Hi there,
Strange issue. I am using a Serial-USB adapter and have found it is being blocked by ESET. I've tried changing com port numbers, disabling then re-enabling, uninstalling then reinstalling drivers (and have the latest drivers from FTDI). If I 'Pause Firewall (Allow all traffic)' then I can receive info from the com port without issue. I have an old laptop that is set up (theoretically identically) to the desktop I have issues with and it allows com port access without a problem. I don't have 'device control' turned on on either machine and both have the latest ESET versions.
I should also note that the com port does exist in Device Manager and have tried to access it via Putty, Tera Term and even wrote a python script (all say 'Access Denied'). It is definitely an ESET (or somehow Defender) issue, not hardware.
Any ideas?
Cheers