Reading the signal strength MC8795

I am using MC8795 modem on an embedded linux system, and would like to get the signal strength.
The modem is mapped as /dev/ttyUSB3 and works fine, but when I send a command to that port to read the signal strength it response with :
" Could not write to COM device. (1)"
The reason is that the interface is already used by another process which manages the modem communication.This model has no other ports that can except AT command, out of the six USB port created when connected.

Can anyone suggest me a way to read the signal strength in order to display it on the management page.

We should not open and use same tty port concurrently, e.g. only 1 application can access same port in 1 time.

Guess either the system’s or your modem manager is accessing the ttyUSB3 port?

Normally, we can also get signal strength via +CSQ command on PDP port (e.g. ttyUSB4) or using Sierra SDK via CnS port.

Hope it helps.