Every node in an OPC UA address space — every variable, object, method, and data type — has a unique address called a NodeId. When you read a tag value, browse the address space, or call a method, you are using a NodeId. NodeIds are the OPC UA equivalent of register addresses in Modbus or class/instance/attribute paths in… Read More »
OPC UA uses TCP port 4840 by default. This single port carries everything OPC UA does — discovery, session establishment, reading tags, writing values, subscriptions, method calls, and historical data access. Unlike OPC Classic (which used DCOM with dynamic port allocation and was a firewall nightmare), OPC UA uses one well-known port that works cleanly through NAT, proxies,… Read More »
OPC UA Pub/Sub is a communication pattern within the OPC UA standard that allows data to flow from publishers to subscribers without requiring a direct connection between them. A publisher sends data to a message broker or network bus. Any number of subscribers receive that data independently. No handshake. No dedicated session. No request-response cycle. This is fundamentally… Read More »
Every OPC UA interaction starts with a simple concept: a client asks, a server answers. But beneath that simplicity sits a carefully layered architecture that handles discovery, security, sessions, subscriptions, and more — all defined in the IEC 62541 standard. This guide explains how the OPC UA client-server architecture works from the ground up. Whether you’re developing an… Read More »
OPC UA gives machines a common language. But a common language isn’t enough if everyone uses different vocabulary. A packaging machine and a robot arm both “speak” OPC UA — but how they describe themselves, their data, and their capabilities needs to follow a shared standard too. That’s what companion specifications do. They define standardized data models for… Read More »
If you’ve heard the term “OPC UA” thrown around in meetings about factory automation, Industry 4.0, or IIoT — and you’re not sure what it actually means — you’re in the right place. This guide explains OPC UA in plain language. No jargon walls. No assumption that you already know the protocol stack. Just a clear explanation of… Read More »
Most industrial protocols just move numbers. Register 40001 gives you 42.5 — and that’s it. You need a separate spreadsheet to know it’s a temperature, in Celsius, from Tank 01, with an alarm limit at 80°C. OPC UA works differently. It doesn’t just carry data — it carries the meaning of that data. The structure, relationships, types, units,… Read More »
Industrial systems are under attack. Cyberattacks on manufacturing, energy, and critical infrastructure have surged in recent years. Legacy protocols like Modbus and OPC Classic offer zero protection — data travels in plain text with no authentication. OPC UA was designed to fix this. Security isn’t an add-on or a third-party patch. It’s built into the core of the… Read More »
OPC UA services are the operations that make everything happen. When a client reads a temperature value, subscribes to alarms, calls a method on a remote machine, or browses a server’s data structure — it’s using OPC UA services. Services are defined in IEC 62541 Part 4. They’re abstract — meaning the standard describes what each service does… Read More »
If you’ve ever tried to read data from an OPC UA server, you’ve already interacted with the address space — even if you didn’t realize it. The address space is the core of what makes OPC UA different from simpler protocols. It’s not just a flat list of tags. It’s a structured, self-describing map of everything a server… Read More »