mchess-client/lib/connection/ws_connection.dart

import 'package:web_socket_channel/web_socket_channel.dart';

class ServerConnection {
  late WebSocketChannel channel;
  late bool wasConnected = false;
  late int counter = 0;

  static final ServerConnection _instance = ServerConnection._internal();

  ServerConnection._internal() {
    print("ServerConnection._interal constructor is called");
    connect();
  }

  factory ServerConnection() {
    return _instance;
  }

  factory ServerConnection.getInstance() {
    return ServerConnection();
  }

  void send(String message) {
    channel.sink.add('$counter $message');
    counter++;
  }

  void connect() {
    if (wasConnected) channel.sink.close();
    channel = WebSocketChannel.connect(Uri.parse('ws://localhost:8080'));
    wasConnected = true;

    sendPassword();
  }

  void sendPassword() {
    channel.sink.add(
        'pw NC4EjHvRcsltY3ibWuYDH9OXbKgDXppfnHNCi1K4jktMspoeZjBnOPExxCpDms7zmxijoKCSaSlZ1fWclfWr7Q32DJnv2k87Z5uM');
  }
}