Check internet connection on Flutter

check_internet_connection.dart

import 'dart:developer' as developer;
import 'dart:io';

const _lookupHost = 'example.com';

/// Web servers to check.
const _hosts = [
  'example.com',
  'ya.ru',
  'google.com',
];

/// DNS servers to check.
const _dnsAddresses = [
  /// Yandex DNS server
  '77.88.8.8',
  '77.88.8.1',

  /// Google DNS server
  '8.8.8.8',
  '8.8.4.4',
];

/// Connection timeout.
const _timeout = Duration(seconds: 1);

/// Check Internet connection.
Future<bool> checkInternetConnection() async {
  try {
    final result = await InternetAddress.lookup(_lookupHost);
    if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
      // HTTP checking.
      for (final host in _hosts) {
        final address = (await InternetAddress.lookup(host)).first.address;
        final result = await checkHostReachable(address, 80);
        if (result) {
          return true;
        }
      }
      // DNS checking.
      for (final address in _dnsAddresses) {
        final result = await checkHostReachable(address, 53);
        if (result) {
          return true;
        }
      }
    }
  } on SocketException catch (_, stackTrace) {
    developer.log(
      '$_',
      name: 'checkInternetConnection',
      error: _,
      stackTrace: stackTrace,
    );
  }

  return false;
}

/// Is DNS server with [address] reachable?
Future<bool> checkHostReachable(String address, int port) async {
  Socket? sock;
  try {
    sock = await Socket.connect(
      InternetAddress(
        address,
        type: InternetAddressType.IPv4,
      ),
      port,
      timeout: _timeout,
    )
      ..destroy();
    return true;
  } catch (e) {
    sock?.destroy();
    return false;
  }
}