I got the not terribly helpful error message recently trying to connect
emacsclient to a emacs daemon using tcp sockets.
emacsclient: error accessing server file "server"
Looking at the source, its not obvious what is going wrong - http://git.savannah.gnu.org/cgit/emacs.git/tree/lib-src/emacsclient.c?h=emacs-24#n1356
(I tried to recompile emacs and attach a gdb, but I didn't have much luck with that)