nullidentd is intended to be a bare minimum identd server.

The program implements the auth protocol from RFC 1413. This protocol is
used to identify active TCP connections. It depends on the trustworthiness
of the server and as such is completely useless as a method of
identification. Unfortunately some applications still require that an identd
server is available to query about incoming connections. nullidentd
implements the absolute minimum server to allow these applications to
function. It returns a fake response for any request.