Hi Haskell Cafe, When I start a web server (http-server:Network.HTTP.Server.serverWith) on a separate thread (async:Control.Concurrent.Async.withAsync) and then try to retrieve a response from the server (HTTP:Network.Browser.*) on a threaded runtime, I see either - connection refusals or - deadlock. Before I sink time into reading the source of the packages in question, does anybody see what's wrong with the code below? Increasing the timeout to wait for the server to initialize doesn't solve the problem. Using a bound thread doesn't solve the problem. I'm compiling with options "-threaded -rtsopts -with-rtsopts=-N". Thank you for taking a look. --Patrick This test project is on github. https://github.com/plredmond/http-server-test-hs/blob/master/src/Lib.hs module Lib ( someFunc ) where import Control.Monad.IO.Class (liftIO) import qualified Control.Concurrent as Concurrent import qualified Control.Concurrent.Async as Async import qualified Control.Exception as Exception import qualified Data.Maybe as Maybe import qualified Network.Browser as Browser import qualified Network.HTTP as HTTP import qualified Network.HTTP.Server as Server import qualified Network.HTTP.Server.Logger as ServerL import qualified Network.HTTP.Server.Response as ServerR import qualified Network.URI as URI someFunc :: IO (Either Exception.SomeException (URI.URI, HTTP.Response String)) someFunc = do Async.withAsync (Server.serverWith config handler) $ \_ -> do Concurrent.threadDelay . round $ 2e6 Exception.try . Browser.browse . Browser.request . Browser.defaultGETRequest $ uri where uri = Maybe.fromJust . URI.parseURI $ "http://localhost:8080/" config = Server.Config ServerL.stdLogger "localhost" 8080 handler _ url req = return (ServerR.respond ServerR.OK :: Server.Response String)