Just got a Solis inverter, and found that the com port uses a plug that I do not have. So, I made two different versions. The nut-19mm-2.stl file is just remnants of that first version, and not needed for final design, just included in case someone has ideas for a design improvement.

incub77 has shared the source code for the actual communication on github here: https://github.com/incub77/solis2mqtt