A simple, cancellable and stateless Internet Connectivity Checker

An Internet Connectivity Checker :

• Which can test single or multiple endpoints (with configurable concurrency),
• Which do not depends on any protocol (uses Dart's socket connection),
• Which is cancellable and support both global and per endpoint timeouts,
• Which keep it simple. It is stateless.

This package is not meant to be used with Flutter on the Web (check Internet Connection Check for Flutter on the Web below for alternatives).

If you search for a stateful Internet Connectivity Checker, check out these packages :

• ac_connectivity
• internet_connection_checker
• internet_connection_checker_plus

Usage

Test on a single endpoint

final checker = InetConnectivityChecker(
  endpoint: InetEndpoint(host: 'google.com', port: 443),
  // optional timeout. if unspecified the operating system 
  // default connect timeout will be used instead (~120s).
  timeout: const Duration(seconds: 10),
);

// tired of waiting?
// checker.cancel();

final isConnected = await checker.cancelableOperation.value;

Test on multiple endpoints

final checker = InetConcurrentConnectivityChecker(
  endpoints: [
    InetEndpoint(host: '8.8.8.8', port: 53),
    InetEndpoint(host: 'google.com', port: 443),
    InetEndpoint(host: 'github.com', port: 443),
  ],
  
  // optional global timeout. 
  timeout: const Duration(seconds: 10),

  // optional per endpoint timeout. if unspecified the operating 
  // system default connect timeout will be used instead (~120s).
  timeoutPerEndpoint: const Duration(seconds: 10),

  // optionally, define the maximum concurrency (default is 2)
  maxConcurrency: 4,
);

final isConnected = await checker.cancelableOperation.value;

Which endpoints to use?

If you want to test for an Internet connection, you might as well want to use the endpoints that are the less-likely to be down.

The plugin provides the list of all the IPv4 and IPv6 addresses for the root name servers.

Be-aware that it is more than likely that your application will have to be compatible with both IPv4-only and IPv6-only network. My advice is to mix and randomize those two lists and use the concurrent connectivity checker to test for an Internet connection.

final endpoints = [
  ...kRootNameServersIpV4Endpoints,
  ...kRootNameServersIpV6Endpoints,
]..shuffle();

Internet Connection Check for Flutter on the Web

For testing Internet connection for Flutter Web, I recommended that you either use the connectivity_plus plugin :

import 'package:connectivity_plus/connectivity_plus.dart';

final result = await Connectivity().checkConnectivity();

if (result == ConnectivityResult.none) {
  // not connected to the Internet
} else {
  // connected to the Internet
}

Connectivity().onConnectivityChanged.listen((result) {
  // on connectivity changes
});

Or the ac_connectivity package which extend connectivity_plus with Internet connectivity on all platform :

import 'package:ac_connectivity/ac_connectivity.dart';

final cancelableOperation = Connectivity().checkInetConnectivityState(
  timeout: const Duration(seconds: 3),
);

final state = await cancelableOperation.value;

if (state == InetConnectivityState.disconnected) {
  // disconnected (same as ConnectivityResult.none)
} else if (state == InetConnectivityState.connected) {
  // connected to a network without Internet access.
} else if (state == InetConnectivityState.internet) {
  // connected to Internet.
}

Connectivity().listen((state) {
  // on Internet connectivity state changes
});