A connection from a java program to MySQL is, apparently (I have it working) trivial. My intention is to have the java server receive the data from UE4, manipulate it as necessary, and then pass it on to MySQL.
The scheme that I have read about is to have the first byte identify the following data. For example, a first byte of 27 would tell the server that the following x bytes are formatted as an inventory item and this would result in a predefined processing of the data.
My thought is that I would also insert a predefined unique player identifier in the data sequence and flags for different operations.
As this server would only deal with player data, an example of my planned data structure would be PlayerIdentifier, Type of Data, Operation, Data in predefined format.
Of course, I’m a long way from a working system, but I’m confident that with the Socket Plugin and the examples in the source code (and much research) that I will eventually get it running.