MQTT does not behave like a classical message queue, but under specific conditions it can queue messages for clients. That capability is one of the protocol’s most important reliability features for devices on unreliable networks, and it depends entirely on a concept called the persistent session. Understanding when a session is persistent, what the broker stores in it,… Read More »
Quality of Service, almost always written QoS, is the agreement between the sender of a message and its receiver about the guarantee of delivery for that specific message. It is one of MQTT’s defining features and the single biggest reason the protocol works well over networks that are slow, congested, or unreliable. Rather than forcing every application to… Read More »
Topics are how MQTT decides which client receives which message. Because MQTT uses topic-based filtering (sometimes called subject-based filtering), the topic attached to every message is the entire basis for routing: the broker matches published topics against the topic filters that clients have subscribed to, and delivers accordingly. One distinction is worth fixing in your mind from the… Read More »
Once a client has connected to a broker, almost everything it does comes down to three operations: publishing messages, subscribing to topics, and unsubscribing from them. Each operation has its own control packet, and most are confirmed by an acknowledgement packet from the broker. Understanding the fields these packets carry, and the acknowledgements they trigger, is what lets… Read More »
Every MQTT system is built from two kinds of participant: clients and a broker. A client is any device that speaks MQTT; the broker is the central hub that every message passes through. Before any messages can flow, a client must establish a connection to the broker, and that handshake, the CONNECT and CONNACK exchange, carries the settings… Read More »
The single most important idea in MQTT is that clients do not talk to each other directly. They talk through an intermediary, and they do so using a messaging pattern called publish/subscribe, almost always shortened to pub/sub. Every other feature of the protocol, from Quality of Service to retained messages to shared subscriptions, is built on top of… Read More »
MQTT is a lightweight, publish/subscribe network protocol that transports messages between devices. It was built to move small amounts of data across networks where bandwidth is limited, latency is variable, and connections drop without warning. Those constraints, first encountered on remote industrial sites, are exactly the conditions found across the modern Internet of Things, which is why MQTT… Read More »
If you have ever opened Wireshark on a network with Siemens PLCs, you have seen S7comm. It is the language Siemens controllers use to talk to TIA Portal, to WinCC, to SCADA front-ends, and to each other. The protocol has been around since 1994 and it is still the default way to move data in and out of… Read More »
Industrial control systems run the infrastructure that keeps modern life working — electricity, clean water, fuel, food production, and manufacturing. These systems were built for reliability, not for cybersecurity. Most of them use protocols with no authentication, run on operating systems that stopped receiving patches years ago, and sit on networks that were never meant to face external… Read More »
A complete reference for substation engineers comparing the IEC 61850 process bus and station bus — what each bus does, protocols used, hardware requirements, time synchronization needs, redundancy strategies, bandwidth, topology, and procurement considerations Quick Comparison Table Aspect Process Bus Station Bus Purpose Real-time measurement + trip SCADA, configuration, supervisory Replaces Analog CT/VT wiring + binary trips Conventional… Read More »