTT
========
Overview
--------
ESP-MQTT is an implementation of MQTT protocol client (MQTT is a lightweight publish/subscribe messaging protocol).
Features
--------
* supports MQTT over TCP, SSL with mbedtls, MQTT over Websocket, MQTT over Websocket Secure.
* Easy to setup with URI
* Multiple instances (Multiple clients in one application)
* Support subscribing, publishing, authentication, will messages, keep alive pings and all 3 QoS levels (it should be a fully functional client).
Application Example
-------------------
* :example:`protocols/mqtt/tcp`: MQTT over tcp, default port 1883
* :example:`protocols/mqtt/ssl`: MQTT over tcp, default port 8883
* :example:`protocols/mqtt/ws`: MQTT over Websocket, default port 80
* :example:`protocols/mqtt/wss`: MQTT over Websocket Secure, default port 443
Configuration
-------------
URI
^^^
- Curently support ``mqtt``, ``mqtts``, ``ws``, ``wss`` schemes
- MQTT over TCP samples:
- ``mqtt://mqtt.eclipse.org``: MQTT over TCP, default port 1883:
- ``mqtt://mqtt.eclipse.org:1884`` MQTT over TCP, port 1884:
- ``mqtt://username:password@mqtt.eclipse.org:1884`` MQTT over TCP,
port 1884, with username and password
- MQTT over SSL samples:
- ``mqtts://mqtt.eclipse.org``: MQTT over SSL, port 8883
- ``mqtts://mqtt.eclipse.org:8884``: MQTT over SSL, port 8884
- MQTT over Websocket samples:
- ``ws://mqtt.eclipse.org:80/mqtt``
- MQTT over Websocket Secure samples:
- ``wss://mqtt.eclipse.org:443/mqtt``
- Minimal configurations:
.. code:: c
const esp_mqtt_client_config_t mqtt_cfg = {
.uri = "mqtt://mqtt.eclipse.org",
// .user_context = (void *)your_context
};
esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);
esp_mqtt_client_start(client);
- Note: By default mqtt client uses event loop library to post related mqtt events (connected, subsribed, published, etc.)
- If there are any options related to the URI in
``esp_mqtt_client_config_t``, the option defined by the URI will be
overridden. Sample:
.. code:: c
const esp_mqtt_client_config_t mqtt_cfg = {
.uri = "mqtt://mqtt.eclipse.org:1234",
.port = 4567,
};
//MQTT client will connect to mqtt.eclipse.org using port 4567
SSL
^^^
- Get certificate from server, example: ``mqtt.eclipse.org``
``openssl s_client -showcerts -connect mqtt.eclipse.org:8883 </dev/null 2>/dev/null|openssl x509 -outform PEM >mqtt_eclipse_org.pem``
- Check the sample application: ``examples/mqtt_ssl``
- Configuration:
.. code:: cpp
const esp_mqtt_client_config_t mqtt_cfg = {
.uri = "mqtts://mqtt.eclipse.org:8883",
.event_handle = mqtt_event_handler,
.cert_pem = (const char *)mqtt_eclipse_org_pem_start,
};
For more options on ``esp_mqtt_client_config_t``, please refer to API reference below
Change settings in Project Configuration Menu
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
::
idf.py menuconfig
-> Component config -> ESP-MQTT Configuration
- :ref:`CONFIG_MQTT_PROTOCOL_311`: Enables 3.1.1 version of MQTT protocol
- :ref:`CONFIG_MQTT_TRANSPORT_SSL`, :ref:`CONFIG_MQTT_TRANSPORT_WEBSOCKET`: Enables specific MQTT transport layer, such as SSL, WEBSOCKET, WEBSOCKET_SECURE
- :ref:`CONFIG_MQTT_CUSTOM_OUTBOX`: Disables default implementation of mqtt_outbox, so a specific implementaion can be supplied
API Reference
-------------
.. include:: /_build/inc/mqtt_client.inc