My project is constrained in that the Linux side must be a standalone executable (from cmd line) that can write the received data to a file descriptor. However this is not my area of expertise and hence I'm asking for advice; what protocol would you suggest, implemented in what language (on Linux) and do you have a cheap and cheerful example for esp and Linux.
Anyway, I don't want anyone spending lots of time researching this, as I can do that myself, but please reply if you have something to hand that helps me further along.
Failing that, I will research this myself and post my findings/solution when I have it, as reference for others in the future. My default will most likely be Java (Arduino Processing, then exported) and UDP, but that's just a bit of a guess right now.