hmm, about different ports, it's funny, but NBD-spec is directly against
different ports for new style negotiation:
A client who wants to use the new style negotiation SHOULD connect on
the IANA-reserved port for NBD, 10809. The server MAY listen on other
ports as well, but it SHOULD use the old style handshake on those.
also, next sentence is strange too:
The server SHOULD refuse to allow oldstyle negotiations on the newstyle
port.
refuse? Refuse to whom? It's a server, who choose negotiation type. Or
this means, that it should refuse to start at all. so refuse to server
admin, not to NBD client? sounds strange. Should it be "Server SHOULD
NOT use the old style on port 10809"?