ESP-MQTT sample application

(See the README.md file in the upper level 'examples' directory for more information about examples.)

This example connects to the broker URI selected using idf.py menuconfig (using mqtt tcp transport) and as a demonstration subscribes/unsubscribes and send a message on certain topic. (Please note that the public broker is maintained by the community so may not be always available, for details please see this disclaimer)

Note: If the URI equals FROM_STDIN then the broker address is read from stdin upon application startup (used for testing)

It uses ESP-MQTT library which implements mqtt client to connect to mqtt broker.

How to use example

Hardware Required

This example can be executed on any ESP32 board, the only required interface is WiFi and connection to internet.

Configure the project

• Open the project configuration menu (idf.py menuconfig)
• Configure Wi-Fi or Ethernet under "Example Connection Configuration" menu. See "Establishing Wi-Fi or Ethernet Connection" section in examples/protocols/README.md for more details.
• When using Make build system, set Default serial port under Serial flasher config.

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

idf.py -p PORT flash monitor

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

I (3714) event: sta ip: 192.168.0.139, mask: 255.255.255.0, gw: 192.168.0.2
I (3714) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (3964) MQTT_CLIENT: Sending MQTT CONNECT message, type: 1, id: 0000
I (4164) MQTT_EXAMPLE: MQTT_EVENT_CONNECTED
I (4174) MQTT_EXAMPLE: sent publish successful, msg_id=41464
I (4174) MQTT_EXAMPLE: sent subscribe successful, msg_id=17886
I (4174) MQTT_EXAMPLE: sent subscribe successful, msg_id=42970
I (4184) MQTT_EXAMPLE: sent unsubscribe successful, msg_id=50241
I (4314) MQTT_EXAMPLE: MQTT_EVENT_PUBLISHED, msg_id=41464
I (4484) MQTT_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=17886
I (4484) MQTT_EXAMPLE: sent publish successful, msg_id=0
I (4684) MQTT_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=42970
I (4684) MQTT_EXAMPLE: sent publish successful, msg_id=0
I (4884) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (4884) MQTT_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data
I (5194) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (5194) MQTT_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data