3 files changed, 16 insertions, 3 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 7bf9a1c36c4..d4acdd3f84e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1237,8 +1237,9 @@ passing the hook functions as arguments to a "wrapping" function.
 *** New macro `with-wrapper-hook' for running an abnormal hook as a
 set of "wrapping" filters, similar to around advice.
 
-** `server-eval-at' is provided to allow evaluating forms on different
-Emacs server instances.
++++
+** The new function `server-eval-at' allows evaluation of Lisp forms on
+named Emacs server instances, using TCP sockets.
 
 +++
 ** `call-process' and `call-process-region' allow a `(:file "file")' spec
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 4290c5e820d..9a4132fa3a6 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,8 @@
 2012-02-02  Glenn Morris  <rgm@gnu.org>
 
+        * server.el (server-auth-dir): Doc fix.
+        (server-eval-at): Doc fix.  Give an explicit error if !server-use-tcp.
+
         * subr.el (run-mode-hooks): Doc fix.
 
 2012-02-02  Juri Linkov  <juri@jurta.org>
diff --git a/lisp/server.el b/lisp/server.el
index 9dcd1f3b1d9..a08f971e88c 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -126,6 +126,8 @@ port number."
 
 (defcustom server-auth-dir (locate-user-emacs-file "server/")
   "Directory for server authentication files.
+We only use this if `server-use-tcp' is non-nil.
+Otherwise we use `server-socket-dir'.
 
 NOTE: On FAT32 filesystems, directories are not secure;
 files can be read and modified by any user or process.
@@ -1525,7 +1527,14 @@ only these files will be asked to be saved."
   nil)
 
 (defun server-eval-at (server form)
-  "Eval FORM on Emacs Server SERVER."
+  "Contact the Emacs server named SERVER and evaluate FORM there.
+Returns the result of the evaluation, or signals an error if it
+cannot contact the specified server.  For example:
+  \(server-eval-at \"server\" '(emacs-pid))
+returns the process ID of the Emacs instance running \"server\".
+This function requires the use of TCP sockets. "
+  (or server-use-tcp
+      (error "This function requires TCP sockets"))
   (let ((auth-file (expand-file-name server server-auth-dir))
         (coding-system-for-read 'binary)
         (coding-system-for-write 'binary)