Develop Reference

What the best practice for determine connection to internet? [duplicate]

What is the fastest and most efficient way to check for Internet connectivity in .NET?

You could use this code, which should also work in Iran and China-
public static bool CheckForInternetConnection(int timeoutMs = 10000, string url = null)
{
try
{
url ??= CultureInfo.InstalledUICulture switch
{
{ Name: var n } when n.StartsWith("fa") => // Iran
"http://www.aparat.com",
{ Name: var n } when n.StartsWith("zh") => // China
"http://www.baidu.com",
_ =>
"http://www.gstatic.com/generate_204",
};
var request = (HttpWebRequest)WebRequest.Create(url);
request.KeepAlive = false;
request.Timeout = timeoutMs;
using (var response = (HttpWebResponse)request.GetResponse())
return true;
}
catch
{
return false;
}
}

There is absolutely no way you can reliably check if there is an internet connection or not (I assume you mean access to the internet).
You can, however, request resources that are virtually never offline, like pinging google.com or something similar. I think this would be efficient.
try {
Ping myPing = new Ping();
String host = "google.com";
byte[] buffer = new byte[32];
int timeout = 1000;
PingOptions pingOptions = new PingOptions();
PingReply reply = myPing.Send(host, timeout, buffer, pingOptions);
return (reply.Status == IPStatus.Success);
}
catch (Exception) {
return false;
}

Instead of checking, just perform the action (web request, mail, ftp, etc.) and be prepared for the request to fail, which you have to do anyway, even if your check was successful.
Consider the following:
1 - check, and it is OK
2 - start to perform action
3 - network goes down
4 - action fails
5 - lot of good your check did
If the network is down your action will fail just as rapidly as a ping, etc.
1 - start to perform action
2 - if the net is down(or goes down) the action will fail

NetworkInterface.GetIsNetworkAvailable is very unreliable. Just have some VMware or other LAN connection and it will return wrong result.
Also about Dns.GetHostEntry method I were just concerned about whether test URL might be blocked in the environment where my application going to deploy.
So another way I found out is using InternetGetConnectedState method.
My code is
[System.Runtime.InteropServices.DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState(out int Description, int ReservedValue);
public static bool CheckNet()
{
int desc;
return InternetGetConnectedState(out desc, 0);
}

Pinging google.com introduces a DNS resolution dependency. Pinging 8.8.8.8 is fine but Google is several hops away from me. All I need to do is to ping the nearest thing to me that is on the internet.
I can use Ping's TTL feature to ping hop #1, then hop #2, etc, until I get a reply from something that is on a routable address; if that node is on a routable address then it is on the internet. For most of us, hop #1 will be our local gateway/router, and hop #2 will be the first point on the other side of our fibre connection or whatever.
This code works for me, and responds quicker than some of the other suggestions in this thread because it is pinging whatever is nearest to me on the internet.
using System.Diagnostics;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Threading.Tasks;
public static async Task<bool> IsConnectedToInternetAsync()
{
const int maxHops = 30;
const string someFarAwayIpAddress = "8.8.8.8";
// Keep pinging further along the line from here to google
// until we find a response that is from a routable address
for (int ttl = 1; ttl <= maxHops; ttl++)
{
var options = new PingOptions(ttl, true);
byte[] buffer = new byte[32];
PingReply reply;
try
{
using (var pinger = new Ping())
{
reply = await pinger.SendPingAsync(someFarAwayIpAddress, 10000, buffer, options);
}
}
catch (PingException pingex)
{
Debug.Print($"Ping exception (probably due to no network connection or recent change in network conditions), hence not connected to internet. Message: {pingex.Message}");
return false;
}
string address = reply.Address?.ToString() ?? null;
Debug.Print($"Hop #{ttl} is {address}, {reply.Status}");
if (reply.Status != IPStatus.TtlExpired && reply.Status != IPStatus.Success)
{
Debug.Print($"Hop #{ttl} is {reply.Status}, hence we are not connected.");
return false;
}
if (IsRoutableAddress(reply.Address))
{
Debug.Print("That's routable, so we must be connected to the internet.");
return true;
}
}
return false;
}
private static bool IsRoutableAddress(IPAddress addr)
{
if (addr == null)
{
return false;
}
else if (addr.AddressFamily == AddressFamily.InterNetworkV6)
{
return !addr.IsIPv6LinkLocal && !addr.IsIPv6SiteLocal;
}
else // IPv4
{
byte[] bytes = addr.GetAddressBytes();
if (bytes[0] == 10)
{ // Class A network
return false;
}
else if (bytes[0] == 172 && bytes[1] >= 16 && bytes[1] <= 31)
{ // Class B network
return false;
}
else if (bytes[0] == 192 && bytes[1] == 168)
{ // Class C network
return false;
}
else
{ // None of the above, so must be routable
return true;
}
}
}

