MQTT
MQTT (Message Queuing Telemetry Transport) is a lightweight protocol designed for real-time messaging using a publish/subscribe model. OIBus acts as an MQTT client using the MQTT.js library to interact with MQTT brokers.
Specific Settings
Connection
| Setting | Description | Example Value |
|---|---|---|
| URL | Address of the MQTT broker. Accepts mqtt://, mqtts://, tcp://, tls://, ws://, or wss:// (use mqtts:///tls:// for Certificate authentication). Default port is 1883. | mqtt://broker.example.com:1883 |
| Reconnect period | Time (in milliseconds) to wait before reconnection attempts | 5000 |
| Connect timeout | Maximum time (in milliseconds) to wait for connection establishment | 30000 |
| Reject unauthorized | Reject connections with unverified certificates (e.g., self-signed) | Enabled/Disabled |
Quality of Service
| Setting | Description | Example Value |
|---|---|---|
| QoS | Quality of Service level: 0 (at most once), 1 (at least once, possible duplicates), 2 (exactly once). | 0, 1, 2 |
| Persistent | When enabled, the broker retains messages and queued deliveries across reconnections (requires QoS 1 or 2). When disabled, a clean session is started. | Enabled/Disabled |
Authentication
No Authentication
| Setting | Description | Example Value |
|---|---|---|
| (None) | No authentication required for connection | - |
Username / Password
| Setting | Description | Example Value |
|---|---|---|
| Username | Username for broker authentication | mqtt_user |
| Password | Password for broker authentication | •••••••• |
Certificate Authentication
| Setting | Description | Example Value |
|---|---|---|
| Cert file path | Path to the signed certificate file | /path/to/cert.pem |
| Key file path | Path to the private key file | /path/to/key.pem |
| CA file path | Path to the certificate authority file. Required for Certificate authentication. | /path/to/ca.pem |
Data Throttling
| Setting | Description | Example Value |
|---|---|---|
| Number of messages before flush | Number of messages to accumulate before flushing to North caches | 1000 |
| Delay between flush | Time delay (in milliseconds) between automatic flushes of accumulated messages | 1000 |
Item Settings
Each item subscribes to one MQTT topic. MQTT uses a hierarchical topic structure with wildcard support:
| Setting | Description | Example Value |
|---|---|---|
| Topic | The MQTT topic to subscribe to. Wildcards supported. | sensors/#, plant/+/T |
Topic Wildcards
| Setting | Description | Example Value |
|---|---|---|
# | Multi-level wildcard | sensors/# |
+ | Single-level wildcard | sensors/+/temperature |
Use the tester below to see which topics a given subscription filter matches:
Topic tree
▸factory/
▸line1/
○temperature✅
○pressure✅
▸line2/
○temperature✅
○pressure✅
○humidity✅
▸alerts/
▸line1/
○overheat
▸line2/
○overheat
5 of 7 topics matched
Examples