How can I write to a folder in another mvc application with web client c#

Question

I hope someone can advise me on the situation I have. I have two asp mvc applications, one is the desktop and the other the mobile version. I want to be able to write files uploaded on the mobile version to a folder in the desktop version, because this latter holds the administrative section of the application. I can download files from one to the other with the WebClient class of .Net, but I haven't been able to upload files from one to the other. I have a console application to test the uploading and whenever I try it I get an error saying "access is denied" to the folder in the application. I tried creating a folder in the application outside of the App_Data folder because I thought this folder is restricted, but I get the same error. Can someone please advise me what to do? I've read googling here and there that this can be easily solved from the IIS administration, but I doubt the guys in my hosting company will be willing to grant me any rights on the administration of any application. The code I wrote only fails when I try to save the files. Here is the code of the site that receives the request:

[HttpPost]
    [AllowAnonymous]
    public string SubirArchivosRegistro(HttpPostedFileBase file)
    {
        string MensajeError = "";
        string path = "";
        string Success = " El (los) diplomas subidos exitosamente ";
        try
        {

                if (file != null && file.ContentLength > 0)
                {
                    path = Path.Combine(Server.MapPath("~/ArchivosRegistroUsuarios"), file.FileName);

                    file.SaveAs(path);
                    Success += file.FileName +",";
                }
                ///return path;
            return Success;
        }
        catch(Exception ex)
        {
            MensajeError = "Ha ocurrido un error, no se pudieron subir los archivos solicitados "+ex.Message;
            return MensajeError;
        }
    }

And this is the code in the client part (none of the codes is failing, it's just a permissions issue):

try
        {
            WebClient cliente = new WebClient();
            if (GendarmeriaCertNombre != null && GendarmeriaCertNombre.ElementAt(0) != null)
            {
                gendarmeria = new List<Guid?>();
                gendarmeriaNombre = new List<string>();
                foreach (HttpPostedFileBase file in GendarmeriaCertNombre)
                {
                    if (file != null)
                    {
                        string filename = Path.GetFileName(file.FileName);
                        Guid guidnum = _fileStore.SaveUploadedFile(file, "gendarmeria");
                        gendarmeria.Add(guidnum);
                        gendarmeriaNombre.Add(file.FileName);
                        string ruta = _fileStore.GetDiskLocation(guidnum);
                        byte[] respuesta = cliente.UploadFile("http://localhost/DiplomadoEnMandoPolicial/Account/SubirArchivosRegistro", "POST", ruta);
                        response = System.Text.Encoding.ASCII.GetString(respuesta);
                    }

                }
                if (gendarmeria != null && gendarmeria.Count > 0 && gendarmeriaNombre != null && gendarmeriaNombre.Count > 0)
                {
                    registro.GendarmeriaCertificado = String.Join(",", gendarmeria.Select(t => t.Value.ToString("D")));
                    registro.GendarmeriaCertNombre = String.Join(",", gendarmeriaNombre);
                }


            }
            if (CursoInacipeCertNombre != null && CursoInacipeCertNombre.ElementAt(0) != null)
            {
                inacipe = new List<Guid?>();
                inacipeNombre = new List<string>();
                foreach (HttpPostedFileBase file in CursoInacipeCertNombre)
                {
                    if (file != null)
                    {
                        string filename = Path.GetFileName(file.FileName);
                        Guid guidnum = _fileStore.SaveUploadedFile(file, "inacipe");
                        inacipe.Add(guidnum);
                        inacipeNombre.Add(file.FileName);
                        string ruta = _fileStore.GetDiskLocation(guidnum);
                        byte[] respuesta = cliente.UploadFile("http://localhost/DiplomadoEnMandoPolicial/Account/SubirArchivosRegistro", "POST", ruta);
                        response = System.Text.Encoding.ASCII.GetString(respuesta);
                    }
                }
                if (inacipe != null && inacipe.Count > 0 && inacipeNombre != null && inacipeNombre.Count > 0)
                {
                    registro.CursoInacipeCertificado = String.Join(",", inacipe.Select(t => t.Value.ToString("D")));
                    registro.CursoInacipeCertNombre = String.Join(",", inacipeNombre);
                }

            }
            if (CursoCideCertNombre != null && CursoCideCertNombre.ElementAt(0) != null)
            {
                cide = new List<Guid?>();
                cideNombre = new List<string>();
                foreach (HttpPostedFileBase file in CursoCideCertNombre)
                {
                    if (file != null)
                    {
                        string filename = Path.GetFileName(file.FileName);
                        Guid guidnum = _fileStore.SaveUploadedFile(file, "cide");
                        cide.Add(guidnum);
                        cideNombre.Add(file.FileName);
                        string ruta = _fileStore.GetDiskLocation(guidnum);
                        byte[] respuesta = cliente.UploadFile("http://localhost/DiplomadoEnMandoPolicial/Account/SubirArchivosRegistro", "POST", ruta);
                        response = System.Text.Encoding.ASCII.GetString(respuesta);
                    }
                }
                if (cide != null && cide.Count > 0 && cideNombre != null && cideNombre.Count > 0)
                {
                    registro.CursoCideCertificado = String.Join(",", cide.Select(t => t.Value.ToString("D")));
                    registro.CursoCideCertNombre = String.Join(",", cideNombre);
                }
                cliente.Dispose();
            }
        }

Well, that's the problem, I'm open to any suggestions.