A test for internet connection by pinging Google:
new Ping().Send("www.google.com.mx").Status == IPStatus.Success

I disagree with people who are stating: "What's the point in checking for connectivity before performing a task, as immediately after the check the connection may be lost".
Surely there is a degree of uncertainty in many programming tasks we as developers undertake, but reducing the uncertainty to a level of acceptance is part of the challenge.
I recently ran into this problem making an application which including a mapping feature which linked to an on-line tile server. This functionality was to be disabled where a lack of internet connectivity was noted.
Some of the responses on this page were very good, but did however cause a lot of performance issues such as hanging, mainly in the case of the absence of connectivity.
Here is the solution that I ended up using, with the help of some of these answers and my colleagues:
// Insert this where check is required, in my case program start
ThreadPool.QueueUserWorkItem(CheckInternetConnectivity);
}
void CheckInternetConnectivity(object state)
{
if (System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
{
using (WebClient webClient = new WebClient())
{
webClient.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.BypassCache);
webClient.Proxy = null;
webClient.OpenReadCompleted += webClient_OpenReadCompleted;
webClient.OpenReadAsync(new Uri("<url of choice here>"));
}
}
}
volatile bool internetAvailable = false; // boolean used elsewhere in code
void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
if (e.Error == null)
{
internetAvailable = true;
Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() =>
{
// UI changes made here
}));
}
}

I have seen all the options listed above and the only viable option to check wither the internet is available or not is the "Ping" option.
Importing [DllImport("Wininet.dll")] and System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces() Or any other variation of the NetworkInterface class does not work well in detecting the availability of the network.These Methods only check if the network cable is plugged in or not.
The "Ping option"
if(Connection is available) returns true
if(Connection is not available and the network cable is plugged in) returns false
if(Network cable is not plugged in) Throws an exception
The NetworkInterface
if(Internet Is available)Returns True
if(Internet is not Available and Network Cable is Plugged in ) Returns True
if(Network Cable is Not Plugged in )returns false
The [DllImport("Wininet.dll")]
if(Internet Is available)Returns True
if(Internet is not Available and Network Cable is Plugged in ) Returns True
if(Network Cable is Not Plugged in )returns false
So in case of [DllImport("Wininet.dll")] and NetworkInterface There is no way of knowing if internet connection is available.

Does not solve the problem of network going down between checking and running your code
but is fairly reliable
public static bool IsAvailableNetworkActive()
{
// only recognizes changes related to Internet adapters
if (System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
{
// however, this will include all adapters -- filter by opstatus and activity
NetworkInterface[] interfaces = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
return (from face in interfaces
where face.OperationalStatus == OperationalStatus.Up
where (face.NetworkInterfaceType != NetworkInterfaceType.Tunnel) && (face.NetworkInterfaceType != NetworkInterfaceType.Loopback)
select face.GetIPv4Statistics()).Any(statistics => (statistics.BytesReceived > 0) && (statistics.BytesSent > 0));
}
return false;
}

