Minimal asynchronous CL web server
Common Lisp
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Minimal asynchronous Common Lisp web server

:house started out as part of the :deal project ("deal"? "house"? get it?). I hacked it out in an attempt to generalize it and use it other projects with similar objectives. It's intentionally minimal, single-threaded and stresses readability over efficiency both in its internals and in the interfacing code it requires.


  • There is now a *cookie-domains* variable that expects a list of strings representing domains where cookies should be valid. It defaults to nil. If left unset, house will do the default thing and set one cookie for the default domain. If you set it to a list of strings, it will explicitly emit domain= tags for cookies, and send the cookie token for each specified domain. (Shamelessly adding features for congregate here :p)
  • The default write! method now outputs CORS headers by default (and there is no way to turn it off at the moment)
  • Handlers now accept, and properly handle path parameters. For instance, (define-handler (hello-world/-user=string :content-type "text/plain") (format nil "Hello there, ~a!" user)) will define a handler that accepts requests for /hello-world/<some path component>, runs the usual checks ensuring that it's a valid string, and binds its value to the symbol user. The body of that handler will do exactly what you think it should.
  • Handlers now accept, and properly handle HTTP methods as an additional keyword parameter. Additionally, this can be set to :any (in which case the defined handler will handle any HTTP method). For instance (define-handler (hello-world :method :get) ...) will create a handler that will only respond to GET requests, and nots POSTs, DELETEs or others.
  • Handlers no longer expose the symbol parameters. Instead, they expose the symbol request (you can call (parameters request) to get the old parameters value). This is in the interest of supporting dispatch based on the :host header, but can also allow some other tricks.
  • Added redirect! primitive so that normal handlers can conditionally redirect to other pages
  • Fixed the buffering system so that slow POST requests that pause between headers and body are now handled properly
  • define-closing-handler and define-stream-handler have now been merged into define-handler. The new macro now has a :close-socket? keyword param that defaults to t.


  • If you haven't already done so, install quicklisp.
  • Clone this repo into quicklisp/local-projects/.
  • Hop into your lisp and run (ql:quickload :house)


Quick start
(define-handler (hello-world :content-type "text/plain") ()
  "Hello world!")
(define-handler (hello-you/-name=string) ()
  (format nil "Hello there, ~a!" name))
(house:start 4040)

You should then be able to hop over to a browser and visit http://localhost:4040/hello-world to see the plaintext "Hello world!" response, or http:localhost:4040/hello-you/James to see the plaintext "Hello there, James!" (this may or may not make sense to do, depending on whether your name is James).

Threaded quick start

Because :house is single-threaded, using house:start directly as above will monopolize your REPL. You might not care about that in certain circumstances, or perhaps your deployment environment can't afford the extra thread. If you do and it can, you should start :house in a separate thread to retain your ability to evaluate things against the running system. You can do that the usual way:

(defparameter *server* (bordeaux-threads:make-thread (lambda () (house:start 4040))))
Static Files

House is not a file server. Static file serving capability is provided for ease of testing, and maybe for very small-scale deployment. If you're going to be taking any significant traffic, get a reverse proxy going with something like nginx.

You can define a static file handler with

(define-file-handler [file-or-directory])

It'll handle individual files by serving them, and it'll handle directories by serving all contained files recursively.


You can set up re-directors with

(define-redirect-handler (name :permanent? t) "/static/name.html")

Requests for "/name" will now instead serve a 301 Moved Permanently response with a target of "/static/name.html" (if you leave out :permanent? t, it'll be a 307 Temporary Redirect instead). House isn't optimized for redirecting, either from the performance or the notation perspective. If you're going to be re-directing any significant number of pages, consider having your reverse proxy handling that too.

Using the type annotations

You can specify desired argument types for your handlers. For example:

(define-handler (handler) ((foo :json) (bar :integer)))

You can then use bar as an integer and foo as a parsed JSON s-expression in the body of that handler. The built-in types are :string, :integer, :json, :keyword, :list-of-keyword and :list-of-integer. If you need a more specific type, you can use define-http-type. For example:

(define-http-type (:game)
     :type-expression `(gethash ,parameter *game-table*)
     :type-assertion `(typep ,parameter 'game))

Once that's done, you can annotate parameters with the :game label.

(define-handler (handler) ((foo :game) ...) ...)

foo will then be looked up in *game-table*, and assert-http-ed to be of type 'game before the handler body is evaluated.

It's also possible to enforce arbitrary properties of parsed parameters. For instance

(define-handler (handler) ((foo :integer (>= 64 foo 2) (evenp foo)))

ensures that foo will be an even integer between 2 and 64 (inclusive).

All this is entirely optional. If you don't care about it, just pass un-annotated arguments to your handlers, and they'll do exactly what you'd expect. You'll then be able to handle the type-conversion/assertions entirely manually.

External API



Takes a port-number and starts the server listening on that port.



Defines a handler. The handler body has access to three bound symbols in addition to its parameters:

  • sock: the requesting socket (should only really be used for subscribe! calls, but you can also write things to it if you need to send stuff before the request proper)
  • session: the session belonging to the requesting user
  • request: the raw request object, with exported accessors resource, headers session-tokens and paramteres.
    • paramters contains the raw alist of incoming HTTP parameters
    • resource contains the raw URI, minus host and parameters
    • headers contains the raw HTTP headers alist (of particular interest is the :host key)
    • session-tokens contains the raw list of session tokens associated with this request

Depending on the keyword parameter :close-socket?, it may or may not close the incoming TCP stream after it responds.


Defines a closing handler that responds with "application/json", and automatically JSON-encodes its response.


Defines a handler that sends either 301 or 307 HTTP responses (permanent redirect and temporary redirect respectively).


Defines a handler that very inefficiently responds with static files.

Event Streams


Subscribes the specified socket to the specified channel. Should only be used with stream handlers, since the socket will need to be kept open for a subscription to be relevant.


Publishes a message to all subscribers of the specified channel.

The rest is still TODO.



Handler types