No, there's no such thing.

Both the client and the server were originally one program (xtrek),
written by university students and researchers.  There was no
specification; the original program and the derivatives grew by
gradual accretion.

There is later documentation for the server and the protocol, and
you'll find them in the server source.  The daemon documentation uses
doxygen format.  The protocol is a plain text description.

There are clients using Python, Java, and JavaScript if you'd like to
understand better with those languages.

Meanwhile, it's probably time you learned C, or you won't be able to
understand anything inside Netrek.  The best way to learn C is to
write in it.

James Cameron