All interaction between southbound drivers and the admin/data centers flows through the EMQX message bus, following MQTT 5.0. Custom drivers and third-party integrations can talk directly using the topics below.
| Item | Default |
|---|
| Address | tcp://localhost:1883 (TLS on 8883) |
| Account / password | unihh / unihh |
| Broker | EMQX 5.x, shared subscriptions and retained messages supported |
| Category | Topic | Publisher | Consumer | Description |
|---|
| Driver registration | iot/driver/register | Driver | Admin center | Driver broadcasts its metadata and HTTP endpoint at startup |
| Driver heartbeat | iot/driver/heartbeat | Driver | Admin center | Every 5s by default, with active channel metrics |
| Driver status / last-will | iot/driver/{driverCode}/status | Driver / EMQX | Admin center | Online/offline notices; the broker publishes the LWT will on crash (retained=true) |
| Device config sync | iot/device/config/update | Admin center | All drivers | Global hot notice for device or point changes |
| Dedicated device config | iot/driver/{driverCode}/device/config | Admin center | Target driver | Directed push of connection and point definitions |
| Point data upload | iot/driver/{driverCode}/data | Driver | Data center | Periodic acquisition results, consumed via shared subscription |
| Write-back command | iot/driver/{driverCode}/cmd | Admin center | Target driver | Point write (WRITE) or service invocation (SERVICE) |
| Device channel state | iot/device/status | Driver | Admin center | Physical link drop/recovery; platform updates device state |
- Shared subscriptions: the
iot/driver/+/data stream is consumed with an MQTT 5.0 shared subscription, so multiple data-center instances can split the throughput; - Dedicated topics: config sync and commands use
{driverCode}-scoped topics, so unrelated drivers never process extra traffic; - Retained messages: driver status is retained, so late subscribers learn the latest state immediately.
| Mechanism | Description |
|---|
| LWT last-will | Drivers register a will on connect; EMQX publishes the offline message if the process dies |
| Heartbeat watchdog | Platform-side safety net: a driver is declared offline after 15s without a heartbeat |
| Channel mutex | Drivers apply a fair lock per device channel — commands arriving concurrently on MQTT still execute serially on the wire |
Third-party systems (e.g. an MES) that only consume data can share-subscribe to iot/driver/+/data directly. For issuing control, prefer the platform REST API (/api/v1/devices control endpoints) over publishing raw MQTT: you get authentication, parameter snapshots and the complete execution audit trail for free.
