ServerAnnounceObserver Usage? (Documentation)

[IonicOwl]

I'm looking at ways of getting map render progress to be broadcast to the server, as per
http://docs.overviewer.org/en/latest/config/

The two ways of doing this mentioned in the above documentation are using the RConObserver or the ServerAnnounceObserver. I've successfully set up the RConObserver, but I wanted to see if the ServerAnnounceObserver was any better for what I need. The problem is that the documentation seems pretty vague on its usage, specifically this part about specifying the target:

target=<file handle to write to>
Either a FIFO file or stdin. Progress and status messages will be written to this handle.

Can someone provide some more information on how to set this up? I'm not sure exactly what a target is in the context of a Minecraft server (except when using command blocks in-game). How does the observer know where the server is to send messages to it? Do I need to configure anything on the Minecraft server? Is RCon required? It's not mentioned in that section.

[CounterPillow]

Probably needs the stdin handle of the minecraft server process, somewhere in /proc. Not really sure why we still have this though since it's way more fragile than sending stuff over rcon. RCon is preferred.

[IonicOwl]

Ah ok, I guess that makes a little more sense. If RCon is the preferred solution then I'll keep using that anyway. I might still have a play with it though.