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Published: 08 Jan 09:08
I starred rwbutler/Connectivity at GitHub.
Makes Internet connectivity detection more robust by detecting Wi-Fi networks without Internet access.
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Connectivity

CI Status Version Carthage compatible Maintainability License Platform Swift 4.2 Reviewed by Hound

Connectivity is a wrapper for Apple's Reachability providing a reliable measure of whether Internet connectivity is available where Reachability alone can only indicate whether an interface is available that might allow a connection.

Connectivity's objective is to solve the captive portal problem whereby an iOS device is connected to a WiFi network lacking Internet connectivity. Such situations are commonplace and may occur for example when connecting to a public WiFi network which requires the user to register before use. Connectivity can detect such situations enabling you to react accordingly.

To learn more about how to use Connectivity, take a look at the keynote presentation, check out the blog post, or make use of the table of contents below:

Features

  • Detect captive portals when a device joins a network.
  • Detect when connected to a router that has no Internet access.
  • Be notified of changes in Internet connectivity.
  • Polling connectivity checks may be performed where a constant network connection is required (optional).

What's new in Connectivity 2.0.0?

Connectivity 2.0.0 provides the option of using the new Network framework on iOS 12 and above. To make use of this functionality set the framework property to .network as follows:

let connectivity = Connectivity()
connectivity.framework = .network

Below iOS 12, Connectivity will default to the traditional behaviour of using Reachability to determine the availability of network interfaces.

For more information, refer to CHANGELOG.md.

Installation

Ensure that you include Apple's Reachability header and implementation files (Reachability.h and Reachability.m) to use.

Use of Apple's Reachability is subject to licensing from Apple.

Cocoapods

CocoaPods is a dependency manager which integrates dependencies into your Xcode workspace. To install it using Ruby gems run:

gem install cocoapods

To install Connectivity using Cocoapods, simply add the following line to your Podfile:

pod "Connectivity"

Then run the command:

pod install

For more information see here.

Carthage

Carthage is a dependency manager which produces a binary for manual integration into your project. It can be installed via Homebrew using the commands:

brew update
brew install carthage

In order to integrate Connectivity into your project via Carthage, add the following line to your project's Cartfile:

github "rwbutler/Connectivity"

From the macOS Terminal run carthage update --platform iOS to build the framework then drag Connectivity.framework into your Xcode project.

For more information see here.

How It Works

iOS adopts a protocol called Wireless Internet Service Provider roaming (WISPr 2.0) published by the Wireless Broadband Alliance. This protocol defines the Smart Client to Access Gateway interface describing how to authenticate users accessing public IEEE 802.11 (Wi-Fi) networks using the Universal Access Method in which a captive portal presents a login page to the user.

The user must then register or provide login credentials via a web browser in order to be granted access to the network using RADIUS or another protocol providing centralized Authentication, Authorization, and Accounting (AAA).

In order to detect a that it has connected to a Wi-Fi network with a captive portal, iOS contacts a number of endpoints hosted by Apple - an example being https://www.apple.com/library/test/success.html. Each endpoint hosts a small HTML page of the form:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
	<TITLE>Success</TITLE>
</HEAD>
<BODY>
	Success
</BODY>
</HTML>

If on downloading this small HTML page iOS finds that it contains the word Success as above then it knows that Internet connectivity is available. However, if a login page is presented by a captive portal then the word Success will not be present and iOS will realize that the network connection has been hijacked by a captive portal and will present a browser window allowing the user to login or register.

Apple hosts a number of these pages such that should one of these pages go down, a number of fallbacks can be checked to determine whether connectivity is present or whether our connection is blocked by the presence of a captive portal. Unfortunately iOS exposes no framework to developers which allows us to make use of the operating system’s awareness of captive portals.

Connectivity is an open-source framework which wraps Reachability and endeavours to replicate iOS’s means of detecting captive portals. When Reachability detects Wi-Fi or WWAN connectivity, Connectivity contacts a number of endpoints to determine whether true Internet connectivity is present or whether a captive portal is intercepting the connections. This approach can also be used to determine whether an iOS device is connected to a Wi-Fi router with no Internet access.

Connectivity provides an interface as close to Reachability as possible so that it is familiar to developers used to working with Reachability. This includes providing the methods startNotifier() and stopNotifier() to begin checking for changes in Internet connectivity. Once the notifier has been started, you may query for the current connectivity status synchronously using the status property (similar to Reachability’s currentReachabilityStatus) or asynchronously by registering as an observer with the default NotificationCenter for the notification kNetworkConnectivityChangedNotification (in Swift this is accessed through Notification.Name.ConnectivityDidChange) — similar to Reachability’s notification kNetworkReachabilityChangedNotification.

By default, Connectivity contacts a number of endpoints already used by iOS but it recommended that these are supplemented by endpoints hosted by the developer by appending to the connectivityURLs property. Further customization is possible through setting the successThreshold property which determines the percentage of endpoints contacted which must result in a successful check in order to conclude that connectivity is present. The default value specifies that 75% of URLs contacted must result in a successful connectivity check.

Usage

For an example of how to use Connectivity, see the sample app in the Example directory.

