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182 lines
8.5 KiB
ReStructuredText
182 lines
8.5 KiB
ReStructuredText
ESP-MQTT
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========
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Overview
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--------
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ESP-MQTT is an implementation of [MQTT](mqtt.org) protocol client (MQTT is a lightweight publish/subscribe messaging protocol).
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Features
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--------
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* Supports MQTT over TCP, SSL with mbedtls, MQTT over Websocket, MQTT over Websocket Secure.
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* Easy to setup with URI
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* Multiple instances (Multiple clients in one application)
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* Support subscribing, publishing, authentication, last will messages, keep alive pings and all 3 QoS levels (it should be a fully functional client).
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Application Example
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-------------------
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* :example:`protocols/mqtt/tcp`: MQTT over tcp, default port 1883
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* :example:`protocols/mqtt/ssl`: MQTT over tls, default port 8883
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* :example:`protocols/mqtt/ssl_ds`: MQTT over tls using digital signature peripheral for authentication, default port 8883.
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* :example:`protocols/mqtt/ssl_mutual_auth`: MQTT over tls using certificates for authentication, default port 8883
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* :example:`protocols/mqtt/ssl_psk`: MQTT over tls using pre-shared keys for authentication, default port 8883.
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* :example:`protocols/mqtt/ws`: MQTT over Websocket, default port 80
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* :example:`protocols/mqtt/wss`: MQTT over Websocket Secure, default port 443
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Configuration
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-------------
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The configuration is made by setting fields in ``esp_mqtt_client_config_t`` struct. The configuration struct has the following sub structs to configure different aspects of the client operation.
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* :cpp:member:`broker<esp_mqtt_client_config::broker>` - Allow to set address and security verification.
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* :cpp:member:`credentials<esp_mqtt_client_config::credentials>` - Client credentials for authentication.
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* :cpp:member:`session<esp_mqtt_client_config::session>` - Configuration for MQTT session aspects.
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* :cpp:member:`network<esp_mqtt_client_config::network>` - Networking related configuration.
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* :cpp:member:`task<esp_mqtt_client_config::task>` - Allow to configure FreeRTOS task.
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* :cpp:member:`buffer<esp_mqtt_client_config::buffer>` - Buffer size for input and output.
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In the following session the most common aspects are detailed.
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Broker
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^^^^^^^^^^^
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===========
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Address
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===========
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Broker address can be set by usage of ``broker.address`` struct. The configuration can be made by usage of ``uri`` field
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or the combination of ``hostname``, ``transport`` and ``port``. Optionally, `path` could be set, this field is useful in
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websocket connections.
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The ``uri`` field is used in the following format ``scheme://hostname:port/path``.
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- Curently support ``mqtt``, ``mqtts``, ``ws``, ``wss`` schemes
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- MQTT over TCP samples:
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- ``mqtt://mqtt.eclipseprojects.io``: MQTT over TCP, default port 1883:
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- ``mqtt://mqtt.eclipseprojects.io:1884`` MQTT over TCP, port 1884:
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- ``mqtt://username:password@mqtt.eclipseprojects.io:1884`` MQTT over TCP,
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port 1884, with username and password
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- MQTT over SSL samples:
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- ``mqtts://mqtt.eclipseprojects.io``: MQTT over SSL, port 8883
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- ``mqtts://mqtt.eclipseprojects.io:8884``: MQTT over SSL, port 8884
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- MQTT over Websocket samples:
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- ``ws://mqtt.eclipseprojects.io:80/mqtt``
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- MQTT over Websocket Secure samples:
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- ``wss://mqtt.eclipseprojects.io:443/mqtt``
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- Minimal configurations:
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.. code:: c
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const esp_mqtt_client_config_t mqtt_cfg = {
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.broker.address.uri = "mqtt://mqtt.eclipseprojects.io",
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};
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esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
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esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);
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esp_mqtt_client_start(client);
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- Note: By default mqtt client uses event loop library to post related mqtt events (connected, subscribed, published, etc.)
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============
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Verification
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============
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For secure connections TLS is used, and to guarantee Broker's identity the ``broker.verification`` struct must be set.
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The broker certificate may be set in PEM or DER format. To select DER the equivalent ``_len`` field must be set,
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otherwise a NULL terminated string in PEM format should be provided to ``certificate`` field.
