Android Question NFC: is it possible to do this with B4A?

I'm not even sure you can do it! period!

A NFC tag is a passive device, meaning that it will only give info when powered by the reading device (using rf).
The NFC reader/writer present in smartphones are active devices, meaning that they give the NFC tags power.
To be able to "emulate" an NFC would require hardware specific solutions, that I don't believe are yet available in mass consuming electronics. (I may be wrong)

I have tested such "emulators" (several of them) with a few of my available phones, like Samsung S6 and Samsung X-Cover3.
Reading/writing is no issue, but no emulation is done.

dead this
https://developer.android.com/guide/topics/connectivity/nfc/hce.html

Thank You, I didn't know this...

The solution to pay with Smartphone means that it is able to simulate a passive RFID. It's the best seller of the banks' commercials today

But how to do it with b4a ?

https://stackoverflow.com/questions/10831994/how-to-emulate-a-nfc-tag-on-an-android-phone never tried

here we need Erel support

There is currently no library that implements the host card emulation.