'transports': ['polling','websocket'] cant work

[HnLong]

Hi guys:
in my client as below:

import 'dart:async';
import 'package:socket_io_client/socket_io_client.dart' as IO;

main() {
IO.Socket socket = IO.io('http://127.0.0.1:8090/xy', <String, dynamic>{
'transports': ['polling','websocket'],
'extraHeaders': {'foo': 'bar'}
});
socket.on('connect', () {
print('socket_io_client===>connect http://127.0.0.1:8090/xy');
socket.emit('msg', 'init');
int count = 0;
new Timer.periodic(const Duration(seconds: 20), (Timer countDownTimer) {
socket.emit('msg', count++);
});
});
socket.on('event', (data) => print(data));
socket.on('disconnect', () => print('disconnect http://127.0.0.1:8090/xy'));
socket.on('fromServer', () => print());
}

pubspec.yaml
#socketIO
socket_io_common: ^0.9.0+5
socket_io_client:
git:
url: https://github.com/rikulo/socket.io-client-dart

and my socket server version is "socket.io": "2.0.4"(also try with "2.3.0") on the nodejs server.
now issue: the client cant conn to the server. but if transports replace with 'transports': ['websocket'],it work ok.so how to fix it in my project? thx very much!

[jumperchen]

Are you using it in Flutter env.? if so, there is no dart:html api available in Flutter, so it can only work with websocket transports in either dart:html (for Web) or dart:io(for Flutter).

[HnLong]

  sure in Flutter env. yeh the README.md has explain that,i was careless.thanks chen!