[SOLVED] I would like to use nodemcu to send and receive data via TX RX (with industrial PLC - SIMATIC S7-200)

I would like to use nodemcu to send and receive data via TX RX.
But I don’t know how to do it.
I find some code. but it can’t use.

https://examples.blynk.cc/?board=NodeMCU&shield=ESP8266%20WiFi&example=GettingStarted%2FPushData

I want to send some data to the microcontroller.
Such as 16 # 12 (hexadecimal 12) or ‘Hello’
Can give me some code examples?
It’s better to be able to send data with APP

Take a look at this http://forum.arduino.cc/index.php?topic=396450

I need to send something,what should i do?

You are not clear on what you are trying to do…

What data are you wanting to send?

Are you sending it from the MCU to the App or from the App to the MCU?

Or from one MCU to another MCU… If so, are both connected to the same Blynk project in the App or different projects all together?

Why do you need to use serial?

More detail please.

Thanks for your reply, my question has been solved.
I expect the S7-200 to be docked with nodemcu.