Here's how it is implemented in Android.
As a proof of concept, I translated this code to C#:
var request = (HttpWebRequest)WebRequest.Create("http://g.cn/generate_204");
request.UserAgent = "Android";
request.KeepAlive = false;
request.Timeout = 1500;
using (var response = (HttpWebResponse)request.GetResponse())
{
if (response.ContentLength == 0 && response.StatusCode == HttpStatusCode.NoContent)
{
//Connection to internet available
}
else
{
//Connection to internet not available
}
}

private bool ping()
{
System.Net.NetworkInformation.Ping pingSender = new System.Net.NetworkInformation.Ping();
System.Net.NetworkInformation.PingReply reply = pingSender.Send(address);
if (reply.Status == System.Net.NetworkInformation.IPStatus.Success)
{
return true;
}
else
{
return false;
}
}

Try to avoid testing connections by catching the exception. because we really Expect that sometimes we may lose network connection.
if (NetworkInterface.GetIsNetworkAvailable() &&
new Ping().Send(new IPAddress(new byte[] { 8, 8, 8, 8 }),2000).Status == IPStatus.Success)
//is online
else
//is offline

I wouldn't think it's impossible, just not straightforward.
I've built something like this, and yes it's not perfect, but the first step is essential: to check if there's any network connectivity. The Windows Api doesn't do a great job, so why not do a better job?
bool NetworkIsAvailable()
{
var all = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
foreach (var item in all)
{
if (item.NetworkInterfaceType == NetworkInterfaceType.Loopback)
continue;
if (item.Name.ToLower().Contains("virtual") || item.Description.ToLower().Contains("virtual"))
continue; //Exclude virtual networks set up by VMWare and others
if (item.OperationalStatus == OperationalStatus.Up)
{
return true;
}
}
return false;
}
It's pretty simple, but it really helps improve the quality of the check, especially when you want to check various proxy configurations.
So:
Check whether there's network connectivity (make this really good, maybe even have logs sent back to developers when there are false positives to improve the NetworkIsAvailable function)
HTTP Ping
(Cycle through Proxy configurations with HTTP Pings on each)

Another option is the Network List Manager API which is available for Vista and Windows 7. MSDN article here. In the article is a link to download code samples which allow you to do this:
AppNetworkListUser nlmUser = new AppNetworkListUser();
Console.WriteLine("Is the machine connected to internet? " + nlmUser.NLM.IsConnectedToInternet.ToString());
Be sure to add a reference to Network List 1.0 Type Library from the COM tab... which will show up as NETWORKLIST.

I personally find the answer of Anton and moffeltje best, but I added a check to exclude virtual networks set up by VMWare and others.
public static bool IsAvailableNetworkActive()
{
// only recognizes changes related to Internet adapters
if (!System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable()) return false;
// however, this will include all adapters -- filter by opstatus and activity
NetworkInterface[] interfaces = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
return (from face in interfaces
where face.OperationalStatus == OperationalStatus.Up
where (face.NetworkInterfaceType != NetworkInterfaceType.Tunnel) && (face.NetworkInterfaceType != NetworkInterfaceType.Loopback)
where (!(face.Name.ToLower().Contains("virtual") || face.Description.ToLower().Contains("virtual")))
select face.GetIPv4Statistics()).Any(statistics => (statistics.BytesReceived > 0) && (statistics.BytesSent > 0));
}

