warp- A fast, light-weight web server for WAI applications.

Safe HaskellNone




A fast, light-weight HTTP server handler for WAI.


Run a Warp server

run :: Port -> Application -> IO ()Source

Run an Application on the given port. This calls runSettings with defaultSettings.

runSettings :: Settings -> Application -> IO ()Source

Run an Applicatoin with the given Settings.

runSettingsSocket :: Settings -> Socket -> Application -> IO ()Source

Same as runSettings, but uses a user-supplied socket instead of opening one. This allows the user to provide, for example, Unix named socket, which can be used when reverse HTTP proxying into your application.

Note that the settingsPort will still be passed to Applications via the serverPort record.

runSettingsConnection :: Settings -> IO (Connection, SockAddr) -> Application -> IO ()Source

Allows you to provide a function which will return a Connection. In cases where creating the Connection can be expensive, this allows the expensive computations to be performed in a separate thread instead of the main server loop.

Since 1.3.5

runSettingsConnectionMaker :: Settings -> IO (IO Connection, SockAddr) -> Application -> IO ()Source

Allows you to provide a function which will return a function which will return Connection.


data Settings Source

Various Warp server settings. This is purposely kept as an abstract data type so that new settings can be added without breaking backwards compatibility. In order to create a Settings value, use defaultSettings and record syntax to modify individual records. For example:

 defaultSettings { settingsTimeout = 20 }

defaultSettings :: SettingsSource

The default settings for the Warp server. See the individual settings for the default value.


settingsPort :: Settings -> IntSource

Port to listen on. Default value: 3000

settingsHost :: Settings -> HostPreferenceSource

Default value: HostIPv4

settingsOnException :: Settings -> Maybe Request -> SomeException -> IO ()Source

What to do with exceptions thrown by either the application or server. Default: ignore server-generated exceptions (see InvalidRequest) and print application-generated applications to stderr.

settingsOnExceptionResponse :: Settings -> SomeException -> ResponseSource

A function to create Response when an exception occurs.

Default: 500, text/plain, "Something went wrong"

Since 2.0.3

settingsOnOpen :: Settings -> IO ()Source

What to do when a connection is open. Default: do nothing.

settingsOnClose :: Settings -> IO ()Source

What to do when a connection is close. Default: do nothing.

settingsTimeout :: Settings -> IntSource

Timeout value in seconds. Default value: 30

settingsManager :: Settings -> Maybe ManagerSource

Use an existing timeout manager instead of spawning a new one. If used, settingsTimeout is ignored. Default is Nothing

settingsFdCacheDuration :: Settings -> IntSource

Cache duratoin time of file descriptors in seconds. 0 means that the cache mechanism is not used. Default value: 10

settingsBeforeMainLoop :: Settings -> IO ()Source

Code to run after the listening socket is ready but before entering the main event loop. Useful for signaling to tests that they can start running, or to drop permissions after binding to a restricted port.

Default: do nothing.

Since 1.3.6

settingsNoParsePath :: Settings -> BoolSource

Perform no parsing on the rawPathInfo.

This is useful for writing HTTP proxies.

Default: False

Since 2.0.3


exceptionResponseForDebug :: SomeException -> ResponseSource

Default implementation of settingsOnExceptionResponse for the debugging purpose. 500, text/plain, a showed exception.

Data types

data HostPreference

Which host to bind.

Note: The IsString instance recognizes the following special values:

  • * means HostAny
  • *4 means HostIPv4
  • !4 means HostIPv4Only
  • *6 means HostIPv6
  • !6 means HostIPv6Only

type Port = IntSource

TCP port number.

data ConnSendFileOverride Source

Whether or not ConnSendFileOverride in Connection can be overridden. This is a kind of hack to keep the signature of Connection clean.