Callbacks

To get started using Connectivity, simply instantiate an instance and assign a closure to be invoked when Connectivity detects that you are connected to the Internet, when disconnected, or in both cases as follows:

let connectivity: Connectivity = Connectivity()

let connectivityChanged: (Connectivity) -> Void = { [weak self] connectivity in
     self?.updateConnectionStatus(connectivity.status)
}

connectivity.whenConnected = connectivityChanged
connectivity.whenDisconnected = connectivityChanged

func updateConnectionStatus(_ status: Connectivity.ConnectivityStatus) {

    switch status {
      case .connected:
	    case .connectedViaWiFi:
	    case .connectedViaWiFiWithoutInternet:
	    case .connectedViaWWAN:
	    case .connectedViaWWANWithoutInternet:
	    case .notConnected:
    }
        
}

Then to start listening for changes in Connectivity call:

connectivity.startNotifier()

Then remember to call connectivity.stopNotifier() when you are done.

One-Off Checks

Sometimes you only want to check the connectivity state as a one-off. To do so, instantiate a Connectivity object then check the status property as follows:

let connectivity = Connectivity()

connectivity.checkConnectivity { connectivity in

	switch connectivity.status {
		case .connected: 
			break
		case .connectedViaWiFi:
			break
		case .connectedViaWiFiWithoutInternet:
			break
		case .connectedViaWWAN:
			break
		case .connectedViaWWANWithoutInternet:
			break
		case .notConnected:
			break
	}

}

Alternatively, you may check the following properties of the Connectivity object directly if you are only interested in certain types of connections:

var isConnectedViaCellular: Bool

var isConnectedViaWiFi: Bool
    
var isConnectedViaCellularWithoutInternet: Bool

var isConnectedViaWiFiWithoutInternet: Bool

Connectivity URLs

It is possible to set the URLs which will be contacted to check connectivity via the connectivityURLs property of the Connectivity object before starting connectivity checks with startNotifier().

connectivity.connectivityURLs = [URL(string: "https://www.apple.com/library/test/success.html")!]

Notifications

If you prefer using notifications to observe changes in connectivity, you may add an observer on the default NotificationCenter:

NotificationCenter.default.addObserver(_:selector:name:object:)

Listening for Notification.Name.ConnectivityDidChange, the object property of received notifications will contain the Connectivity object which you can use to query connectivity status.

Polling

In certain cases you may need to be kept constantly apprised of changes in connectivity state and therefore may wish to enable polling. Where enabled, Connectivity will not wait on changes in Reachability state but will poll the connectivity URLs every 10 seconds (this value is configurable). ConnectivityDidChange notifications and the closures assigned to the whenConnected and whenDisconnected properties will be invoked only where changes in connectivity state occur.

To enable polling:

connectivity.isPollingEnabled = true
connectivity.startNotifier()

As always, remember to call stopNotifier() when you are done.

SSL

As of Connectivity 1.1.0, using HTTPS for connectivity URLs is the default setting. If your app doesn't make use of App Transport Security and you wish to make use of HTTP URLs as well as HTTPS ones then either set isHTTPSOnly to false or set shouldUseHTTPS to false when instantiating the Connectivity object as follows*:

let connectivity = Connectivity(shouldUseHTTPS: false)

*Note that the property will not be set if you have not set the NSAllowsArbitraryLoads flag in your app's Info.plist first.

Threshold

To set the number of successful connections required in order to be deemed successfully connected, set the successThreshold property. The value is specified as a percentage indicating the percentage of successful connections i.e. if four connectivity URLs are set in the connectivityURLs property and a threshold of 75% is specified then three out of the four checks must succeed in order for our app to be deemed connected:

connectivity.successThreshold = Connectivity.Percentage(75.0)

Response Validation

There are three different validation modes available for checking response content these being:

  • .containsExpectedResponseString - Checks that the response contains the expected response as defined by the expectedResponseString property.
  • .equalsExpectedResponseString - Checks that the response equals the expected response as defined by the expectedResponseString property.
  • .matchesRegularExpression - Checks that the response matches the regular expression as defined by the expectedResponseRegEx property.

Author

Ross Butler

License

Connectivity is available under the MIT license. See the LICENSE file for more info.

Additional Software

Controls

AnimatedGradientView
AnimatedGradientView

Frameworks

  • Cheats - Retro cheat codes for modern iOS apps.
  • Connectivity - Improves on Reachability for determining Internet connectivity in your iOS application.
  • FeatureFlags - Allows developers to configure feature flags, run multiple A/B or MVT tests using a bundled / remotely-hosted JSON configuration file.
  • Skylark - Fully Swift BDD testing framework for writing Cucumber scenarios using Gherkin syntax.
  • TailorSwift - A collection of useful Swift Core Library / Foundation framework extensions.
  • TypographyKit - Consistent & accessible visual styling on iOS with Dynamic Type support.
  • Updates - Automatically detects app updates and gently prompts users to update.
Cheats Connectivity FeatureFlags Skylark TypographyKit Updates
Cheats Connectivity FeatureFlags Skylark TypographyKit Updates

Tools

  • Config Validator - Config Validator validates & uploads your configuration files and cache clears your CDN as part of your CI process.
  • IPA Uploader - Uploads your apps to TestFlight & App Store.
  • Palette - Makes your TypographyKit color palette available in Xcode Interface Builder.
Config Validator IPA Uploader Palette
Config Validator IPA Uploader Palette