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Hunchensocket - WebSockets for Hunchentoot

Hunchensocket is a Common Lisp implementation of WebSockets realized as an extension to [Edi Weitz'] edi excellent Hunchentoot web server. Hunchensocket implements a compliant RFC6455 server.

Note that Alexander Kahl, the original author, has desactivated his old version that only supports the drafts of the protocol.

Installation

Hunchensocket is in Quicklisp, so if you have that setup just do (ql:quickload :hunchensocket).

Quicklisp is also good to use the trunk alongside with other dependencies, perhaps to test a new feature or a bugfix:

$ cd ~/Source/Lisp/
$ git clone https://github.com/joaotavora/hunchensocket.git

(push "~/Source/Lisp" ql:*local-project-directories*)
(ql:quickload :hunchensocket) ;; use local hunchensocket and pull
                              ;; dependencies from quicklisp

A chat server in 30 lines

First define classes for rooms and users. Make these subclasses of websocket-resource and websocket-client.

(defpackage :my-chat (:use :cl))
(in-package :my-chat)

(defclass chat-room (hunchensocket:websocket-resource)
  ((name :initarg :name :initform (error "Name this room!") :reader name))
  (:default-initargs :client-class 'user))

(defclass user (hunchensocket:websocket-client)
  ((name :initarg :user-agent :reader name :initform (error "Name this user!"))))

Define a list of rooms. Notice that hunchensocket:*websocket-dispatch-table* works just like hunchentoot:*dispatch-table*, but for websocket specific resources.

(defvar *chat-rooms* (list (make-instance 'chat-room :name "/bongo")
                           (make-instance 'chat-room :name "/fury")))

(defun find-room (request)
  (find (hunchentoot:script-name request) *chat-rooms* :test #'string= :key #'name))

(pushnew 'find-room hunchensocket:*websocket-dispatch-table*)

OK, now a helper function and the dynamics of a chat room.

(defun broadcast (room message &rest args)
  (loop for peer in (hunchensocket:clients room)
        do (hunchensocket:send-text-message peer (apply #'format nil message args))))

(defmethod hunchensocket:client-connected ((room chat-room) user)
  (broadcast room "~a has joined ~a" (name user) (name room)))

(defmethod hunchensocket:client-disconnected ((room chat-room) user)
  (broadcast room "~a has left ~a" (name user) (name room)))

(defmethod hunchensocket:text-message-received ((room chat-room) user message)
  (broadcast room "~a says ~a" (name user) message))  

Finally, start the server. hunchensocket:websocket-acceptor works just like hunchentoot:acceptor, and you can probably also use hunchensocket:websocket-ssl-acceptor.

(defvar *server* (make-instance 'hunchensocket:websocket-acceptor :port 12345))
(hunchentoot:start *server*)

Now open two browser windows on https://www.piesocket.com/websocket-tester enter ws://localhost:12345/bongo as the host and play around chatting with yourself.

License

See COPYING for license details.

Design

Main sources of inspiration:

• Original implementation by Alexander Kahl, which cleverly hijacks the Hunchentoot connection after the HTTP response and keeps the connection alive, just like in a Head request.
• clws's API because it explicitly defines websocket "resources"
• Hunchentoot's's API because it uses CLOS

Contributing

• Propose patches using GitHub's pull request feature, as usual. You may ping the maintainers if you don't get some kind of feedback after a week or so.

• When composing a PR, it's OK to include nonessential cleanup/housekeeping changes like fixing the odd bug, typo, or indentation mishap. But please segregate these changes into their own separate commit. You may freely git rebase --interactice and git push -f to rewrite your PR if needed.

• Each commit's message should strictly follow the GNU ChangeLog format described here. It's what the Emacs project uses. There's a short subject line in the imperative form, followed optionally by longer explanatory text, all formatted to less than 70 columns. A bit like a nice text email from the twentieth century. In the end there are entries for each file and function/macro/top-level entity changed within it, along with very brief descriptions of the change. You can use C-x 4 a in Emacs to help you generate these, if you want.

  Here are some examples:

Closes #12: Avoid bordeaux-threads bug when nullifying locks

Elias Mårtenson noticed that its default implementation, the
BT:WITH-LOCK-HELD macro evaluates its argument twice and thus
nullifying that slot while holding it is not only unnecessary, but
problematic.

See https://github.com/joaotavora/hunchensocket/pull/12.

This fix is conceptually cleaner than the one proposed there.

* hunchensocket.lisp (call-with-new-client-for-resource): Don't
  nullify client's WRITE-LOCK while locking it.

Fix many bugs and add automatic tests for robustness.

* hunchensocket-tests.lisp: New file.

* hunchensocket.asd (:hunchensocket-tests): New system.
(:hunchensocket): Depends on cl-fad.

* hunchensocket.lisp (control-frame-p): New function.
(websocket-client): Separate input and output stream slots. State
goes in client.
(check-message): Receive fragment and total length.
(send-text-message): Use SEND-FRAME.
(close-connection, send-frame): New functions.
(websocket-error): Add error status reader.
(with-new-client-for-resource): Adapt to separate stream slots.
(read-unsigned-big-endian): Fix big bug. Was reading little-endian!
(read-frame): Optionally read payload. Error out when control
frame is too large.
(read-frame-from-client): New function.
(mask-unmask): New function.
(read-application-data): New function.
(handle-frame): Rework completely. Bigger but slightly easier to
read.
(read-handle-loop): Simplify.
(process-request): Use new WITH-NEW-CLIENT-FOR-RESOURCE.