OPC-UA Client

The Modern Way to Access Data: What is an OPC UA Client?

In the industrial automation pyramid, the side that processes and makes sense of data is just as critical as the side where data is collected (the Server). An OPC UA Client is a software application that connects to one or more OPC UA Servers to read data, analyze it, or send commands to field devices.

1. How Does an OPC UA Client Work?

An OPC UA Client operates on a "Request/Response" or "Subscription" logic. Unlike traditional methods, instead of requesting data every single time, a Client can subscribe to specific data points (Tags) on the Server. When a value changes, the Server immediately notifies the Client.

Core Operational Steps:

Endpoint Discovery: The Client reaches the Server via its URL (e.g., opc.tcp://192.168.1.50:4840).
Security Handshake: Certificates and encryption methods (Sign & Encrypt) are exchanged.
Address Space Browsing: The Client views the hierarchy (folders and variables) inside the Server.
Data Exchange: Selected data is read (Read) or written (Write).

2. Types of OPC UA Clients

Depending on the purpose of use, OPC UA Clients appear in different forms:

SCADA/HMI Software: The most common Client type used to visualize factory-wide data.
Data Loggers (Historians): Software that records data into SQL or NoSQL databases for analysis.
Mobile and Web Apps: Modern interfaces used for remote monitoring.
IIoT Gateways (e.g., Hubbox): Hardware that collects field data and converts it into other protocols (MQTT, SQL).

3. The Security Layer: Certificate Management

The biggest difference that sets an OPC UA Client apart from other protocols is security. For a Client to connect to a Server, the following are required:

Application URI: The unique identity of the application.
Certificate Approval: The certificate sent by the Client must be marked as "Trusted" on the Server side.
User Authentication: Access can be restricted using a username and password instead of anonymous login.

4. Using Node-RED as an OPC UA Client

Node-RED, which is built into devices like Hubbox, is an excellent example of an OPC UA Client. Using Node-RED, you can:

See all devices on the network with an OPC UA Browse node.
Pull data using the OPC UA Client node.
Transfer the data you receive directly to a Dashboard or the cloud.

5. Why Should You Use an OPC UA Client?

Reduces Complexity: You collect data through a single standard instead of dozens of different PLC protocols.
Future-Proof: Fully compatible with Industry 4.0 and IIoT standards.
Secure: Your data is transported across the network encrypted rather than as plain text.