Whilst this work is all great, there are many variables to consider… especially considering the type of dongle/bearer etc…
I would push for a Gammu Addon instead… https://github.com/pajikos/sms-gammu-gateway … use the right tools for the right job and don’t try to re-invent the wheel… or do, but then don’t complain about breaking changes down the line… but as i started off by saying… well done on the hard work and getting this working…