why post request on djoser /users endpoint from httpurlconection in android app returns 401 error?

Question

I have an API which allows post request to register new users. I'm using djoser library for authentication in the API. It works in browser but when I try making this post request in my android project.I get 401 unauthorized response, I don't know what is wrong with my request!?

    private static String makeHttpRequest(URL url, String info) throws IOException {
    String jsonResponse = "";
    if (url == null) {
        return jsonResponse;
    }

    HttpURLConnection urlConnection = null;
    OutputStream outputStream = null;
    InputStream inputStream = null;

    try {

        urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.setRequestMethod("POST");
        urlConnection.setRequestProperty("Content-Type", "application/json");
        urlConnection.setRequestProperty("Accept", "application/json");
        urlConnection.setDoOutput(true);
        //write to the stream
        outputStream = urlConnection.getOutputStream();
        byte[] input = info.getBytes(Charset.forName("UTF-8"));
        outputStream.write(input, 0, input.length);
        urlConnection.connect();

        //read the response
        if (urlConnection.getResponseCode() == 200) {
            authenticated = true;
            inputStream = urlConnection.getInputStream();
            jsonResponse = readFromStream(inputStream);
        } else {
            Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
        }
    } catch (IOException e) {
        Log.e(LOG_TAG, "Problem retrieving the JSON results.", e);
    } finally {
        if (urlConnection != null) {
            urlConnection.disconnect();
        }
        if (inputStream != null) {
            inputStream.close();
        }
        if (outputStream != null) {
            outputStream.close();
        }
    }
    return jsonResponse;
}