300+ SCADA Protocol Articles & Guides
Deep dives on Modbus, DNP3, IEC 60870-5-101/104, IEC 61850, OPC UA, Profinet, MQTT, IEC 62443, and substation automation — written for practicing engineers.
MQTT 5 Session & Message Expiry Intervals Explained
How MQTT 5 session and message expiry intervals work: bounding stored session lifetime and per-message TTL, with the values, defaults, and broker behavior explained.
MQTT Over WebSockets Explained: Browsers, Ports, TLS
How MQTT over WebSockets works: the WebSocket handshake, MQTT subprotocol negotiation, default ports 80/443, secure WebSockets with TLS, and browser MQTT clients.
What's New in MQTT 5? Features, Changes & Why Upgrade
MQTT 5.0 explained: foundational changes (properties, reason codes, Clean Start, AUTH packet), new features, why the version jumped from 3.1.1 to 5, and migration notes.
MQTT Keep Alive & Client Take-Over Explained
How MQTT keep alive works: PINGREQ and PINGRESP packets, the half-open connection problem, the 1.5x detection rule, and client take-over on ClientId reconnect.
MQTT Last Will and Testament (LWT) Explained
How MQTT Last Will and Testament works: the will message, will topic, will QoS and retain, when the broker publishes the will, and the will + retained pattern.
MQTT Retained Messages Explained: Last Known Value
How MQTT retained messages work: the retain flag, storing the last value on a topic, wildcard delivery, QoS interactions, clearing retained messages, and patterns.
MQTT Persistent Sessions & Message Queuing Explained
How MQTT persistent sessions and message queuing work: clean session flag, session present flag, what the broker stores, client state, and MQTT 5 changes.
MQTT QoS Levels Explained: QoS 0, 1 and 2
How MQTT QoS levels work: QoS 0 at most once, QoS 1 at least once, QoS 2 exactly once, the handshakes, QoS downgrade, packet identifiers and choosing a level.
MQTT Topics and Wildcards Explained
How MQTT topics and wildcards work: topic levels, single-level (+) and multi-level (#) wildcards, $SYS topics, matching rules, and topic naming best practices.
MQTT Clients, Brokers & Connection Establishment Explained
How MQTT clients and brokers work and how a connection is established: the CONNECT and CONNACK packets, every field, return codes, NAT and keep alive.
MQTT Publish, Subscribe & Unsubscribe: Packets Explained
How MQTT publish, subscribe and unsubscribe work: the PUBLISH, SUBSCRIBE and UNSUBSCRIBE packets, every field, and the SUBACK and UNSUBACK acknowledgements.
MQTT Publish/Subscribe Pattern Explained: How Pub/Sub Works
How the MQTT publish/subscribe pattern works: decoupling, the broker's role, message filtering, scalability, and how pub/sub differs from message queues.
What Is MQTT? Protocol Architecture, Packets & How It Works
MQTT is a lightweight publish/subscribe protocol for IoT. Learn its architecture, packet structure, QoS, sessions, security and how the protocol works.
Wireshark MQTT: Decode Industrial IoT Traffic
Wireshark MQTT capture and decode: display filters, CONNECT and PUBLISH packets, QoS levels, Sparkplug B payloads, TLS on 8883, and broker troubleshooting.
OPC UA Pub/Sub: Complete Technical Guide for Engineers
OPC UA Pub/Sub explained — classic subscriptions, Part 14 broker model, MQTT/AMQP transport, UADP encoding, TSN integration, and Client/Server vs Pub/Sub.
OPC UA vs MQTT vs Modbus: Which Protocol Should You Use?
OPC UA vs MQTT vs Modbus: Which protocol fits your project? Compare security, speed, data modeling, and scalability to pick the right one for your IIoT system.