Using Apple's Reachability to Check Remote Server Reachability in Swift

Using Apple's Reachability to check remote server reachability in Swift

The Reachability class you're using is based on Apple's SCNetworkReachability class, which doesn't do exactly what you're hoping. From the SCNetworkReachability documentation:

A remote host is considered reachable when a data packet, sent by an
application into the network stack, can leave the local device.
Reachability does not guarantee that the data packet will actually be
received by the host.

So it's not built for testing whether or not the remote host is actually online, just whether (1) the current network settings will allow an attempt to reach it and (2) by what methods. Once you've determined that the network is active you'll need to make an attempt to connect to see if the remote host is actually up and running.

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Note: This test:

(ReachabilityInst.currentReachabilityStatus().value == ReachableViaWiFi.value)

is the correct way to check -- for some reason NetworkStatus is one of the few Apple enumerations created without the NS_ENUM macro.

Using Apple's reachability class in Swift

For network availability (works in Swift 2):

class func hasConnectivity() -> Bool {
    let reachability: Reachability = Reachability.reachabilityForInternetConnection()
    let networkStatus: Int = reachability.currentReachabilityStatus().rawValue
    return networkStatus != 0
}

For a Wi-Fi connection:

(reachability.currentReachabilityStatus().value == ReachableViaWiFi.value)

Using Reachability Class in Swift

Personally I would recommend you to use tonymillion's alternative to Reachability class, which can be found here:

https://github.com/tonymillion/Reachability

Then you can determine the connection in 1 line:

let connected: Bool = Reachability.reachabilityForInternetConnection().isReachable()

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I would also recommend you to install this through CocoaPods if you have never tried that before. The reason being that Google will distribute all of their future iOS SDKs through CocoaPods, so you might start getting some practice with it already now :)

Check for internet connection with Swift

To solve the 4G issue mentioned in the comments I have used @AshleyMills reachability implementation as a reference and rewritten Reachability for Swift 3.1:

updated: Xcode 10.1 • Swift 4 or later

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Reachability.swift file

import Foundation
import SystemConfiguration

class Reachability {
    var hostname: String?
    var isRunning = false
    var isReachableOnWWAN: Bool
    var reachability: SCNetworkReachability?
    var reachabilityFlags = SCNetworkReachabilityFlags()
    let reachabilitySerialQueue = DispatchQueue(label: "ReachabilityQueue")
    init(hostname: String) throws {
        guard let reachability = SCNetworkReachabilityCreateWithName(nil, hostname) else {
            throw Network.Error.failedToCreateWith(hostname)
        }
        self.reachability = reachability
        self.hostname = hostname
        isReachableOnWWAN = true
        try start()
    }
    init() throws {
        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
        zeroAddress.sin_family = sa_family_t(AF_INET)
        guard let reachability = withUnsafePointer(to: &zeroAddress, {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                SCNetworkReachabilityCreateWithAddress(nil, $0)
            }
        }) else {
            throw Network.Error.failedToInitializeWith(zeroAddress)
        }
        self.reachability = reachability
        isReachableOnWWAN = true
        try start()
    }
    var status: Network.Status {
        return  !isConnectedToNetwork ? .unreachable :
                isReachableViaWiFi    ? .wifi :
                isRunningOnDevice     ? .wwan : .unreachable
    }
    var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
            return false
        #else
            return true
        #endif
    }()
    deinit { stop() }
}

---

extension Reachability {

    func start() throws {
        guard let reachability = reachability, !isRunning else { return }
        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = Unmanaged<Reachability>.passUnretained(self).toOpaque()
        guard SCNetworkReachabilitySetCallback(reachability, callout, &context) else { stop()
            throw Network.Error.failedToSetCallout
        }
        guard SCNetworkReachabilitySetDispatchQueue(reachability, reachabilitySerialQueue) else { stop()
            throw Network.Error.failedToSetDispatchQueue
        }
        reachabilitySerialQueue.async { self.flagsChanged() }
        isRunning = true
    }

    func stop() {
        defer { isRunning = false }
        guard let reachability = reachability else { return }
        SCNetworkReachabilitySetCallback(reachability, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachability, nil)
        self.reachability = nil
    }

    var isConnectedToNetwork: Bool {
        return isReachable &&
               !isConnectionRequiredAndTransientConnection &&
               !(isRunningOnDevice && isWWAN && !isReachableOnWWAN)
    }

    var isReachableViaWiFi: Bool {
        return isReachable && isRunningOnDevice && !isWWAN
    }

