iosswiftconnectionreachabilityreachability-swift

Swift iOS -AshleyMills Reachability keeps toggling wifi on and off every few secs

I downloaded the iOS sample Reachability project from AshleyMills Reachability

It has a networkStatus label that says either: Wifi or No Connection

Underneath that it has a hostNameLabel that says either: No host name or google.com or invalidhost

When I run the app on my device it repeatedly cycles the connection every 5 seconds in the following manner:

1st 5 secs:

enter image description here

2nd 5 sec:

enter image description here

3rd 5 secs:

enter image description here

Start cycle over from 1st, 2nd, and 3rd all over again and keep repeating.

I'm on Home wifi and my internet connection is strong (no problems with any other apps). Why does it continuously cycle like this instead of just staying on Wifi + google.com (the 2nd cycle)

ViewController File:

class ViewController: UIViewController {

    let networkStatus: UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont.systemFont(ofSize: 21)
        label.textColor = .black
        label.numberOfLines = 0
        label.sizeToFit()
        label.text = "Status"
        label.textAlignment = .center
        return label
    }()

    let hostNameLabel: UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont.systemFont(ofSize: 21)
        label.textColor = .black
        label.numberOfLines = 0
        label.sizeToFit()
        label.text = "Host"
        label.textAlignment = .center
        return label
    }()

    var reachability: Reachability?
    let hostNames = [nil, "google.com", "invalidhost"]
    var hostIndex = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        setConstraints()
        startHost(at: 0)
    }

    func startHost(at index: Int) {
        stopNotifier()
        setupReachability(hostNames[index], useClosures: true)
        startNotifier()
        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
            self.startHost(at: (index + 1) % 3)
        }
    }

    func setupReachability(_ hostName: String?, useClosures: Bool) {
        let reachability: Reachability?
        if let hostName = hostName {
            reachability = Reachability(hostname: hostName)
            hostNameLabel.text = hostName
        } else {
            reachability = Reachability()
            hostNameLabel.text = "No host name"
        }
        self.reachability = reachability
        print("--- set up with host name: \(hostNameLabel.text!)")

        if useClosures {
            reachability?.whenReachable = { reachability in
                self.updateLabelColourWhenReachable(reachability)
            }
            reachability?.whenUnreachable = { reachability in
                self.updateLabelColourWhenNotReachable(reachability)
            }
        } else {
            NotificationCenter.default.addObserver(
                self,
                selector: #selector(reachabilityChanged(_:)),
                name: .reachabilityChanged,
                object: reachability
            )
        }
    }

    func startNotifier() {
        print("--- start notifier")
        do {
            try reachability?.startNotifier()
        } catch {
            networkStatus.textColor = .red
            networkStatus.text = "Unable to start\nnotifier"
            return
        }
    }

    func stopNotifier() {
        print("--- stop notifier")
        reachability?.stopNotifier()
        NotificationCenter.default.removeObserver(self, name: .reachabilityChanged, object: nil)
        reachability = nil
    }

    func updateLabelColourWhenReachable(_ reachability: Reachability) {
        print("\(reachability.description) - \(reachability.connection)")
        if reachability.connection == .wifi {
            self.networkStatus.textColor = .green
        } else {
            self.networkStatus.textColor = .blue
        }

        self.networkStatus.text = "\(reachability.connection)"
    }

    func updateLabelColourWhenNotReachable(_ reachability: Reachability) {
        print("\(reachability.description) - \(reachability.connection)")

        self.networkStatus.textColor = .red

        self.networkStatus.text = "\(reachability.connection)"
    }

    @objc func reachabilityChanged(_ note: Notification) {
        let reachability = note.object as! Reachability

        if reachability.connection != .none {
            updateLabelColourWhenReachable(reachability)
        } else {
            updateLabelColourWhenNotReachable(reachability)
        }
    }

    func setConstraints(){
        view.addSubview(networkStatus)
        view.addSubview(hostNameLabel)

        networkStatus.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 8).isActive = true
        networkStatus.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -8).isActive = true
        networkStatus.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        hostNameLabel.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 8).isActive = true
        hostNameLabel.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -8).isActive = true
        hostNameLabel.topAnchor.constraint(equalTo: networkStatus.bottomAnchor, constant: 20).isActive = true
    }

    deinit {
        stopNotifier()
    }
}

Reachability File:

import SystemConfiguration
import Foundation

public enum ReachabilityError: Error {
    case FailedToCreateWithAddress(sockaddr_in)
    case FailedToCreateWithHostname(String)
    case UnableToSetCallback
    case UnableToSetDispatchQueue
}

