You just beat me. I haven't tested any of this beyond compiling it, so there are probably as many bugs as lines of code, but I figured I'd throw it out there before I went to bed. I had a much more complicated design going for a long time then decided to cut it down as much possible—quite possibly too far. First, I added a 'method missing' analogue, ProtocolMissing, to etsn.Server, whose handler gets any connection whose protocol isn't in its registry. Second, I added a command https://github.com/JImmyFrasche/etsn/tree/master/etsnsrv It only registers a ProtocolMissing handler. Whenever it gets a request it tries to open a file and if it's a domain socket it sends the fd down it. Finally I added another library https://github.com/JImmyFrasche/etsn/tree/master/etsnunix that provides a convenient method for registering protocols with etsnsrv(1) with an interface somewhat like a pared down version of etsn. Like I said, I just made sure it compiled so it probably doesn't work right, if at all—and I know there are a few places where it does outright obviously the wrong thing—but should serve as a sketch, till I knock the bugs off it and get a better idea of where to tidy it up. Perhaps the protocol, or lack of one, is too simplistic, but no reason not to try the simplest possible solution first.