MQTT

Kconfig: CONFIG_MODULE_MQTT — GClasses: C_PROT_MQTT, C_PROT_MQTT2, C_MQTT_BROKER

Full MQTT protocol implementation (v3.1.1 + v5.0) with a persistent message broker backed by TreeDB.

C_PROT_MQTT / C_PROT_MQTT2¶

MQTT protocol with publish, subscribe, QoS levels, and event-driven message handling. C_PROT_MQTT2 is the current implementation (and works as both the broker’s per-connection protocol and a standalone client — see mqtt_tui). C_PROT_MQTT is the legacy version kept for backward compatibility.

Trace levels (C_PROT_MQTT2): traffic (packets, no payload), traffic-payload, show-decode (decoded packet structure), messages2.

Secrets: user_passw, jwt and auth_data (the MQTT 5 AUTH data of the connection, C_PROT_MQTT too) are SDF_SECRET: view-attrs, view-gobj and list-persistent-attrs show them as ******** (an empty one stays empty). Up to 7.25.20 auth_data showed in clear.

A frame the protocol refuses is dumped in the log, at every trace level (“MQTT malformed packet: ”, length-capped). Of a CONNECT only the head is dumped, the protocol name, level, flags and keep alive, and of an AUTH only its reason code: the properties and the payload carry the credentials. Up to 7.25.20 the whole CONNECT was dumped, password included.

"msg": "MQTT malformed packet: CMD_CONNECT (credentials not dumped)",
"data": {"0000": "00 04 4D 51 54 54 05 C2 00 3C     ..MQTT...<"}

ycommand -c 'command-yuno id=<id> service=__yuno__ command=view-attrs gobj=<C_PROT_MQTT2 full name> attribute=auth_data'
# {"C_PROT_MQTT2^<name>": "********"}

C_MQTT_BROKER¶

Full MQTT message broker — subscriber management, message routing, session handling, and persistent storage using TreeDB on timeranger2.

Trace levels: messages, messages2.

Driven by the mqtt_broker yuno — see that page for the protocol/persistence/configuration details.

C API¶

The helpers the three gclasses share have pages of their own:

• MQTT utilities (mqtt_util.h) -- names of the protocol’s codes, validation of topics and UTF-8, the record of a message.

• tr2q (tr2q_mqtt.h) -- the persistent queues of a session, on timeranger2.

Registration¶

Register the gclasses a yuno uses once, in register_yuno_and_more(), before creating them; a second call of the same one fails with “GClass ALREADY created”. Each one returns 0, or -1 (logged) when the gclass cannot be created.

int register_c_prot_mqtt(void);
int register_c_prot_mqtt2(void);
int register_c_mqtt_broker(void);

The mqtt_broker yuno registers the protocol and the broker:

static int register_yuno_and_more(void)
{
    register_c_prot_mqtt2();
    register_c_mqtt_broker();
    return 0;
}

register_c_prot_mqtt() — C_PROT_MQTT¶

The deprecated protocol, kept until the remaining gates migrate to C_PROT_MQTT2.

register_c_prot_mqtt2() — C_PROT_MQTT2¶

The MQTT protocol, broker side and client side (mqtt_tui registers it with its own client gclass and C_EDITLINE, without the broker).

register_c_mqtt_broker() — C_MQTT_BROKER¶

The broker.