162 lines
8.1 KiB
ReStructuredText
162 lines
8.1 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 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 tcp, default port 8883
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* :example:`protocols/mqtt/ssl_psk`: MQTT over tcp 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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URI
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^^^
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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.eclipse.org``: MQTT over TCP, default port 1883:
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- ``mqtt://mqtt.eclipse.org:1884`` MQTT over TCP, port 1884:
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- ``mqtt://username:password@mqtt.eclipse.org: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.eclipse.org``: MQTT over SSL, port 8883
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- ``mqtts://mqtt.eclipse.org:8884``: MQTT over SSL, port 8884
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- MQTT over Websocket samples:
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- ``ws://mqtt.eclipse.org:80/mqtt``
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- MQTT over Websocket Secure samples:
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- ``wss://mqtt.eclipse.org: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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.uri = "mqtt://mqtt.eclipse.org",
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// .user_context = (void *)your_context
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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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SSL
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^^^
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- Get certificate from server, example: ``mqtt.eclipse.org``
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``openssl s_client -showcerts -connect mqtt.eclipse.org: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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.uri = "mqtts://mqtt.eclipse.org:8883",
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.event_handle = mqtt_event_handler,
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.cert_pem = (const char *)mqtt_eclipse_org_pem_start,
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};
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If the certificate is not null-terminated then ``cert_len`` should also be set.
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Other SSL related configuration parameters are:
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* ``use_global_ca_store``: use the global certificate store to verify server certificate, see ``esp-tls.h`` for more information
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* ``client_cert_pem``: pointer to certificate data in PEM or DER format for SSL mutual authentication, default is NULL, not required if mutual authentication is not needed.
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* ``client_cert_len``: length of the buffer pointed to by client_cert_pem. May be 0 for null-terminated pem.
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* ``client_key_pem``: pointer to private key data in PEM or DER format for SSL mutual authentication, default is NULL, not required if mutual authentication is not needed.
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* ``client_key_len``: length of the buffer pointed to by client_key_pem. May be 0 for null-terminated pem.
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* ``psk_hint_key``: pointer to PSK struct defined in esp_tls.h to enable PSK authentication (as alternative to certificate verification). If not NULL and server/client certificates are NULL, PSK is enabled
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* ``alpn_protos``: NULL-terminated list of protocols to be used for ALPN.
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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``-struct.
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* ``lwt_topic``: pointer to the LWT message topic
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* ``lwt_msg``: pointer to the LWT message
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* ``lwt_msg_len``: length of the LWT message, required if ``lwt_msg`` is not null-terminated
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* ``lwt_qos``: quality of service for the LWT message
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* ``lwt_retain``: specifies the retain flag of the LWT message
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Other Configuration Parameters
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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* ``disable_clean_session``: determines the clean session flag for the connect message, defaults to a clean session
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* ``keepalive``: determines how many seconds the client will wait for a ping response before disconnecting, default is 120 seconds.
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* ``disable_auto_reconnect``: enable to stop the client from reconnecting to server after errors or disconnects
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* ``user_context``: custom context that will be passed to the event handler
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* ``task_prio``: MQTT task priority, defaults to 5
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* ``task_stack``: MQTT task stack size, defaults to 6144 bytes, setting this will override setting from menuconfig
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* ``buffer_size``: size of MQTT send/receive buffer, default is 1024 bytes
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* ``username``: pointer to the username used for connecting to the broker
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* ``password``: pointer to the password used for connecting to the broker
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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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* ``host``: MQTT broker domain (ipv4 as string), setting the uri will override this
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* ``port``: MQTT broker port, specifying the port in the uri will override this
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* ``transport``: sets the transport protocol, setting the uri will override this
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* ``refresh_connection_after_ms``: refresh connection after this value (in milliseconds)
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* ``event_handle``: handle for MQTT events as a callback in legacy mode
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* ``event_loop_handle``: handle for MQTT event loop library
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For more options on ``esp_mqtt_client_config_t``, please refer to API reference below
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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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