Remote CODESYS access: how to work on a PLC remotely?

What CODESYS needs

To work on the PLC remotely, the engineering workstation must be able to reach the PLC over the network. Depending on the controller and its configuration, discovery and communications may use different mechanisms and ports. Remote CODESYS access therefore involves more than simple Internet port forwarding.

The most robust approach is to provide the remote workstation with a controlled network path to the equipment, as if it were connected to an authorised maintenance network.

Why conventional remote access can fail

Automatic PLC discovery works easily on a LAN, but not always through routers, NAT or restrictive VPN configurations. In addition, opening CODESYS ports directly on the Internet is not a good maintenance strategy.

A remote link must be authenticated and encrypted, and should make the equipment accessible only to authorised people during the intervention.

Preparing an intervention

Before connecting, you should know the PLC’s IP address, its network mask and the version of the environment being used. If automatic discovery is unavailable remotely, a direct connection to the IP address may be required.

You should also check that the maintenance PC does not have a local network that conflicts with the remote subnet.

CODESYS with RescueLAN

RescueLAN can temporarily establish a remote path to the network containing the PLC through the gateway’s 4G/LTE connection. The goal is not to expose CODESYS to the Internet, but to provide the access required during the maintenance session.

Once the intervention is complete, the remote session is closed. This approach is well suited to automation engineers who already use their usual tools and mainly need a reliable network path between their workstation and the machine.