Use custom server for Fleck websockets

handler.cs

// In the HTTP handler method:
WebSocketConnection connection = null;
connection = new WebSocketConnection(
    new SocketWrapper(response.Socket),
    Accept,
    b => MapRequest(request), // Creates the `WebSocketHttpRequest` from my `request` object
    r => HandlerFactory.BuildHandler(
        r,
        s => connection.OnMessage(s),
        () => connection.Close(),
        (b) => connection.OnBinary(b)));

    // Call the `CreateHandler` method with empty data
    connection.GetType().GetMethod(
        "CreateHandler",
        BindingFlags.Default | BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
        .Invoke(connection, new object[] { Enumerable.Empty<byte>() });
    connection.StartReceiving();

// Methods:
private WebSocketHttpRequest MapRequest(HttpRequest request)
{
    // `request` is my custom object that contains the request data
    var wsRequest = new WebSocketHttpRequest()
    {
        Body = request.Body == null ? "" : Encoding.UTF8.GetString(request.Body),
        Bytes = request.Body,
        Method = request.Method,
        Path = request.Path,
        Scheme = "ws"
    };

    // Headers are stored in a NameValueCollection
    foreach (string key in request.Headers.AllKeys)
        wsRequest.Headers[key] = request.Headers[key];

    return wsRequest;
}

private void Accept(IWebSocketConnection socket)
{
    // Dummy method
    socket.OnMessage = m => Debug.WriteLine(m);
}