Secure WebSockets in Haskell.

wss.hs

-- base ==4.7.0.1
-- bytestring ==0.10.4.0
-- connection ==0.2.4
-- network ==2.4.2.3
-- text ==1.1.0.0
-- websockets ==0.9.3.1

import Control.Concurrent (forkIO)
import Control.Monad (forever, void)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Lazy as BL
import Data.ByteString.Lazy (toStrict)
import Data.Text (Text, pack)
import Network.Connection (Connection, ConnectionParams (..), TLSSettings (..),
    connectionGetChunk, connectionPut, connectTo, initConnectionContext)
import Network.Socket (PortNumber (..))
import Network.WebSockets (ClientApp, ConnectionOptions, Headers,
    defaultConnectionOptions, receiveData, runClientWithStream, sendClose,
    sendTextData)
import Network.WebSockets.Stream (makeStream)

main :: IO ()
main = runSecureClient "echo.websocket.org" 443 "/" application

application :: ClientApp ()
application connection = do
    putStrLn "Connected!"

    void . forkIO . forever $ do
        message <- receiveData connection
        print (message :: Text)

    let loop = do
        line <- getLine
        if null line
            then return ()
            else do
                sendTextData connection (pack line)
                loop
    loop

    sendClose connection (pack "Bye!")

runSecureClient :: String -> PortNumber -> String -> ClientApp a -> IO a
runSecureClient host port path app = do
    context <- initConnectionContext
    connection <- connectTo context (connectionParams host port)
    stream <- makeStream (reader connection) (writer connection)
    runClientWithStream stream host path connectionOptions headers app

connectionParams :: String -> PortNumber -> ConnectionParams
connectionParams host port = ConnectionParams
    { connectionHostname = host
    , connectionPort = port
    , connectionUseSecure = Just tlsSettings
    , connectionUseSocks = Nothing
    }

tlsSettings :: TLSSettings
tlsSettings = TLSSettingsSimple
    { settingDisableCertificateValidation = False
    , settingDisableSession = False
    , settingUseServerName = False
    }

reader :: Connection -> IO (Maybe BS.ByteString)
reader connection = fmap Just (connectionGetChunk connection)

writer :: Connection -> Maybe BL.ByteString -> IO ()
writer connection = maybe (return ()) (connectionPut connection . toStrict)

connectionOptions :: ConnectionOptions
connectionOptions = defaultConnectionOptions

headers :: Headers
headers = []

Prior art:

• jaspervdj/websockets#41
• https://gist.github.com/jaspervdj/7198388
• https://gist.github.com/mpickering/f1b7ba3190a4bb5884f3
• https://gist.github.com/elfenlaid/7b5c28065e67e4cf0767

If you landed here looking for secure WebSockets in Haskell, check out my library Wuss. It handles this for you.