I have a line (server-start) in my .emacs for some reasons. Everything is fine when I launch a first session of Emacs, but when I open anther session,
(server-start)
.emacs
Try:
(require 'server) (or (server-running-p) (server-start))
Note that server-running-p does not appear in the manual, so conceivably this could break with future versions of Emacs.
server-running-p