can't connect to MongoDB with flutter/dart

I have an app I am building in flutter and want to connect it to a database in mongo, but can't for the life of me get it to connect, here is a simple dart code to troubleshoot:

it always returns the error:

Unhandled exception: MongoDB ConnectionException: Could not connect to 127.0.0.1:27017 HandshakeException: Connection terminated during handshake

import 'package:mongo_dart/mongo_dart.dart';
import 'dart:io';

//Platform.environment['MONGO_DART_DRIVER_HOST']
//final mongoURI = Platform.environment['MONGO_DART_DRIVER_HOST'];

final url = "mongodb://127.0.0.1:27017/labelmask";

main() async {
  Db _db = new Db(url);
  await _db.open(secure: true);
  print('connected');
}

Here is what I tried:

-I have tried using dart:io and get Platform.environments, but returned null

-Tried to connect to admin db instead of 'labelmask', same error

-I started first mongod and then mongo

-I can connect to this Database using python(pymongo) and from Compass GUI

-I can run mongo commands in terminal so I know it is connected, just not with dart