Basic read-only HTTP file server HttpListener

using System;
using System.IO;
using System.Net;

class HttpFileServer
{
    private static HttpListenerResponse response;
    private static HttpListener listener;
    private static string baseFilesystemPath;

    static void Main(string[] args)
    {
        if (!HttpListener.IsSupported)
        {
            Console.WriteLine(
                "*** HttpListener requires at least Windows XP SP2 or Windows Server 2003.");
            return;
        }

        if(args.Length < 2)
        {
            Console.WriteLine("Basic read-only HTTP file server");
            Console.WriteLine();
            Console.WriteLine("Usage: httpfileserver <base filesystem path> <port>");
            Console.WriteLine("Request format: http://url:port/path/to/file.ext");
            return;
        }

        baseFilesystemPath = Path.GetFullPath(args[0]);
        var port = int.Parse(args[1]);

        listener = new HttpListener();
        listener.Prefixes.Add("http://*:" + port + "/");
        listener.Start();

        Console.WriteLine("--- Server stated, base path is: " + baseFilesystemPath);
        Console.WriteLine("--- Listening, exit with Ctrl-C");
        try
        {
            ServerLoop();
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex);
            if(response != null)
            {
                SendErrorResponse(500, "Internal server error");
            }
        }
    }

    static void ServerLoop()
    {
        while(true)
        {
            var context = listener.GetContext();

            var request = context.Request;
            response = context.Response;
            var fileName = request.RawUrl.Substring(1);
            Console.WriteLine(
                "--- Got {0} request for: {1}", 
                request.HttpMethod, fileName);

            if (request.HttpMethod.ToUpper() != "GET")
            {
                SendErrorResponse(405, "Method must be GET");
                continue;
            }

            var fullFilePath = Path.Combine(baseFilesystemPath, fileName);
            if(!File.Exists(fullFilePath))
            {
                SendErrorResponse(404, "File not found");
                continue;
            }

            Console.Write("    Sending file...");
            using (var fileStream = File.OpenRead(fullFilePath))
            {
                response.ContentType = "application/octet-stream";
                response.ContentLength64 = (new FileInfo(fullFilePath)).Length;
                response.AddHeader(
                    "Content-Disposition",
                    "Attachment; filename=\"" + Path.GetFileName(fullFilePath) + "\"");
                fileStream.CopyTo(response.OutputStream);
            }

            response.OutputStream.Close();
            response = null;
            Console.WriteLine(" Ok!");
        }
    }

    static void SendErrorResponse(int statusCode, string statusResponse)
    {
        response.ContentLength64 = 0;
        response.StatusCode = statusCode;
        response.StatusDescription = statusResponse;
        response.OutputStream.Close();
        Console.WriteLine("*** Sent error: {0} {1}", statusCode, statusResponse);
    }
}