data_connection_checker 0.2.1

Checks for an actual internet connection, by opening a socket connection to DNS Resolver addresses.

data_connection_checker

Description

Checks for an internet (data) connection, by opening a socket to a list addresses

The defaults of the plugin should be sufficient to reliably determine if the device is currently connected to the global network, e.i. has access to the Internet.

Note that you should not be using the current network status for deciding whether you can reliably make a network connection. Always guard your app code against timeouts and errors that might come from the network layer.

Quick start:

DataConnectionChecker() is actually a Singleton. Calling DataConnectionChecker() is guaranteed to always return the same instance.

You can supply a new list to DataConnectionChecker().addresses if you need to check different destinations, ports and timeouts. Also, each address can have its own port and timeout. See InternetAddressCheckOptions in the docs for more info.

bool result = await DataConnectionChecker().hasConnection;
if(result == true) {
  print('YAY! Free cute dog pics!');
} else {
  print('No internet :( Reason:');
  print(DataConnectionChecker().lastTryResults);
}

Purpose

The reason this package exists is that connectivity package cannot reliably determine if a data connection is actually available. More info on its page here: https://pub.dev/packages/connectivity

More info on the issue in general:

• https://stackoverflow.com/questions/1560788/how-to-check-internet-access-on-android-inetaddress-never-times-out/27312494#27312494 (this is the best approach so far IMO and it's what I'm using)

You can use this package in combination with connectivity in the following way:

var isDeviceConnected = false;

var subscription = Connectivity().onConnectivityChanged.listen((ConnectivityResult result) async {
  if(result != ConnectivityResult.none) {
    isDeviceConnected = await DataConnectionChecker().hasConnection;
  }
});

Note: remember to properly cancel the subscription when it's no longer needed. See connectivity package docs for more info.

How it works

All addresses are pinged simultaneously. On successful result (socket connection to address/port succeeds) a true boolean is pushed to a list, on failure (usually on timeout, default 10 sec) a false boolean is pushed to the same list.

When all the requests complete with either success or failure, a check is made to see if the list contains at least one true boolean. If it does, then an external address is available, so we have data connection. If all the values in this list are false, then we have no connection to the outside world of cute cat and dog pictures, so hasConnection also returns false too.

This all happens at the same time for all addresses, so the maximum waiting time is the address with the highest specified timeout, in case it's unreachable.

I believe this is a reliable and fast method to check if a data connection is available to a device, but I may be wrong. I suggest you open an issue on the Github repository page if you have a better way of.

Defaults

The defaults are based on data collected from https://perfops.net/ (https://www.dnsperf.com/#!dns-resolvers) Here's some more info about it:

DEFAULT_ADDRESSES includes the top 3 globally available DNS resolvers:

1.1.1.1           CloudFlare, info: https://one.one.one.one/ http://1.1.1.1
8.8.4.4           Google, info: https://developers.google.com/speed/public-dns/
208.67.220.220    OpenDNS, info: https://use.opendns.com/

static final List<AddressCheckOptions> DEFAULT_ADDRESSES = List.unmodifiable([
  AddressCheckOptions(
    InternetAddress('1.1.1.1'),
    port: DEFAULT_PORT,
    timeout: DEFAULT_TIMEOUT,
  ),
  AddressCheckOptions(
    InternetAddress('8.8.4.4'),
    port: DEFAULT_PORT,
    timeout: DEFAULT_TIMEOUT,
  ),
  AddressCheckOptions(
    InternetAddress('208.67.222.222'),
    port: DEFAULT_PORT,
    timeout: DEFAULT_TIMEOUT,
  ),
]);

DEFAULT_PORT is 53

A DNS server listens for requests on port 53 (both UDP and TCP). So all DNS requests are sent to port 53 ...

More info:

• https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
• https://www.google.com/search?q=dns+server+port

static const int DEFAULT_PORT = 53;

DEFAULT_TIMEOUT is 10 seconds

static const Duration DEFAULT_TIMEOUT = Duration(seconds: 10);

Usage

Example:

import 'package:data_connection_checker/data_connection_checker.dart';

main() async {
  print("The statement 'this machine is connected to the Internet' is: ");
  print(await DataConnectionChecker().hasConnection);

  // We can also get an enum instead of a bool
  print(await DataConnectionChecker().connectionStatus);
  // prints either DataConnectionStatus.connected
  // or DataConnectionStatus.disconnected

  print('Results from the last check:');
  print(DataConnectionChecker().lastTryResults);
}

See example folder for more examples.

License

MIT

Copyright 2019 Kristiyan Mitev

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Features and bugs

Please file feature requests and bugs at the issue tracker.