Using SLIME over an SSH tunnel

If you’d like to use emacs on one computer (i.e. your windows box at home) and use SLIME to connect to a Common Lisp process on a remote computer (i.e. your server at work), here’s how I do it.

First, create a startup file for your favorite Lisp implementation.

lisp startup file

(require 'asdf)
(asdf:oos 'asdf:load-op 'swank)
; start swank
(setf swank:*use-dedicated-output-stream* nil)
(setf swank:*communication-style* :fd-handler)
(swank:create-server :dont-close t)

Now edit your ~/.emacs so that you’ve got something like the following in it:


(require 'slime)
(require 'tramp)
(add-hook 'lisp-mode-hook (lambda () (slime-mode t)))
(add-hook 'inferior-lisp-mode-hook (lambda () (inferior-slime-mode t)))
(setq lisp-indent-function 'common-lisp-indent-function
      slime-complete-symbol-function 'slime-fuzzy-complete-symbol)
;;; If you want to tunnel through an intermediate host, such as your
;;; work firewall, use the following couple lines.  If you're using a
;;; Windows emacs, use 'plink' as below, otherwise substitute 'ssh'.
 '("\\.work-domain\\.com" nil "/"))
 '("firewall\\.work-domain\\.com" nil nil))
(defvar *my-box-tramp-path*
(defvar *current-tramp-path* nil)
(defun connect-to-host (path)
  (setq *current-tramp-path* path)
  (setq slime-translate-from-lisp-filename-function
    (lambda (f)
      (concat *current-tramp-path* f)))
  (setq slime-translate-to-lisp-filename-function
    (lambda (f)
      (substring f (length *current-tramp-path*))))
  (slime-connect "localhost" 4005))
(defun my-box-slime ()
  (connect-to-host *my-box-tramp-path*))
(defun my-box-homedir ()
  (find-file (concat *server-tramp-path* "/home/me/")))

Now, load up the startup file you created on your host Lisp to start the swank server. Then, create an ssh tunnel, i.e. ssh -L 4005:localhost:4005

Now you can M-x my-box-slime to connect through your SSH tunnel to your work box; SLIME’s M-. command will also correctly open up the file containing the defun of whatever’s under your cursor, and C-c C-k works correctly, etc. If you want to open up some lisp file, M-x my-box-homedir is a convenient shortcut.

For Windows users

If you’re using Windows and want to also use a multi-hop tramp method (i.e. ssh into your work firewall, and then ssh from there to your server at work), be aware that tramp 2.1.4 and prior has a bug; it’s fixed in CVS and probably 2.1.5, which is not out yet. Information and a patch is available here.

You’ll also want to use plink from the PuTTY distribution in lieu of ssh. If you’re doing multi-hop tramp, though, you need to use plink for the first hop (Windows box -> “firewall” box) and ssh thereafter (“firewall” -> “server”).