Introduction
In some scenarios you need to check whether internet is available or not using C# code in windows applications. May be to download or upload a file using internet in windows forms or to get some data from database which is at remote location, in these situations internet check is compulsory.
There are some ways to check internet availability using C# from code behind. All such ways are explained here including their limitations.
InternetGetConnectedState(wininet)
The 'wininet' API can be used to check the local system has active internet connection or not. The namespace used for this is 'System.Runtime.InteropServices' and import the dll 'wininet.dll' using DllImport. After this create a boolean variable with extern static with a function name InternetGetConnectedState with two parameters description and reservedValue as shown in example.
Note: The extern modifier is used to declare a method that is implemented externally. A common use of the extern modifier is with the DllImport attribute when you are using Interop services to call into unmanaged code. In this case, the method must also be declared as static.
Next create a method with name 'IsInternetAvailable' as boolean. The
above function will be used in this method which returns internet
status of local system
[DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState(out int description, int reservedValue);
public static bool IsInternetAvailable()
{
try
{
int description;
return InternetGetConnectedState(out description, 0);
}
catch (Exception ex)
{
return false;
}
}
GetIsNetworkAvailable
The following example uses the GetIsNetworkAvailable method to determine if a network connection is available.
if (System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
{
System.Windows.MessageBox.Show("This computer is connected to the internet");
}
else
{
System.Windows.MessageBox.Show("This computer is not connected to the internet");
}
Remarks (As per MSDN): A network connection is considered to be available if any network interface is marked "up" and is not a loopback or tunnel interface.
There are many cases in which a device or computer is not connected to a useful network but is still considered available and GetIsNetworkAvailable will return true. For example, if the device running the application is connected to a wireless network that requires a proxy, but the proxy is not set, GetIsNetworkAvailable will return true. Another example of when GetIsNetworkAvailable will return true is if the application is running on a computer that is connected to a hub or router where the hub or router has lost the upstream connection.
Ping a hostname on the network
Ping and PingReply classes allows an application to determine whether a remote computer is accessible over the network by getting reply from the host. These classes are available in System.Net.NetworkInformation namespace. The following example shows how to ping a host.
protected bool CheckConnectivity(string ipAddress)
{
bool connectionExists = false;
try
{
System.Net.NetworkInformation.Ping pingSender = new System.Net.NetworkInformation.Ping();
System.Net.NetworkInformation.PingOptions options = new System.Net.NetworkInformation.PingOptions();
options.DontFragment = true;
if (!string.IsNullOrEmpty(ipAddress))
{
System.Net.NetworkInformation.PingReply reply = pingSender.Send(ipAddress);
connectionExists = reply.Status ==
System.Net.NetworkInformation.IPStatus.Success ? true : false;
}
}
catch (PingException ex)
{
Logger.LogException(ex.Message, ex);
}
return connectionExists;
}
Remarks (As per MSDN): Applications use the Ping class to detect whether a remote computer is reachable. Network topology can determine whether Ping can successfully contact a remote host. The presence and configuration of proxies, network address translation (NAT) equipment, or firewalls can prevent Ping from succeeding. A successful Ping indicates only that the remote host can be reached on the network; the presence of higher level services (such as a Web server) on the remote host is not guaranteed.
Comments/Suggestions are invited. Happy coding......!

The accepted answer succeeds quickly but is very slow to fail when there is no connection. So I wanted to build a robust connection check that would fail faster.
Pinging was said to not be supported in all environments, so I started with the accepted answer and added a WebClient from here with a custom timeout. You can pick any timeout, but 3 seconds worked for me while connected via wifi. I tried adding a fast iteration (1 second), then a slow iteration (3 seconds) if the first one fails. But that made no sense since both iterations would always fail (when not connected) or always succeed (when connected).
I'm connecting to AWS since I want to upload a file when the connection test passes.
public static class AwsHelpers
{
public static bool GetCanConnectToAws()
{
try
{
using (var client = new WebClientWithShortTimeout())
using (client.OpenRead("https://aws.amazon.com"))
return true;
}
catch
{
return false;
}
}
}
public class WebClientWithShortTimeout: WebClient
{
protected override WebRequest GetWebRequest(Uri uri)
{
var webRequest = base.GetWebRequest(uri);
webRequest.Timeout = 5000;
return webRequest;
}
}

If you want to notify the user/take action whenever a network/connection change occur.
Use NLM API:
https://msdn.microsoft.com/en-us/library/ee264321.aspx
http://www.codeproject.com/Articles/34650/How-to-use-the-Windows-NLM-API-to-get-notified-of

public static bool Isconnected = false;
public static bool CheckForInternetConnection()
{
try
{
Ping myPing = new Ping();
String host = "google.com";
byte[] buffer = new byte[32];
int timeout = 1000;
PingOptions pingOptions = new PingOptions();
PingReply reply = myPing.Send(host, timeout, buffer, pingOptions);
if (reply.Status == IPStatus.Success)
{
return true;
}
else if (reply.Status == IPStatus.TimedOut)
{
return Isconnected;
}
else
{
return false;
}
}
catch (Exception)
{
return false;
}
}
public static void CheckConnection()
{
if (CheckForInternetConnection())
{
Isconnected = true;
}
else
{
Isconnected = false;
}
}

bool bb = System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable();
if (bb == true)
MessageBox.Show("Internet connections are available");
else
MessageBox.Show("Internet connections are not available");

