esp-idf/examples/protocols/mqtt/ssl_psk/README.md

Supported Targets	ESP32	ESP32-C2	ESP32-C3	ESP32-C6	ESP32-H2	ESP32-S2	ESP32-S3

ESP-MQTT SSL example with PSK verification

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

This example connects to a local broker configured to PSK authentication

How to use example

Hardware Required

This example can be executed on any ESP32 board, the only required interface is WiFi (or ethernet) to connect to a MQTT broker with preconfigured PSK verification method.

Mosquitto settings

In case of using mosquitto broker, here is how to enable PSK authentication in mosquitto.config,

psk_hint hint
psk_file path_to_your_psk_file
allow_anonymous true

Note: Last line enables anonymous mode, as this example does not use mqtt username and password.

PSK file then has to contain pairs of hints and keys, as shown below:

hint:BAD123

Important note: Keys are stored as text hexadecimal values in PSK file, while the example code stores key as plain binary as required by MQTT API. (See the example source for details: "BAD123" -> 0xBA, 0xD1, 0x23)

Configure the project

• Run 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.

Build and Flash

(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 (2160) example_connect: Ethernet Link Up
I (4650) example_connect: Connected to Ethernet
I (4650) example_connect: IPv4 address: 192.168.0.1
I (4650) MQTTS_EXAMPLE: [APP] Free memory: 244792 bytes
I (4660) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
D (4670) MQTT_CLIENT: MQTT client_id=ESP32_c6B4F8
D (4680) MQTT_CLIENT: Core selection disabled
I (4680) MQTTS_EXAMPLE: Other event id:7
D (4680) esp-tls: host:192.168.0.2: strlen 13
D (4700) esp-tls: ssl psk authentication
D (4700) esp-tls: handshake in progress...
D (4720) MQTT_CLIENT: Transport connected to mqtts://192.168.0.2:8883
I (4720) MQTT_CLIENT: Sending MQTT CONNECT message, type: 1, id: 0000
D (4720) MQTT_CLIENT: mqtt_message_receive: first byte: 0x20
D (4730) MQTT_CLIENT: mqtt_message_receive: read "remaining length" byte: 0x2
D (4730) MQTT_CLIENT: mqtt_message_receive: total message length: 4 (already read: 2)
D (4740) MQTT_CLIENT: mqtt_message_receive: read_len=2
D (4750) MQTT_CLIENT: mqtt_message_receive: transport_read():4 4
D (4750) MQTT_CLIENT: Connected
I (4760) MQTTS_EXAMPLE: MQTT_EVENT_CONNECTED
D (4760) MQTT_CLIENT: mqtt_enqueue id: 4837, type=8 successful
D (4770) OUTBOX: ENQUEUE msgid=4837, msg_type=8, len=18, size=18
D (4770) MQTT_CLIENT: Sent subscribe topic=/topic/qos0, id: 4837, type=8 successful
I (4780) MQTTS_EXAMPLE: sent subscribe successful, msg_id=4837
D (4790) MQTT_CLIENT: mqtt_enqueue id: 58982, type=8 successful
D (4790) OUTBOX: ENQUEUE msgid=58982, msg_type=8, len=18, size=36
D (4800) MQTT_CLIENT: Sent subscribe topic=/topic/qos1, id: 58982, type=8 successful
I (4810) MQTTS_EXAMPLE: sent subscribe successful, msg_id=58982