Happstack.Server

Happstack.Server provides a self-contained HTTP server and a rich collection of types and functions for routing Requests, generating Responses, working with query parameters, form data, and cookies, serving files and more.

A very simple, "Hello World!" web app looks like:

import Happstack.Server
main = simpleHTTP nullConf $ ok "Hello World!"

By default the server will listen on port 8000. Run the app and point your browser at: http://localhost:8000/

At the core of the Happstack server we have the simpleHTTP function which starts the HTTP server:

simpleHTTP :: ToMessage a => Conf -> ServerPart a -> IO ()

and we have the user supplied ServerPart (also known as, ServerPartT IO), which generates a Response for each incoming Request.

A trivial HTTP app server might just take a user supplied function like:

myApp :: Request -> IO Response

For each incoming Request the server would fork a new thread, run myApp to generate a Response, and then send the Response back to the client. But, that would be a pretty barren wasteland to work in.

The model for ServerPart is essential the same, except we use the much richer ServerPart monad instead of the IO monad.

For in-depth documentation and runnable examples I highly recommend The Happstack Crash Course http://happstack.com/docs/crashcourse/index.html.

HTTP Server

parseConfig :: [String] -> Either [String] Conf

Parse command line options into a Conf.

simpleHTTP :: ToMessage a => Conf -> ServerPartT IO a -> IO ()

start the server, and handle requests using the supplied ServerPart.

This function will not return, though it may throw an exception.

NOTE: The server will only listen on IPv4 due to portability issues in the Network module. For IPv6 support, use simpleHTTPWithSocket with custom socket.

simpleHTTP' :: (ToMessage b, Monad m, Functor m) => (UnWebT m a -> UnWebT IO b) -> Conf -> ServerPartT m a -> IO ()

A combination of simpleHTTP'' and mapServerPartT. See mapServerPartT for a discussion of the first argument of this function.

NOTE: This function always binds to IPv4 ports until Network module is fixed to support IPv6 in a portable way. Use simpleHTTPWithSocket with custom socket if you want different behaviour.

simpleHTTP'' :: (ToMessage b, Monad m, Functor m) => ServerPartT m b -> Request -> m Response

Generate a result from a ServerPartT and a Request. This is mainly used by CGI (and fast-cgi) wrappers.

simpleHTTPWithSocket :: ToMessage a => Socket -> Conf -> ServerPartT IO a -> IO ()

Run simpleHTTP with a previously bound socket. Useful if you want to run happstack as user on port 80. Use something like this:

import System.Posix.User (setUserID, UserEntry(..), getUserEntryForName)

main = do
    let conf = nullConf { port = 80 }
    socket <- bindPort conf
    -- do other stuff as root here
    getUserEntryForName "www" >>= setUserID . userID
    -- finally start handling incoming requests
    tid <- forkIO $ simpleHTTPWithSocket socket Nothing conf impl

Note: It's important to use the same conf (or at least the same port) for bindPort and simpleHTTPWithSocket.

see also: bindPort, bindIPv4

simpleHTTPWithSocket' :: (ToMessage b, Monad m, Functor m) => (UnWebT m a -> UnWebT IO b) -> Socket -> Conf -> ServerPartT m a -> IO ()

Like simpleHTTP' with a socket.

bindPort :: Conf -> IO Socket

Bind port and return the socket for use with simpleHTTPWithSocket. This function always binds to IPv4 ports until Network module is fixed to support IPv6 in a portable way.

bindIPv4

Arguments

:: String

IP address to bind to (must be an IP address and not a host name)

-> Int

port number to bind to

-> IO Socket

Bind to ip and port and return the socket for use with simpleHTTPWithSocket.

import Happstack.Server

main = do let conf = nullConf
              addr = "127.0.0.1"
          s <- bindIPv4 addr (port conf)
          simpleHTTPWithSocket s conf $ ok $ toResponse $
            "now listening on ip addr " ++ addr ++
            " and port " ++ show (port conf)

waitForTermination :: IO ()

Wait for a signal. On unix, a signal is sigINT or sigTERM (aka Control-C).

On windows, the signal is entering: e return

Request Routing

module Happstack.Server.Routing

Creating Responses

module Happstack.Server.Response

Looking up values in Query String, Request Body, and Cookies

module Happstack.Server.RqData

Create and Set Cookies (see also Happstack.Server.RqData)

module Happstack.Server.Cookie

File Serving

module Happstack.Server.FileServe

HTTP Realm Authentication

module Happstack.Server.Auth

Error Handling

module Happstack.Server.Error

I18N

module Happstack.Server.I18N

Web-related Monads

module Happstack.Server.Monads

Output Validation

module Happstack.Server.Validation

HTTP Types

module Happstack.Server.Types