Multi threaded version of ping:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net.NetworkInformation;
using System.Threading;
namespace OnlineCheck
{
class Program
{
static bool isOnline = false;
static void Main(string[] args)
{
List<string> ipList = new List<string> {
"1.1.1.1", // Bad ip
"2.2.2.2",
"4.2.2.2",
"8.8.8.8",
"9.9.9.9",
"208.67.222.222",
"139.130.4.5"
};
int timeOut = 1000 * 5; // Seconds
List<Thread> threadList = new List<Thread>();
foreach (string ip in ipList)
{
Thread threadTest = new Thread(() => IsOnline(ip));
threadList.Add(threadTest);
threadTest.Start();
}
Stopwatch stopwatch = Stopwatch.StartNew();
while (!isOnline && stopwatch.ElapsedMilliseconds <= timeOut)
{
Thread.Sleep(10); // Cooldown the CPU
}
foreach (Thread thread in threadList)
{
thread.Abort(); // We love threads, don't we?
}
Console.WriteLine("Am I online: " + isOnline.ToYesNo());
Console.ReadKey();
}
static bool Ping(string host, int timeout = 3000, int buffer = 32)
{
bool result = false;
try
{
Ping ping = new Ping();
byte[] byteBuffer = new byte[buffer];
PingOptions options = new PingOptions();
PingReply reply = ping.Send(host, timeout, byteBuffer, options);
result = (reply.Status == IPStatus.Success);
}
catch (Exception ex)
{
}
return result;
}
static void IsOnline(string host)
{
isOnline = Ping(host) || isOnline;
}
}
public static class BooleanExtensions
{
public static string ToYesNo(this bool value)
{
return value ? "Yes" : "No";
}
}
}

Building on #ChaosPandion's answer, to be as sure as possible that the result is correct you can include multiple big sites like others have pointed out. However this should be done asynchronously to avoid too long wait times. Also the WebRequest, HttpWebRequest and HttpWebResponse classes are now obsolete and should be replaced by HttpClient. The following example takes into account the above:
public static async Task<bool> CheckForInternetConnection(TimeSpan? timeoutMs = null, List<string> urls = null)
{
if (timeoutMs == null)
{
timeoutMs = TimeSpan.FromSeconds(10);
}
var culture = CultureInfo.InstalledUICulture;
if (urls == null)
{
urls = new List<string>();
if (culture.Name.StartsWith("fa")) // Iran
urls.Add("http://www.aparat.com");
else if (culture.Name.StartsWith("zh")) // China
urls.Add("http://www.baidu.com");
else
{
urls.Add("https://www.apple.com/");
urls.Add("https://www.gstatic.com/generate_204");
}
}
var client = new HttpClient();
client.Timeout = (TimeSpan)timeoutMs;
List<Task<string>> tasks = new List<Task<string>>();
int unresponsiveUrlCount = 0;
foreach (var url in urls)
{
tasks.Add(client.GetStringAsync(url));
}
Task aggregationTask = null;
try
{
aggregationTask = Task.WhenAll(tasks);
await aggregationTask;
}
catch (Exception)
{
if (aggregationTask?.Exception?.InnerExceptions != null && aggregationTask.Exception.InnerExceptions.Any())
{
foreach (var innerEx in aggregationTask.Exception.InnerExceptions)
{
unresponsiveUrlCount++;
}
}
}
return unresponsiveUrlCount < urls.Count;
}
This method checks all the urls in the list and if they are all inaccessible then it returns false. I have added apple's url, because in my case it loads pretty fast, but it can be replaced with any url.

