Transfer file to hololens via POST httprequest (error 429)

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 :

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

    // Classes & Structs
    public struct ConnectInfo
    {
        public ConnectInfo(string ip, string user, string password)
        {
            IP = ip;
            User = user;
            Password = password;
        }

        public string IP;
        public string User;
        public string Password;
    }

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

            HttpResponseMessage resp = await httpRequest.GetAsync(query);

            byte[] responseMessage = await resp.Content.ReadAsByteArrayAsync();

        }
        catch (Exception ex)
        {
            //log some problems
        }

    }



    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;
    }
}

To run it I call

BuildDeployPortal.ConnectInfo co = new BuildDeployPortal.ConnectInfo("127.0.0.1:10080", "user", "pass");

//get file
BuildDeployPortal.GetFile(co, "LocalAppData", "2017-01-25-09-04-21_TestFile.csv", "app_full_package_name", "\\LocalState");

//upload file
BuildDeployPortal.UploadFile(co, "LocalAppData", "app_full_package_name", "\\LocalState",
            "C:\\Users\\myuser\\Desktop\\info.json");

The GetFile method works fine and gives me the file I want but the UploadFile method gives me the following response : StatusCode : 429, ReasonPhrase : 'Too Many Requests'. Same result if I only run one of its during execution.

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