This is a very simple server yet highly reliable solution with ultimate security. It's very useful for small projects and database
access from remote without the need for Internet connection. The operation is like this:
1- Android app in the cellphone sends SMS message to office cellphone.
2- Office cellphone forwards the SMS message to a Bluetooth module connected to a PC through USB-to-Serial adapter
3- Office PC parses and processes the SMS and sends the result back to the Office cellphone through same USB-to-Serial adapter.
4- Office cellphone sends SMS with retrieved data back to remote cellphone.
I have implemented this system in real business application and it's working fine. Since it uses the phone network then the
level of security is very high and no need for encryption.