@available(*, unavailable, renamed: "Notification.Name.reachabilityChanged")
public let ReachabilityChangedNotification = NSNotification.Name("ReachabilityChangedNotification")

extension Notification.Name {
    public static let reachabilityChanged = Notification.Name("reachabilityChanged")
}

func callback(reachability: SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
    guard let info = info else { return }

    let reachability = Unmanaged<Reachability>.fromOpaque(info).takeUnretainedValue()
    reachability.reachabilityChanged()
}

public class Reachability {

    public typealias NetworkReachable = (Reachability) -> ()
    public typealias NetworkUnreachable = (Reachability) -> ()

    @available(*, unavailable, renamed: "Connection")
    public enum NetworkStatus: CustomStringConvertible {
        case notReachable, reachableViaWiFi, reachableViaWWAN
        public var description: String {
            switch self {
            case .reachableViaWWAN: return "Cellular"
            case .reachableViaWiFi: return "WiFi"
            case .notReachable: return "No Connection"
            }
        }
    }

    public enum Connection: CustomStringConvertible {
        case none, wifi, cellular
        public var description: String {
            switch self {
            case .cellular: return "Cellular"
            case .wifi: return "WiFi"
            case .none: return "No Connection"
            }
        }
    }

    public var whenReachable: NetworkReachable?
    public var whenUnreachable: NetworkUnreachable?

    @available(*, deprecated: 4.0, renamed: "allowsCellularConnection")
    public let reachableOnWWAN: Bool = true

    /// Set to `false` to force Reachability.connection to .none when on cellular connection (default value `true`)
    public var allowsCellularConnection: Bool

    // The notification center on which "reachability changed" events are being posted
    public var notificationCenter: NotificationCenter = NotificationCenter.default

    @available(*, deprecated: 4.0, renamed: "connection.description")
    public var currentReachabilityString: String {
        return "\(connection)"
    }

    @available(*, unavailable, renamed: "connection")
    public var currentReachabilityStatus: Connection {
        return connection
    }

    public var connection: Connection {
        guard isReachableFlagSet else { return .none }

        // If we're reachable, but not on an iOS device (i.e. simulator), we must be on WiFi
        guard isRunningOnDevice else { return .wifi }

        var connection = Connection.none

        if !isConnectionRequiredFlagSet {
            connection = .wifi
        }

        if isConnectionOnTrafficOrDemandFlagSet {
            if !isInterventionRequiredFlagSet {
                connection = .wifi
            }
        }

        if isOnWWANFlagSet {
            if !allowsCellularConnection {
                connection = .none
            } else {
                connection = .cellular
            }
        }

        return connection
    }

    fileprivate var previousFlags: SCNetworkReachabilityFlags?

    fileprivate var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
        return false
        #else
        return true
        #endif
    }()

    fileprivate var notifierRunning = false
    fileprivate let reachabilityRef: SCNetworkReachability

    fileprivate let reachabilitySerialQueue = DispatchQueue(label: "uk.co.ashleymills.reachability")

    fileprivate var usingHostname = false

    required public init(reachabilityRef: SCNetworkReachability, usingHostname: Bool = false) {
        allowsCellularConnection = true
        self.reachabilityRef = reachabilityRef
        self.usingHostname = usingHostname
    }

    public convenience init?(hostname: String) {
        guard let ref = SCNetworkReachabilityCreateWithName(nil, hostname) else { return nil }
        self.init(reachabilityRef: ref, usingHostname: true)
    }

    public convenience init?() {
        var zeroAddress = sockaddr()
        zeroAddress.sa_len = UInt8(MemoryLayout<sockaddr>.size)
        zeroAddress.sa_family = sa_family_t(AF_INET)

        guard let ref = SCNetworkReachabilityCreateWithAddress(nil, &zeroAddress) else { return nil }

        self.init(reachabilityRef: ref)
    }

    deinit {
        stopNotifier()
    }
}

public extension Reachability {

    // MARK: - *** Notifier methods ***
    func startNotifier() throws {
        guard !notifierRunning else { return }

        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = UnsafeMutableRawPointer(Unmanaged<Reachability>.passUnretained(self).toOpaque())
        if !SCNetworkReachabilitySetCallback(reachabilityRef, callback, &context) {
            stopNotifier()
            throw ReachabilityError.UnableToSetCallback
        }

        if !SCNetworkReachabilitySetDispatchQueue(reachabilityRef, reachabilitySerialQueue) {
            stopNotifier()
            throw ReachabilityError.UnableToSetDispatchQueue
        }

