An example win32 service in F#

I needed a small single purpose TCP socket server for work, and I thought it might be an opportune time to try a new programming language. My choices were Scala, F# or Erlang. The target platform was a win2k box and I wanted to be able to register it as a service so F# was the obvious choice. In the code below I modified the echo server example from the MIT F# site to run as a service.

// This sample code is provided "as is" without warranty of any kind. 
// We disclaim all warranties, either express or implied, including the 
// warranties of merchantability and fitness for a particular purpose. 

#light
#r "System.ServiceProcess.dll";;
#r "System.Configuration.Install.dll";;


// Echo Server: opens a service on the localhost which bounces data straight back  

open System.Net
open System.Net.Sockets
open System.Threading
open System.ServiceProcess
open System.ComponentModel
open System.Configuration.Install
open Microsoft.FSharp.Compatibility.CompatArray

let spawn f = (new Thread(new ThreadStart(f))).Start()

type EchoServer = class
    inherit ServiceBase as base
    
    new() as this = {} then base.ServiceName <- "SimpleEchoService"
    
    override this.OnStart(args:string[]) = 
        spawn(this.listen)
            
    member this.listen() =
        let sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP) 
        sock.Bind(new IPEndPoint(IPAddress.Any, 5120))

        let backlog = 2 // number of incoming connections that can be queued for acceptance
        sock.Listen(backlog)

        let port = (sock.LocalEndPoint :?> IPEndPoint).Port 
        Printf.printf "server accepting on port %d...\n" port

        while (true) do
            let csock = sock.Accept() 
            Printf.printf "the server has accepted a client on port %d...\n" port;
            spawn(fun () -> 
                let total = ref 0 
                try 
                    let buf = Bytearray.create 64
                    let stream = new NetworkStream(csock) 
                    while true do
                        Printf.printf "server reading...\n";
                        let nread = stream.Read(buf,0,64) 
                        Printf.printf "server read %d...\n" nread;
                        stream.Write(buf,0,nread);
                        total := !total + nread;
                    done;
                with 
                    | :? Sockets.SocketException 
                    | :? System.IO.IOException -> 
                        Printf.printf "client gone: server read %d bytes from that client\n" !total;
                        flush stdout
            )
        done

end

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