Why Your MQTT Dashboard Jumps Backward: Timestamps, Sequence Numbers and Replay
MQTT arrival order is not process order. Why the DUP flag misses the duplicates that hurt, Sparkplug's 8-bit seq wrap, and MQTT 5.0 fixes for stale state.
Articles
Practical SCADA notes
Field-oriented references for HMI/SCADA systems, industrial communication, alarms, tags, historians, and project delivery.
Use MQTT Shared Subscriptions to Scale Consumers — but Keep the Historian Out of the Pool
Shared subscriptions split an MQTT stream across workers — and will quietly halve your historian feed and scramble trend order if you point them wrong.
How to Size an MQTT Wildcard Subscription Before It Floods Your Historian
Estimate the real load behind site/# and contain it with MQTT 5.0: Retain Handling, shared subscriptions, Receive Maximum and SUBACK reason codes.
MQTT Client IDs Are Only Guaranteed to 23 Bytes: ACL Planning for SCADA Edge
Duplicate client IDs, wildcard ACL rules nobody owns, retained commands that re-fire, and silent denied publishes. What MQTT guarantees at the SCADA edge.
MQTT Payload Schema Versioning for SCADA Edge
Versioning MQTT telemetry payloads so historians, HMI clients, MES connectors and analytics survive a field change instead of breaking on one.
Rotating an MQTT Broker Certificate Without Dropping Your SCADA Clients
A staged plan for rotating MQTT broker, client and CA certificates without breaking publishers, store-and-forward queues or Sparkplug birth sequences.
How to Keep MQTT Store-and-Forward From Punching Holes in Your Historian
Why an MQTT edge gateway loses data during a WAN outage, and how to buffer with source timestamps, sequence numbers and a replay policy that holds.
MQTT QoS and Retained Message Notes for SCADA
Practical notes for choosing MQTT QoS levels, retained messages, clean sessions, and duplicate handling in SCADA and industrial telemetry projects.
Telling a Dead MQTT Gateway from a Quiet One on the HMI
Using Last Will, birth messages and retained state so a SCADA screen shows offline, stale and healthy as three things — not one green icon that lies.
Designing Sparkplug B Topics You Won't Have to Rename Later
Laying out Sparkplug B group, edge node and device IDs — plus birth certificates, aliases and STATE — so a rename doesn't break every subscription.
OPC UA vs MQTT
How to think about OPC UA and MQTT in industrial systems without turning the comparison into a vendor argument.