MQTT
MQTT is a broker-based publish/subscribe messaging protocol used for telemetry and control. It requires a configured broker, topic permissions, authentication and a chosen transport/security profile.
Scope: MQTT — requirements depend on the selected profile.
protocol · Catalog reviewed 2026-09-27
ControlOpen Standard
Infrastructure Requirements
- Configured broker and clients
- compatible protocol version, topics and permissions
- selected TCP/TLS/WebSocket transport and trust.
Network & Physical Requirements
| Port / allocation | Transport | Connection / signal flow | Feature and requirement | Evidence |
|---|---|---|---|---|
| 1883 (default) | TCP | MQTT client → MQTT broker | Profile requirement · Core MQTT broker connection MQTT over TCP conventional service | Source checked 2026-09-27 Section 4.2: Network Connections (registered TCP ports) |
| 8883 (default) | TCP | MQTT client → MQTT TLS broker | Optional · TLS MQTT over TLS MQTT TLS conventional service | Source checked 2026-09-27 Section 4.2: Network Connections (registered TCP ports) |
| Configured | TCP | MQTT client → WebSocket broker | Optional · WebSocket MQTT over WebSocket Configured ws/wss broker URI | Source checked 2026-09-27 Section 6: Using WebSocket as a network transport |
Gotchas & IT Notes
- ⚠QoS 0/1/2 are MQTT delivery levels, not IP DSCP classes. Retained messages and persistent sessions need deliberate control-system behavior.