XBoard protocol documentation wanted (chess) [closed]

Question

I am looking for XBoard documentation. XBoard is a communication protocol between chess engines and chess GUIs.

I know about http://www.gnu.org/software/xboard/engine-intf.html , but seem to miss what a engine has to send/receive for communication with a board.

Anything better then the advice to reverse engineer the protocol either from a GUI Implementation (e.g.: xchess or eboard) or a chess engine would be great. Even a commented snippet from a board/engine communication might help.

Answer 1

From the comments:

Your link tells us that H.G.Muller is the current maintainer of the interface. His page shows the minimal interface you need to implement.