ios-samples/ReachabilitySample/reachability.cs

using System;
using System.Net;
using SystemConfiguration;
using CoreFoundation;

public enum NetworkStatus
{
    NotReachable,
    ReachableViaCarrierDataNetwork,
    ReachableViaWiFiNetwork
}

public static class Reachability
{
    public static string HostName = "www.google.com";

    public static bool IsReachableWithoutRequiringConnection(NetworkReachabilityFlags flags)
    {
        // Is it reachable with the current network configuration?
        bool isReachable = (flags & NetworkReachabilityFlags.Reachable) != 0;

        // Do we need a connection to reach it?
        bool noConnectionRequired = (flags & NetworkReachabilityFlags.ConnectionRequired) == 0;

        // Since the network stack will automatically try to get the WAN up,
        // probe that
        if ((flags & NetworkReachabilityFlags.IsWWAN) != 0)
            noConnectionRequired = true;

        return isReachable && noConnectionRequired;
    }

    // Is the host reachable with the current network configuration
    public static bool IsHostReachable(string host)
    {
        if (string.IsNullOrEmpty(host))
            return false;

        using (var r = new NetworkReachability(host))
        {
            NetworkReachabilityFlags flags;

            if (r.TryGetFlags(out flags))
            {
                return IsReachableWithoutRequiringConnection(flags);
            }
        }
        return false;
    }

    //
    // Raised every time there is an interesting reachable event,
    // we do not even pass the info as to what changed, and
    // we lump all three status we probe into one
    //
    public static event EventHandler ReachabilityChanged;

    static void OnChange(NetworkReachabilityFlags flags)
    {
        var h = ReachabilityChanged;
        if (h != null)
            h(null, EventArgs.Empty);
    }

    //
    // Returns true if it is possible to reach the AdHoc WiFi network
    // and optionally provides extra network reachability flags as the
    // out parameter
    //
    static NetworkReachability adHocWiFiNetworkReachability;

    public static bool IsAdHocWiFiNetworkAvailable(out NetworkReachabilityFlags flags)
    {
        if (adHocWiFiNetworkReachability == null)
        {
            adHocWiFiNetworkReachability = new NetworkReachability(new IPAddress(new byte [] { 169, 254, 0, 0 }));
            adHocWiFiNetworkReachability.SetNotification(OnChange);
            adHocWiFiNetworkReachability.Schedule(CFRunLoop.Current, CFRunLoop.ModeDefault);
        }

        return adHocWiFiNetworkReachability.TryGetFlags(out flags) && IsReachableWithoutRequiringConnection(flags);
    }

    static NetworkReachability defaultRouteReachability;

    static bool IsNetworkAvailable(out NetworkReachabilityFlags flags)
    {
        if (defaultRouteReachability == null)
        {
            defaultRouteReachability = new NetworkReachability(new IPAddress(0));
            defaultRouteReachability.SetNotification(OnChange);
            defaultRouteReachability.Schedule(CFRunLoop.Current, CFRunLoop.ModeDefault);
        }
        return defaultRouteReachability.TryGetFlags(out flags) && IsReachableWithoutRequiringConnection(flags);
    }

    static NetworkReachability remoteHostReachability;

    public static NetworkStatus RemoteHostStatus()
    {
        NetworkReachabilityFlags flags;
        bool reachable;

        if (remoteHostReachability == null)
        {
            remoteHostReachability = new NetworkReachability(HostName);

            // Need to probe before we queue, or we wont get any meaningful values
            // this only happens when you create NetworkReachability from a hostname
            reachable = remoteHostReachability.TryGetFlags(out flags);

            remoteHostReachability.SetNotification(OnChange);
            remoteHostReachability.Schedule(CFRunLoop.Current, CFRunLoop.ModeDefault);
        }
        else
            reachable = remoteHostReachability.TryGetFlags(out flags);

        if (!reachable)
            return NetworkStatus.NotReachable;

        if (!IsReachableWithoutRequiringConnection(flags))
            return NetworkStatus.NotReachable;

        if ((flags & NetworkReachabilityFlags.IsWWAN) != 0)
            return NetworkStatus.ReachableViaCarrierDataNetwork;

        return NetworkStatus.ReachableViaWiFiNetwork;
    }

    public static NetworkStatus InternetConnectionStatus()
    {
        NetworkReachabilityFlags flags;
        bool defaultNetworkAvailable = IsNetworkAvailable(out flags);
        if (defaultNetworkAvailable && ((flags & NetworkReachabilityFlags.IsDirect) != 0))
        {
            return NetworkStatus.NotReachable;
        }
        else if ((flags & NetworkReachabilityFlags.IsWWAN) != 0)
            return NetworkStatus.ReachableViaCarrierDataNetwork;
        else if (flags == 0)
            return NetworkStatus.NotReachable;
        return NetworkStatus.ReachableViaWiFiNetwork;
    }

    public static NetworkStatus LocalWifiConnectionStatus()
    {
        NetworkReachabilityFlags flags;
        if (IsAdHocWiFiNetworkAvailable(out flags))
        {
            if ((flags & NetworkReachabilityFlags.IsDirect) != 0)
                return NetworkStatus.ReachableViaWiFiNetwork;
        }
        return NetworkStatus.NotReachable;
    }
}