    /// Flags that indicate the reachability of a network node name or address, including whether a connection is required, and whether some user intervention might be required when establishing a connection.
    var flags: SCNetworkReachabilityFlags? {
        guard let reachability = reachability else { return nil }
        var flags = SCNetworkReachabilityFlags()
        return withUnsafeMutablePointer(to: &flags) {
            SCNetworkReachabilityGetFlags(reachability, UnsafeMutablePointer($0))
            } ? flags : nil
    }

    /// compares the current flags with the previous flags and if changed posts a flagsChanged notification
    func flagsChanged() {
        guard let flags = flags, flags != reachabilityFlags else { return }
        reachabilityFlags = flags
        NotificationCenter.default.post(name: .flagsChanged, object: self)
    }

    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var transientConnection: Bool { return flags?.contains(.transientConnection) == true }

    /// The specified node name or address can be reached using the current network configuration.
    var isReachable: Bool { return flags?.contains(.reachable) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set, the kSCNetworkReachabilityFlagsConnectionOnTraffic flag, kSCNetworkReachabilityFlagsConnectionOnDemand flag, or kSCNetworkReachabilityFlagsIsWWAN flag is also typically set to indicate the type of connection required. If the user must manually make the connection, the kSCNetworkReachabilityFlagsInterventionRequired flag is also set.
    var connectionRequired: Bool { return flags?.contains(.connectionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. Any traffic directed to the specified name or address will initiate the connection.
    var connectionOnTraffic: Bool { return flags?.contains(.connectionOnTraffic) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established.
    var interventionRequired: Bool { return flags?.contains(.interventionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. The connection will be established "On Demand" by the CFSocketStream programming interface (see CFStream Socket Additions for information on this). Other functions will not establish the connection.
    var connectionOnDemand: Bool { return flags?.contains(.connectionOnDemand) == true }

    /// The specified node name or address is one that is associated with a network interface on the current system.
    var isLocalAddress: Bool { return flags?.contains(.isLocalAddress) == true }

    /// Network traffic to the specified node name or address will not go through a gateway, but is routed directly to one of the interfaces in the system.
    var isDirect: Bool { return flags?.contains(.isDirect) == true }

    /// The specified node name or address can be reached via a cellular connection, such as EDGE or GPRS.
    var isWWAN: Bool { return flags?.contains(.isWWAN) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set
    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var isConnectionRequiredAndTransientConnection: Bool {
        return (flags?.intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]) == true
    }
}

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func callout(reachability: SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
    guard let info = info else { return }
    DispatchQueue.main.async {
        Unmanaged<Reachability>
            .fromOpaque(info)
            .takeUnretainedValue()
            .flagsChanged()
    }
}

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extension Notification.Name {
    static let flagsChanged = Notification.Name("FlagsChanged")
}

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struct Network {
    static var reachability: Reachability!
    enum Status: String {
        case unreachable, wifi, wwan
    }
    enum Error: Swift.Error {
        case failedToSetCallout
        case failedToSetDispatchQueue
        case failedToCreateWith(String)
        case failedToInitializeWith(sockaddr_in)
    }
}

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Usage

Initialize it in your AppDelegate.swift didFinishLaunchingWithOptions method and handle any errors that might occur:

import UIKit
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        do {
            try Network.reachability = Reachability(hostname: "www.google.com")
        }
        catch {
            switch error as? Network.Error {
            case let .failedToCreateWith(hostname)?:
                print("Network error:\nFailed to create reachability object With host named:", hostname)
            case let .failedToInitializeWith(address)?:
                print("Network error:\nFailed to initialize reachability object With address:", address)
            case .failedToSetCallout?:
                print("Network error:\nFailed to set callout")
            case .failedToSetDispatchQueue?:
                print("Network error:\nFailed to set DispatchQueue")
            case .none:
                print(error)
            }
        }
        return true
    }
}

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And a view controller sample:

import UIKit
class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default
            .addObserver(self,
                         selector: #selector(statusManager),
                         name: .flagsChanged,
                         object: nil)
        updateUserInterface()
    }
    func updateUserInterface() {
        switch Network.reachability.status {
        case .unreachable:
            view.backgroundColor = .red
        case .wwan:
            view.backgroundColor = .yellow
        case .wifi:
            view.backgroundColor = .green
        }
        print("Reachability Summary")
        print("Status:", Network.reachability.status)
        print("HostName:", Network.reachability.hostname ?? "nil")
        print("Reachable:", Network.reachability.isReachable)
        print("Wifi:", Network.reachability.isReachableViaWiFi)
    }
    @objc func statusManager(_ notification: Notification) {
        updateUserInterface()
    }
}

Sample Project

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