open System
open System.Net
open System.Text

module http =

    let createServer (handler:(HttpListenerRequest -> HttpListenerResponse -> Async<unit>)) =

        let listener = new HttpListener()

        listener.Prefixes.Add "http://*:5000/"

        listener.Start()

        let task = Async.FromBeginEnd(listener.BeginGetContext, listener.EndGetContext)

        async {

            while true do

                let! context = task

                Async.Start(handler context.Request context.Response)

        } |> Async.Start

// --------------------------------------------------------------------
// implementation
// --------------------------------------------------------------------
let server = http.createServer (fun request response -> async {

        let txt = Encoding.ASCII.GetBytes("hello")

        response.OutputStream.Write(txt, 0, txt.Length)

        response.OutputStream.Close()
    })

printfn "Press return to exit..."

Console.ReadLine()

    |> ignore