esp-mqtt

MQTT component for esp-idf projects based on the lwmqtt library

This component bundles the lwmqtt client and adds a simple async API similar to other esp networking components.

Installation

You can install the component by adding it as a git submodule:

git submodule add https://github.com/256dpi/esp-mqtt.git components/esp-mqtt
git submodule update --init --recursive

The component will automatically enable the LWIP receive buffers.

PlatformIO

You need to set CONFIG_LWIP_SO_RCVBUF=y manually in sdkconfig.

Example

Examples can be found here: https://github.com/256dpi/esp-mqtt/examples.

API

Initialize the component once by passing the necessary callbacks:

void esp_mqtt_init(esp_mqtt_status_callback_t scb, esp_mqtt_message_callback_t mcb,
                   size_t buffer_size, int command_timeout);

Optionally, configure a Last Will and Testament (a topic to be published by the broker in the event of an ungraceful disconnection):

void esp_mqtt_lwt(const char *topic, const char *payload, int qos, bool retained);

When the WiFi connection has been established, start the process:

void esp_mqtt_start(const char *host, const char *port, const char *client_id,
                    const char *username, const char *password);

When the client has connected, interact with the broker:

bool esp_mqtt_subscribe(const char *topic, int qos);
bool esp_mqtt_unsubscribe(const char *topic);
bool esp_mqtt_publish(const char *topic, uint8_t *payload, size_t len, int qos, bool retained);

If the WiFi connection has been lost, stop the process:

void esp_mqtt_stop();

TLS connection

TLS connection option based on the mbedtls component esp-idf framework.

To enable tls connection:

• Choose Enable TLS connection in menu of configuration esp-mqtt component.
• MQTT background process task stack size must be 9216 or more in esp-mqtt component config.
• Get CA certificate from chain of certificates call openssl s_client -showcerts -connect broker.shiftr.io:8883 (change host and port of your secure mqtt broker server).
• Put it in file server_root_cert.pem in main directory of your project. See example.
• Add to your component.mk file of main directory of your project :

COMPONENT_EMBED_TXTFILES := server_root_cert.pem

• Call

bool esp_mqtt_tls(bool verify, const unsigned char * cacert, size_t cacert_len);

function to set verify option and CA certificate in tls structure before calling void esp_mqtt_start().