Embedded Python Script to route serial data from USB to SMS and back using AT commands

Small project that falls into corporate blind spot. I am responsible for sustaining project management and I need a solution to replace off-the-shelf serial GSM modems which are no longer supported/available. We would like to utilize Digi Internation ([login to view URL]) TransPort line of cellular routers for simplicity. They are embedded devices which allow running custom python files. I need the device, which normally acts as a cellular gateway, to function as a cellular modem. This task is too small for our in-house SW devs to be concerned with as they are busy developing the main software platform which sends messages to the modem. Primary development platform is Digi TransPort WR41, I have one here I can send to you. Final implementation would be run on a TransPort device which supports global cellular frequencies including CDMA while it lasts in the US. Solution should also be applicable to other TransPort devices in the same family. Must interface with Vaisala viewLinc continuous monitoring software, alarm notifications and acknowledgements are sent using AT Hayes modem commands to a PC serial port. The modem must utilize those commands to send and receive SMS only, no voice, no data. AT command functionality has existed in the viewLinc software for multiple versions, must be backwards compatible for customers not willing to upgrade. Python code must be clean and robust as these devices will simply run all the time. Simple as possible configuration of the final solution is desirable for easy setup in a production environment. Detailed information is available from Digi as datasheets, white papers, forums, etc. Code should be sent back for in-house peer review. Some testing in-house is also required to verify the solution. Most important is the Digi TransPort User Guide but it's too big to attach, can be downloaded here: [login to view URL]