Udp socket in Flutter does not receive anything

If it can help you, here my code for my SocketUDP (as singleton) in my app.I used it in localhost and it works very well :

class SocketUDP {  RawDatagramSocket _socket;  // the port used by this socket  int _port;  // emit event when receive a new request. Emit the request  StreamController<Request> _onRequestReceivedCtrl = StreamController<Request>.broadcast();  // to give access of the Stream to listen when new request is received  Stream<Request> get onRequestReceived => _onRequestReceivedCtrl.stream;  // as singleton to maintain the connexion during the app life and be accessible everywhere  static final SocketUDP _instance = SocketUDP._internal();  factory SocketUDP() {    return _instance;  }  SocketUDP._internal();  void startSocket(int port) {    _port = port;    RawDatagramSocket.bind(InternetAddress.anyIPv4, _port)        .then((RawDatagramSocket socket) {      _socket = socket;      // listen the request from server      _socket.listen((e) {        Datagram dg = _socket.receive();        if (dg != null) {          _onRequestReceivedCtrl.add(RequestConvert.decodeRequest(dg.data, dg.address));        }      });    });  }  void send(Request requestToSend, {bool isBroadCast:false}) {    _socket.broadcastEnabled = isBroadCast;    final String requestEncoded = RequestConvert.encodeRequest(requestToSend);     List<int> requestAsUTF8 = utf8.encode(requestEncoded);    _socket.send(requestAsUTF8, requestToSend.address, _port);  }}