A server software having both server and client functions?

[hiraga]

Hi,

I'm looking for a news server software for linux which can be
accessed from an ordinal news client, and can be set up without
changing any configuration of its ancestor news server or
being registered on the server.

That is, such a news server software which retrieves news articles
from its ancestor news server from time to time as a news client and
responds to its clients as an ordinal news server.

TIA
hiraga