gnuclient
Allows you to attach to an already running Emacs
gnuserv allows you to attach to an already running Emacs. This
allows external programs to make use of Emacs' editing
capabilities. It is like GNU Emacs' emacsserver/server.el, but
has many more features.
You do not need this package if you use XEmacs; it already
includes gnuserv and gnuclient. If you want to use gnuserv with
both GNU Emacs and XEmacs, you will only be able to use the
alternative /usr/bin/gnuclient with one flavor of emacs; you will
have to use either gnuclient.xemacs or gnuclient.emacs for the
other flavor.