A few short years ago, there was a 'falling out' between a couple of the popular radio related software houses, which resulted in a suspension of a couple of programs talking to each other, but quite quickly, a third party coded a solution to fill the void. That's all behind us now, but at the time, it made me curious about how applications, be they from the same suite, or different programs, exchange relevant information. An example of this is WSJT sending a QSO to be logged by your regular station log. One way this is achieved is with UDP.
Wanting to know exactly what was exchanged, I contacted my logbook provider who gave me some good pointers, but as the API part of the software that looked after this data wasn't developed by them, he couldn't elaborate further.
I then happened upon this gentleman Chris Fredericks VK2BYI who had written a paper on the very subject. The article below is in depth and probably beyond a lot of our understandings, but if you are interested, it is a great source of information. I think most of the issues faced at the time have been resolved, so this article should be treated as FYI only!
The 'paper' is reproduced with the expressed authority of the author Chris VK2BYI.