mqtt_conf.h File Reference

Transport configuration for the mqtt:// MQTT broker bridge. More...

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Detailed Description

Transport configuration for the mqtt:// MQTT broker bridge.

MqttConf binds the mqtt:// URL scheme to the Eclipse Paho MQTT C client. MQTT is a lightweight publish/subscribe protocol designed for constrained devices, intermittent links, and low-bandwidth wide-area networks; it always routes through a broker (no peer-to-peer mode). Use this transport to bridge VLink topics to a cloud / fleet MQTT broker, or to interoperate with existing MQTT-based telemetry pipelines.

Supported Node Types

Publisher	Subscriber	Server	Client	Getter	Setter
yes	yes	yes	yes	yes	yes

URL Format

mqtt://<address>[?event=<name>&domain=<N>&qos=<0|1|2>][#<broker_uri>]

Component	Description
address	MQTT topic path (URL host concatenated with path)
event	Optional secondary event filter (?event=)
domain	Domain / namespace identifier (?domain=); factory default applied
qos	MQTT QoS level 0, 1 or 2 (?qos=); factory default applied
fragment	Optional broker URI override carried in the URL fragment

Broker Connection

Property	Source	Description
Broker URI	VLINK_MQTT_BROKER env var	tcp:// / ssl:// / ws:// URI
Domain ID	VLINK_MQTT_DOMAIN env var	Default ?domain= when absent
QoS level	VLINK_MQTT_QOS env var	Default 0, 1 or 2
Keep-alive (s)	VLINK_MQTT_KEEPALIVE env	MQTT keep-alive interval
Client ID prefix	VLINK_MQTT_CLIENT_ID env	Prefix used for generated client IDs

TLS Configuration

Property	Description
ssl:// URI scheme	Selects TLS transport instead of plain TCP
CA certificate file	Configured through set_property("mqtt.ca_file", path)
Client certificate	Configured through set_property("mqtt.cert_file", path)
Client private key	Configured through set_property("mqtt.key_file", path)
Username / password	Set via mqtt.username and mqtt.password properties

Example

// Defaults inherit broker URI and QoS from environment variables:
auto pub = vlink::Publisher<MyMsg>::create_unique("mqtt://telemetry/state?qos=1");
 
// Override broker URI via URL fragment:
auto sub = vlink::Subscriber<MyMsg>::create_unique("mqtt://telemetry/state#tcp://10.0.0.5:1883");

Note

Compiled only when VLINK_SUPPORT_MQTT is defined.

URL parsing uses MqttFactory::get_default_domain_id() and MqttFactory::get_default_qos() when domain or qos are omitted; direct construction defaults remain domain=0 and qos=1.

is_valid() returns false when address is empty, domain is negative, or qos is outside [0, 2].