http request working in dart but not flutter

Question

I have a python http server per https://realpython.com/python-http-server/#how-to-start-pythons-httpserver-in-the-command-line

It's working fine in pure dart:

import 'package:http/http.dart' as http;

main() async {
  var url = Uri.http('192.168.0.140:8000', 'whatsit/create');
  var response =
      await http.post(url, body: {'name': 'doodle', 'color': 'blue'});
  print('Response status: ${response.statusCode}');
  print('Response body: ${response.body}');
}

so I make an identical function in my Flutter app and call it from a button:

  getRequest() async {
    var url = Uri.http('192.168.0.140:8000', 'whatsit/create');
    var response =
        await http.post(url, body: {'name': 'doodle', 'color': 'blue'});
    print('Response status: ${response.statusCode}');
    print('Response body: ${response.body}');
  }

and it throws and XMLHttpRequest error.

I know I should probably be using https but I don't understand why it runs in pure dart but not flutter.