perl-Net-Ident -- Lookup the username on the remote end of a TCP/IP connection
http://search.cpan.org/dist/Net-Ident/
Net::Ident is a module that looks up the username on the remote side of
a TCP/IP connection through the ident (auth/tap) protocol described in
RFC1413 (which supersedes RFC931). Note that this requires the remote
site to run a daemon (often called identd) to provide the requested
information, so it is not always available for all TCP/IP connections.