Comment by procarch2019

The point I was making is that PLCs have a software stack. You have to know the software and programming languages defined in IEC 61131-3. For all intents and purposes they are just very repeatable compute in an industrial setting, but if you don’t know ladder logic or how to interface with them you might be SoL. Most don’t have any sort of web interface and if they do it operates outside the controllable logic. Same goes for shells. If you want to program it you typically have to use the vendor software.