PC <-> PLC & real time communication

Hi,

I would like to access PLC I/O status in a real mode from PLC.
So, I would like to read & write from PC to PLC.
I would like to use for example Excel or a data base.

Although, I do not want to use 3rd party software. I would like to access data via RJ45 ports. How I can do it ? Basically, I think I need to develop a protocol which will allow me to do it but how ?

Can I do it in Python or C++/C# ?

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