Practical guide

OPC UA & PLCs (Siemens TIA Portal)

Modern PLCs can act as an OPC UA server directly, no extra PC needed. That means SCADA, MES, historians and cloud tools read the controller over a secure, standard protocol. Here's how OPC UA fits with PLCs, and how to switch on the server in Siemens TIA Portal.

How OPC UA fits with a PLC

The PLC exposes selected tags/variables in its OPC UA address space. Clients connect, browse, and read/write or subscribe: exactly as with any OPC UA server. Siemens S7-1500 (and S7-1200 in recent firmware) include a built-in OPC UA server; Rockwell, Beckhoff, CODESYS and others offer the same idea with their own tooling.

Enable the OPC UA server on a Siemens S7-1500 / S7-1200

Check licensing. The S7-1500 OPC UA server needs a Siemens runtime license (SIMATIC OPC UA). Confirm it's assigned to the CPU.
In TIA Portal, open the CPU's Properties → OPC UA → Server and tick Activate OPC UA server.
Note or set the server address (endpoint), e.g. opc.tcp://192.168.0.1:4840.
Under Runtime licenses → OPC UA, select the required license type (SE/ME) matching your data volume.
Expose tags: mark the PLC tags/DB variables as accessible from OPC UA (and writable if needed).
Configure security: choose security policies, server certificate, and user authentication (see below).
Compile and download to the CPU. The server starts on the next cycle.

Tip: keep the exposed node set small and stable. Exposing thousands of volatile tags hurts performance and makes clients harder to maintain.

Security on the PLC server

Treat the PLC like any networked server: prefer Sign & Encrypt, install a proper server certificate, and require user authentication rather than anonymous access. First connections usually need the client certificate to be trusted: see OPC UA security & certificates.

Connect a client to test

Open UaExpert (or your client) and add the endpoint opc.tcp://<plc-ip>:4840.
Accept/trust certificates on both sides.
Browse to your exposed tags and subscribe to a value to confirm live updates.

Can't connect? It's almost always the endpoint/IP, a firewall on port 4840, a security-mode mismatch, or certificate trust: the 6 usual causes.

PLC data flowing over OPC UA? Jemba turns it into ranked, costed actions on the floor, no data scientist required.

See Jemba →

FAQ

Does the S7-1200 support OPC UA?

Yes, in recent firmware the S7-1200 includes an OPC UA server (with the appropriate runtime license). The S7-1500 has fuller support.

Do I need a license for the Siemens OPC UA server?

Yes: Siemens requires a SIMATIC OPC UA runtime license (SE or ME depending on features/volume) assigned to the CPU.

Can a PLC be an OPC UA client too?

Many modern PLCs can act as an OPC UA client as well, reading data from other servers: useful for machine-to-machine links.

Last updated 4 September 2026 · Educational resource. Product names are trademarks of their owners; this guide is not affiliated with Siemens.

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