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MQTT Client Tutorial

Overview​

This tutorial covers the MQTT client example: connect to a public broker, subscribe, publish with QoS, then unsubscribe. The code uses mqtt_client_interface.h (init, connect, mqtt_client_yield, subscribe/publish/unsubscribe) on top of netmgr and Wi-Fi or wired networking.

Prerequisites​

Requirements​

  • Board config with MQTT client and network support for examples/protocols/mqtt_client.
  • Outbound access to the broker host and port (default sample uses broker.emqx.io:1883).
  • Broker credentials: the stock example uses EMQX demo username/password; replace for production or private brokers.

Steps​

  1. Open examples/protocols/mqtt_client.

  2. Edit src/examples_mqtt_client.c:

    • Wi-Fi SSID/password if using Wi-Fi.
    • mqtt_client_config_t: host, port, clientid, username, password, and callback hooks (on_connected, on_message, and so on).

  3. Build and flash from the example directory:

    cd examples/protocols/mqtt_client
    tos.py config choice
    tos.py build

  4. After link up, the sample calls mqtt_client_init, mqtt_client_connect, then mqtt_client_yield so the stack processes incoming packets. The connected callback subscribes; the subscribe callback publishes a test message; the publish-ack path unsubscribes.

Expected outcome: Serial log shows connect, subscribe, publish, and PUBACK, matching the callback order in the source.

Implementation notes​

  • You must call mqtt_client_yield (or an equivalent pump) regularly while connected, or the client will not process SUBACK/PUBLISH/PUBACK.
  • Topic names and payload encoding must match your cloud or broker contract.
  • This example is not the same as Tuya Cloud MQTT inside tuya_iot; it is a generic MQTT client for custom brokers.

References​