Snap Notes

raw-http-serve.hs

{-# LANGUAGE OverloadedStrings #-}
------------------------------------------------------------------------------
-- | This example shows 'rawHttpServe', which use "raw" handlers, instead of
-- 'Snap' handlers.
--
-- (It is built using the "commandline" branch from the `snap-server`
-- repository.)
--
-- 'ServerConfig' is a record containing logging functions, users hooks and
-- some low-level HTTP server options.
--
-- 'CmdlineConfig' is a record containing things such as hostname, listen
-- address and port, whether to use SSL or compression.
--
-- Some values in 'ServerConfig' are derived from 'CmdlineConfig' using the
-- 'toServerConfig' function. That function also starts to listen for
-- incoming connections and returns an `accept` function.
--
-- 'rawHttpServe' uses a given handler, the derived 'ServerConfig' together
-- with the `accept` function.
module Main (main) where
   
------------------------------------------------------------------------------
import           Snap.Core                               (Snap, emptyResponse)
import qualified Snap.Internal.Http.Server.Cleanup       as Cleanup
import           Snap.Internal.Http.Server.Types         (ServerHandler)
import           Snap.Http.Server                        (emptyServerConfig, rawHttpServe)
import           Snap.Http.Server.CmdlineConfig          (CmdlineConfig, defaultCmdlineConfig, setBind, setPort, toServerConfig)

------------------------------------------------------------------------------
main :: IO ()
main = Cleanup.runCleanup $ do
    [(_, config, accept)] <- toServerConfig emptyServerConfig cmdlineConfig
    rawHttpServe handler [(config, accept)]
  where
    cmdlineConfig :: CmdlineConfig Snap a
    cmdlineConfig = (setBind "0.0.0.0" . setPort 8000) defaultCmdlineConfig

handler :: ServerHandler ()
handler config session request = return (request, emptyResponse)

snap-notes.md

The Snap Framework is divided in a few libraries:

• snap-core provides the core types and functions to write handlers, i.e. read requests and produce responses.
• snap-server is a library providing a HTTP server, using handlers written with snap-core to serve clients.
• snap provides a convenience module re-exporting snap-core and snap-server, but also the Snaplet API to build Snap applications in a modular way. Notet that snap-server alone (without snap), is enough to write an application.
• io-streams is a streaming IO library. It is not strictly part of Snap Framework but is central to it. For instance you can consume a request's body as an InputStream ByteString.
• io-streams-haproxy implements the PROXY protocol useful to place a HTTP server being proxies (e.g. HAProxy or Stunnel). Just like openssl-streams, you don't use it directly.
• openssl-streams allows snap-server to use HTTPS instead of HTTP.