Don't override

Override Socket

Override with this Socket


data Connection Source

Data type to manipulate IO actions for connections.




connSendMany :: [ByteString] -> IO ()
connSendAll :: ByteString -> IO ()
connSendFile :: FilePath -> Integer -> Integer -> IO () -> [ByteString] -> IO ()

filepath, offset, length, hook action, HTTP headers

connClose :: IO ()
connRecv :: IO ByteString
connBuffer :: Buffer
connBufferSize :: BufSize
connSendFileOverride :: ConnSendFileOverride

socketConnection :: Socket -> IO ConnectionSource

Default action value for Connection.



warpVersion :: StringSource

The version of Warp.

Data types

data InternalInfo Source

Internal information.

type HeaderValue = ByteStringSource

The type for header value used with HeaderName.

type IndexedHeader = Array Int (Maybe HeaderValue)Source

Array for a set of HTTP headers.

requestMaxIndex :: IntSource

The size for IndexedHeader for HTTP Request. From 0 to this corresponds to "Content-Length", "Transfer-Encoding", "Expect", "Connection", "Range", and "Host".

Time out manager

File descriptor cache

withFdCache :: Int -> (Maybe MutableFdCache -> IO a) -> IO aSource

Creating MutableFdCache and executing the action in the second argument. The first argument is a cache duration in second.

getFd :: MutableFdCache -> FilePath -> IO (Fd, Refresh)Source

Getting Fd and Refresh from the mutable Fd cacher.

data MutableFdCache Source

Mutable Fd cacher.

type Refresh = IO ()Source

An action to activate a Fd cache entry.


withDateCache :: (DateCache -> IO a) -> IO aSource

Creating DateCache and executing the action.

data DateCache Source

The type of the cache of the Date header value.

type GMTDate = ByteStringSource

The type of the Date header value.

Request and response



:: Settings 
-> Connection 
-> InternalInfo 
-> SockAddr

Peer's address.

-> Source IO ByteString

Where HTTP request comes from.

-> IO (Request, IndexedHeader, IO (ResumableSource IO ByteString))

Request passed to Application, IndexedHeader of HTTP request for internal use, and leftover source (i.e. body and other HTTP reqeusts in HTTP pipelining).

Receiving a HTTP request from Connection and parsing its header to create Request.



:: Connection 
-> InternalInfo 
-> (forall a. IO a -> IO a)

Restore masking state.

-> Request

HTTP request.

-> IndexedHeader

Indexed header of HTTP request.

-> Response

HTTP response including status code and response header.

-> IO Bool

Returing True if the connection is persistent.

Sending a HTTP response to Connection according to Response.

Applications/middlewares MUST specify a proper ResponseHeaders. so that inconsistency does not happen. No header is deleted by this function.

Especially, Applications/middlewares MUST take care of Content-Length, Content-Range, and Transfer-Encoding because they are inserted, when necessary, regardless they already exist. This function does not insert Content-Encoding. It's middleware's responsibility.

The Server header is added if not exist in HTTP response header.

There are three basic APIs to create Response:

responseFile :: Status -> ResponseHeaders -> FilePath -> Maybe FilePart -> Response
HTTP response body is sent by sendfile(). Applications are categorized into simple and sophisticated. Simple applications should specify Nothing to Maybe FilePart. The size of the specified file is obtained by disk access. Then Range is handled. Sophisticated applications should specify Just to Maybe FilePart. They should treat Range (and If-Range) by thierselves. In both cases, Content-Length and Content-Range (if necessary) are automatically added into the HTTP response header. If Content-Length and Content-Range exist in the HTTP response header, they would cause inconsistency. Status is also changed to 206 if necessary.
responseBuilder :: Status -> ResponseHeaders -> Builder -> Response
HTTP response body is created from Source. Typically, Transfer-Encoding: chunked is used. If Content-Length is specified, Transfer-Encoding: chunked is not used.
responseSource :: Status -> ResponseHeaders -> Source IO (Flush Builder) -> Response
HTTP response body is created from Builder. Typically, Transfer-Encoding: chunked is used. If Content-Length is specified, Transfer-Encoding: chunked is not used.