Transfer file to hololens via POST httprequest (error 429)

Hello,

I work on a desktop application to communicate with hololens glasses via httprequest (hololens is connected via USB), especially, I want to read and write files. To do that, I use the following code (code is more readable on stackoverflow) :

    // Consts
    public static readonly string API_FileQuery =
               @"http://{0}/api/filesystem/apps/file";

    public async static void UploadFile(ConnectInfo connectInfo,
                string knownfolderid,
                string packagefullname,
                string path,
                string filePath)
    {
        try
        {
            // Query
            string query = string.Format(API_FileQuery,
                                       connectInfo.IP);
            query += "?knownfolderid=" +
                        Uri.EscapeUriString(knownfolderid);
            query += "&packagefullname=" +
                        Uri.EscapeUriString(packagefullname);
            query += "&path=" +
                        Uri.EscapeUriString(path);

            //  Create http request
            var httpRequest = new HttpClient();

            httpRequest.DefaultRequestHeaders.Clear();
            httpRequest.DefaultRequestHeaders.Authorization =
               new System.Net.Http.Headers.AuthenticationHeaderValue(
            "Basic", EncodeTo64(connectInfo.User + ":" + connectInfo.Password));
            byte[] data = File.ReadAllBytes(filePath);
            ByteArrayContent byteContent =
                    new ByteArrayContent(data);

            HttpResponseMessage resp =
                    await httpRequest.PostAsync(query, byteContent);

            var responseMessage =
                    await resp.Content.ReadAsStringAsync();
        }
        catch (Exception ex)
        {
            //log some problems
        }
    }

    // Helpers
    private static string EncodeTo64(string toEncode)
    {
        byte[] toEncodeAsBytes = Encoding.ASCII.GetBytes(toEncode);
        string returnValue = Convert.ToBase64String(toEncodeAsBytes);
        return returnValue;
    }
}

I already have a GetFile method (same REST API but with GET http request) that works fine and gives me the file I want but the UploadFile method gives me the following response : StatusCode : 429, ReasonPhrase : 'Too Many Requests' (I try to upload a json file).

I don't really understand why I have this error, I just send 1 request (or I'm missing something).

For information, REST API definition can be found there.

Thanks