详细描述

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");

vlink::Publisher::create_unique
static UniquePtr create_unique(const std::string &url_str, InitType type=InitType::kWithInit)
Heap-allocates a Publisher and wraps it in a std::unique_ptr.
Definition: publisher-inl.h:39

vlink::Subscriber::create_unique
static UniquePtr create_unique(const std::string &url_str, InitType type=InitType::kWithInit)
Heap-allocates a Subscriber and wraps it in a std::unique_ptr.
Definition: subscriber-inl.h:39

注解: 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].