I have a client with a windows computer on a yacht. It has up to 1-3 working internet connections depending on where the boat is. One connection is via a satellite link (the most reliable, but slowest at 256kbits/sec), another is a dedicated cell phone link (~1Mbit/sec on a good day in a good location), and the 3rd is a wifi connection if the marina happens to have one (often the fastest connection, but frequently unavailable).
I would like to connect each of these to the computer through its own Ethernet connection. Then I would like to have some software on the windows machine (which I could purchase or write) that would select a "best" connection and route internet traffic through it.
I think of this as a custom ISP failover problem. I'm aware that there are some hardware solutions, but I would prefer a commercial software solution over hardware, and best of all, I would prefer to write my own software in C++ or Python. Then I would know what it was really doing.
I'm looking for commercial software solution, or resources to get me started on writing my own.