How to know whether actual internet is available or not in Swift?

Question

I want to get notified when my WiFi Router color changes from Green to Red

I am making an app which will tell you whether you are online or offline from menu bar in Swift which is open source & can be found at https://github.com/deadcoder0904/net-alert

I want to know if its possible to get notified when WiFi color changes in Swift.

I can't constantly ping my server to know that the color changed as this would be wasting internet resources.

So is it possible to know this in Swift?

Answer 1

First of all, I'm going to answer this from iOS perspective. But your GitHub demo is for macOS. I think the basics are the same.

I'll go to solve this in protocol oriented approach.

---

Update:

After quite a lot of searching I've come across the magnificent implementation of Connectivity wrapper. There is even a descriptive blogpost Solving the Captive Portal Problem on iOS if you want to know more about it. This implementation is capable of dealing with actual internet available / not-available states.

Note: Don't like to read further? Here is the working version that I'm going to illustrate briefly. Navigation bar will reflect with Green & Red color for different connection status.

Define a protocol:

This protocol will help any interested object to be notified when any change in connectivity occurs.

protocol ConnectivityNotifiable {
    var connectivity: Connectivity { get }
    func startNotifyingConnectivityChangeStatus()
    func stopNotifyingConnectivityChangeStatus()
    func connectivityChanged(toStatus: ConnectivityStatus)
}

// Provide some default implementation through protocol extension
extension ConnectivityNotifiable {
    func startNotifyingConnectivityChangeStatus() {
        connectivity.isPollingEnabled = true
        connectivity.startNotifier()
        connectivity.whenConnected = { connectivity in
            self.connectivityChanged(toStatus: connectivity.status)
        }
        connectivity.whenDisconnected = { connectivity in
            self.connectivityChanged(toStatus: connectivity.status)
        }
    }
    func stopNotifyingConnectivityChangeStatus() {
        connectivity.stopNotifier()
    }
}

Conform to the protocol:

Conforming to the ConnectivityNotifiable protocol will add the functionality to any interested object to be notified when Connectivity status changes. Something like monitoring.

class ViewController: UIViewController, ConnectivityNotifiable {

    // ConnectivityNotifiable protocol requirement
    let connectivity = Connectivity()

    override func viewDidLoad() {
        super.viewDidLoad()

        // Invoke the default implementation of the ConnectivityNotifiable protocol
        // requirement to be able to be notified
        startNotifyingConnectivityChangeStatus()

        // Reminder:
        // Don't forget to invoke stopNotifyingConnectivityChangeStatus() when
        // you are done or when the lifecycle of your controller ends
    }

    // ConnectivityNotifiable protocol requirement
    func connectivityChanged(toStatus: ConnectivityStatus) {
        // Everytime any change happens in the network connectivity 
        // this method will be invoked with appropriate connection status
        switch toStatus {

        case .connected, 
             .connectedViaWiFi, 
             .connectedViaCellular:
            // Connected/Internet available. Update any UI component

        case .notConnected, 
             .connectedViaWiFiWithoutInternet, 
             .connectedViaCellularWithoutInternet:
            // Disconnected/Internet not available. Update any UI component
        }
    }
}

---

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Old Answer

Note: If you are using the latest release of the Reachability, you won't need the NotificationCenter based solution to get reachability change notification. It works completely fine with closure based approach.

---

Don't like to know how to achieve this? Here is a working version made for iOS platform. Clone the repo and check yourself. Navigation bar will reflect with Green, Orange & Red color for different connection status.

Define a protocol:

This protocol will help any interested object to be notified when any change in reachability occurs.

protocol Reachable {
    var reachability: Reachability { get }
    func startMonitoringReachabilityChangeStatus()
    func reachabilityChanged(to: Reachability.Connection)
}

extension Reachable {
    func startMonitoringReachabilityChangeStatus() {
        do {
            try reachability.startNotifier()
        } catch {
            print(error.localizedDescription)
        }
        reachability.whenReachable = { reachability in
            self.reachabilityChanged(to: reachability.connection)
        }
        reachability.whenUnreachable = { reachability in
            self.reachabilityChanged(to: reachability.connection)
        }
    }
}

Conform to the protocol:

Conforming to the Reachable protocol will add the functionality to any interested object to be notified when reachability status changes. Something like monitoring.

class ViewController: UIViewController, Reachable {

    // Reachable protocol requirement
    let reachability: Reachability = Reachability()!

    override func viewDidLoad() {
        super.viewDidLoad()

        // initial reachability checkup
        reachabilityChanged(to: reachability.connection)

        // Invoke the default implementation of the Reachable protocol requirement 
        // to be able to be notified
        startMonitoringReachabilityChangeStatus()
    }

    // Reachable protocol requirement
    func reachabilityChanged(to: Reachability.Connection) {
        // Everytime any change happens in the network connectivity 
        // this method will be invoked with appropriate connection status
        switch to {
        case .wifi:
            DispatchQueue.main.async {
                // Update any UI component
            }
        case .cellular:
            DispatchQueue.main.async {
                // Update any UI component
            }
        case .none:
            DispatchQueue.main.async {
                // Update any UI component
            }
        }
    }
}