End of response to an AT command

Question

How to be sure what is end of an AT command send to GSM module?

I need some character or string that represent end of AT command for every case due to finding when

Answer 1

Like you suppose it's \r\n.
This defines the end of a line.

And it makes only sense to process complete lines.

Some commands respons with only OK\r\n, some with some data.
So you should build at first a parser, who can detect complete lines, so they can be processed with a function that handles responses.

Sometimes you can get even responses you don't request, like change events net login or the sim status #QSS: 2\r\n.

So you need to know what answer you expect and wait until you get this