        // Perform an initial check
        reachabilitySerialQueue.async {
            self.reachabilityChanged()
        }

        notifierRunning = true
    }

    func stopNotifier() {
        defer { notifierRunning = false }

        SCNetworkReachabilitySetCallback(reachabilityRef, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachabilityRef, nil)
    }

    // MARK: - *** Connection test methods ***
    @available(*, deprecated: 4.0, message: "Please use `connection != .none`")
    var isReachable: Bool {
        guard isReachableFlagSet else { return false }

        if isConnectionRequiredAndTransientFlagSet {
            return false
        }

        if isRunningOnDevice {
            if isOnWWANFlagSet && !reachableOnWWAN {
                // We don't want to connect when on cellular connection
                return false
            }
        }

        return true
    }

    @available(*, deprecated: 4.0, message: "Please use `connection == .cellular`")
    var isReachableViaWWAN: Bool {
        // Check we're not on the simulator, we're REACHABLE and check we're on WWAN
        return isRunningOnDevice && isReachableFlagSet && isOnWWANFlagSet
    }

    @available(*, deprecated: 4.0, message: "Please use `connection == .wifi`")
    var isReachableViaWiFi: Bool {
        // Check we're reachable
        guard isReachableFlagSet else { return false }

        // If reachable we're reachable, but not on an iOS device (i.e. simulator), we must be on WiFi
        guard isRunningOnDevice else { return true }

        // Check we're NOT on WWAN
        return !isOnWWANFlagSet
    }

    var description: String {
        let W = isRunningOnDevice ? (isOnWWANFlagSet ? "W" : "-") : "X"
        let R = isReachableFlagSet ? "R" : "-"
        let c = isConnectionRequiredFlagSet ? "c" : "-"
        let t = isTransientConnectionFlagSet ? "t" : "-"
        let i = isInterventionRequiredFlagSet ? "i" : "-"
        let C = isConnectionOnTrafficFlagSet ? "C" : "-"
        let D = isConnectionOnDemandFlagSet ? "D" : "-"
        let l = isLocalAddressFlagSet ? "l" : "-"
        let d = isDirectFlagSet ? "d" : "-"

        return "\(W)\(R) \(c)\(t)\(i)\(C)\(D)\(l)\(d)"
    }
}

fileprivate extension Reachability {
    func reachabilityChanged() {
        guard previousFlags != flags else { return }

        let block = connection != .none ? whenReachable : whenUnreachable

        DispatchQueue.main.async {
            if self.usingHostname {
                print("USING HOSTNAME ABOUT TO CALL BLOCK")
            }
            block?(self)
            self.notificationCenter.post(name: .reachabilityChanged, object:self)
        }

        previousFlags = flags
    }

    var isOnWWANFlagSet: Bool {
        #if os(iOS)
        return flags.contains(.isWWAN)
        #else
        return false
        #endif
    }
    var isReachableFlagSet: Bool {
        return flags.contains(.reachable)
    }
    var isConnectionRequiredFlagSet: Bool {
        return flags.contains(.connectionRequired)
    }
    var isInterventionRequiredFlagSet: Bool {
        return flags.contains(.interventionRequired)
    }
    var isConnectionOnTrafficFlagSet: Bool {
        return flags.contains(.connectionOnTraffic)
    }
    var isConnectionOnDemandFlagSet: Bool {
        return flags.contains(.connectionOnDemand)
    }
    var isConnectionOnTrafficOrDemandFlagSet: Bool {
        return !flags.intersection([.connectionOnTraffic, .connectionOnDemand]).isEmpty
    }
    var isTransientConnectionFlagSet: Bool {
        return flags.contains(.transientConnection)
    }
    var isLocalAddressFlagSet: Bool {
        return flags.contains(.isLocalAddress)
    }
    var isDirectFlagSet: Bool {
        return flags.contains(.isDirect)
    }
    var isConnectionRequiredAndTransientFlagSet: Bool {
        return flags.intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]
    }

    var flags: SCNetworkReachabilityFlags {
        var flags = SCNetworkReachabilityFlags()
        if SCNetworkReachabilityGetFlags(reachabilityRef, &flags) {
            print("Returning flags \(flags)")
            return flags
        } else {
            return SCNetworkReachabilityFlags()
        }
    }
}
Solution

  • I looked through the code and found the answer. Inside the ViewController file the startHost() function has timer in it that cycles every 5 secs.

    func startHost(at index: Int) {
        stopNotifier()
        setupReachability(hostNames[index], useClosures: true)
        startNotifier()

        // Timer is HERE
        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
            self.startHost(at: (index + 1) % 3)
        }
    }