Is there a serial algorithm for sending commands to COM port ASCII?

Question

Serial port

Good afternoon!
I'm trying to send data to the device in this order:
The host tells the device ENQ (5)
The device gives an answer ACK (6)
I start transmitting data STX (2) Data ETX (3)
And here is a hitch. In theory, the device should give ACK (6) and I I end the EOT (4) session, but no matter how I try to catch
the ACK(6) response, using the condition, it turns out that the host sees the confirmation and sends EOT, but in fact only then I see ACK from the device on the terminal. And the device gives an error like the EOT session was not closed at a certain timing.
There is also a reverse procedure:
The device sends ENQ (5) and the host responds with ACK (6)
As a result, STX data is transmitted (2) ETX data (3)
And if you do not report ACK (6) after that, the device swears that the data did not receive a response.
If, after ETX, ACK is sent, everything is in order.
And so I had a question. Is there a clear clear algorithm for sending a parcel. It is sending that interests me, because receiving works for me. Maybe I'm missing something.

Answer 1

There are many options.
Available with software or hardware flow control.
Take the documentation for the device or hack its protocol.
Unfortunately, there is no single standard.
static.ozone.ru/multimedia/book_file/1005872730.pdf