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- Get certificate from server, example: ``mqtt.eclipseprojects.io``
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``openssl s_client -showcerts -connect mqtt.eclipseprojects.io:8883 </dev/null 2>/dev/null|openssl x509 -outform PEM >mqtt_eclipse_org.pem``
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- Check the sample application: ``examples/mqtt_ssl``
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- Configuration:
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.. code:: c
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const esp_mqtt_client_config_t mqtt_cfg = {
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.broker = {
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.address.uri = "mqtts://mqtt.eclipseprojects.io:8883",
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.verification.certificate = (const char *)mqtt_eclipse_org_pem_start,
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},
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};
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To details on other fields check the Reference API and :ref:`esp_tls_server_verification`.
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Client Credentials
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^^^^^^^^^^^^^^^^^^
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All client related credentials are under the ``credentials`` field.
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* ``username``: pointer to the username used for connecting to the broker, can also be set by URI.
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* ``client_id``: pointer to the client id, defaults to ``ESP32_%CHIPID%`` where %CHIPID% are the last 3 bytes of MAC address in hex format
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==============
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Authentication
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==============
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It's possible to set authentication parameters through the ``authentication`` field. The client supports the following authentication methods:
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* Using a password by setting ``authentication.password``.
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* Muthual authentication with TLS by setting ``authentication.certificate`` and ``authentication.key``, both can be provided in PEM or DER format.
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* Using secure element available in ESP32-WROOM-32SE, setting ``authentication.use_secure_element``.
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* Using Digital Signature Peripheral available in some Espressif devices, setting ``authentication.ds_data``.
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Session
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^^^^^^^^^^^
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For MQTT session related configurations ``section`` fields should be used.
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=======================
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Last Will and Testament
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=======================
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MQTT allows for a last will and testament (LWT) message to notify other clients when a client ungracefully disconnects. This is configured by the following fields
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in the ``esp_mqtt_client_config_t.session.last_will``-struct.
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* ``topic``: pointer to the LWT message topic
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* ``msg``: pointer to the LWT message
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* ``msg_len``: length of the LWT message, required if ``msg`` is not null-terminated
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* ``qos``: quality of service for the LWT message
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* ``retain``: specifies the retain flag of the LWT message
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Change settings in Project Configuration Menu
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The settings for MQTT can be found using ``idf.py menuconfig``, under Component config -> ESP-MQTT Configuration
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The following settings are available:
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- :ref:`CONFIG_MQTT_PROTOCOL_311`: Enables 3.1.1 version of MQTT protocol
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- :ref:`CONFIG_MQTT_TRANSPORT_SSL`, :ref:`CONFIG_MQTT_TRANSPORT_WEBSOCKET`: Enables specific MQTT transport layer, such as SSL, WEBSOCKET, WEBSOCKET_SECURE
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- :ref:`CONFIG_MQTT_CUSTOM_OUTBOX`: Disables default implementation of mqtt_outbox, so a specific implementaion can be supplied
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Events
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------
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The following events may be posted by the MQTT client:
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* ``MQTT_EVENT_BEFORE_CONNECT``: The client is initialized and about to start connecting to the broker.
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* ``MQTT_EVENT_CONNECTED``: The client has successfully established a connection to the broker. The client is now ready to send and receive data.
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* ``MQTT_EVENT_DISCONNECTED``: The client has aborted the connection due to being unable to read or write data, e.g. because the server is unavailable.
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* ``MQTT_EVENT_SUBSCRIBED``: The broker has acknowledged the client's subscribe request. The event data will contain the message ID of the subscribe message.
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* ``MQTT_EVENT_UNSUBSCRIBED``: The broker has acknowledged the client's unsubscribe request. The event data will contain the message ID of the unsubscribe message.
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* ``MQTT_EVENT_PUBLISHED``: The broker has acknowledged the client's publish message. This will only be posted for Quality of Service level 1 and 2, as level 0 does not use acknowledgements. The event data will contain the message ID of the publish message.
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* ``MQTT_EVENT_DATA``: The client has received a publish message. The event data contains: message ID, name of the topic it was published to, received data and its length. For data that exceeds the internal buffer multiple `MQTT_EVENT_DATA` will be posted and `current_data_offset` and `total_data_len` from event data updated to keep track of the fragmented message.
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* ``MQTT_EVENT_ERROR``: The client has encountered an error. `esp_mqtt_error_type_t` from `error_handle` in the event data can be used to further determine the type of the error. The type of error will determine which parts of the `error_handle` struct is filled.
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API Reference
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-------------
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.. include-build-file:: inc/mqtt_client.inc
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