Use NetworkMonitor to monitoring network state and internet connection.
Sample:
namespace AmRoNetworkMonitor.Demo
{
using System;
internal class Program
{
private static void Main()
{
NetworkMonitor.StateChanged += NetworkMonitor_StateChanged;
NetworkMonitor.StartMonitor();
Console.WriteLine("Press any key to stop monitoring.");
Console.ReadKey();
NetworkMonitor.StopMonitor();
Console.WriteLine("Press any key to close program.");
Console.ReadKey();
}
private static void NetworkMonitor_StateChanged(object sender, StateChangeEventArgs e)
{
Console.WriteLine(e.IsAvailable ? "Is Available" : "Is Not Available");
}
}
}

For my application we also test by download tiny file.
string remoteUri = "https://www.microsoft.com/favicon.ico"
WebClient myWebClient = new WebClient();
try
{
byte[] myDataBuffer = myWebClient.DownloadData (remoteUri);
if(myDataBuffer.length > 0) // Or add more validate. eg. checksum
{
return true;
}
}
catch
{
return false;
}
Also. Some ISP may use middle server to cache file. Add random unused parameter eg. https://www.microsoft.com/favicon.ico?req=random_number
Can prevent caching.

I am having issue on those method on my 3g Router/modem, because if internet is disconnected the router redirects the page to its response page, so you still get a steam and your code think there is internet.
Apples (or others) have a hot-spot-dedection page which always returns a certain response. The following sample returns "Success" response. So you will be exactly sure you could connect the internet and get real response !
public static bool CheckForInternetConnection()
{
try
{
using (var webClient = new WebClient())
using (var stream = webClient.OpenRead("http://captive.apple.com/hotspot-detect.html"))
{
if (stream != null)
{
//return true;
stream.ReadTimeout = 1000;
using (var reader = new StreamReader(stream, Encoding.UTF8, false))
{
string line;
while ((line = reader.ReadLine()) != null)
{
if (line == "<HTML><HEAD><TITLE>Success</TITLE></HEAD><BODY>Success</BODY></HTML>")
{
return true;
}
Console.WriteLine(line);
}
}
}
return false;
}
}
catch
{
}
return false;
}

I have three tests for an Internet connection.
Reference System.Net and System.Net.Sockets
Add the following test functions:
Test 1
public bool IsOnlineTest1()
{
try
{
IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
return true;
}
catch (SocketException ex)
{
return false;
}
}
Test 2
public bool IsOnlineTest2()
{
try
{
IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
return true;
}
catch (SocketException ex)
{
return false;
}
}
Test 3
public bool IsOnlineTest3()
{
System.Net.WebRequest req = System.Net.WebRequest.Create("https://www.google.com");
System.Net.WebResponse resp = default(System.Net.WebResponse);
try
{
resp = req.GetResponse();
resp.Close();
req = null;
return true;
}
catch (Exception ex)
{
req = null;
return false;
}
}
Performing the tests
If you make a Dictionary of String and Boolean called CheckList, you can add the results of each test to CheckList.
Now, recurse through each KeyValuePair using a for...each loop.
If CheckList contains a Value of true, then you know there is an Internet connection.

public static bool HasConnection()
{
try
{
System.Net.IPHostEntry i = System.Net.Dns.GetHostEntry("www.google.com");
return true;
}
catch
{
return false;
}
}
That works

check internet connection available or not in c#

I am using below method to check internet connection available or not in c#
and I was using it from What is the best way to check for Internet connectivity using .NET?
public static bool CheckForInternetConnection()
{
try
{
using (var client = new WebClient())
using (var stream = client.OpenRead("http://www.google.com"))
{
return true;
}
}
catch
{
return false;
}
}
above method works but I am facing problem, some time it takes a long time to rerun value, may be internet speed, but when I open Google.com in web browser then link open in a second, so why it is taking time to get result from C#

You can check whether internet is available or not like this:
ConnectionProfile internetConnectionProfile = Windows.Networking.Connectivity.NetworkInformation.GetInternetConnectionProfile();
if (internetConnectionProfile == null)
{
//logic ....
}
if (internetConnectionProfile != null)
{
this.IsInternetAvailable = internetConnectionProfile.GetNetworkConnectivityLevel() ==
NetworkConnectivityLevel.InternetAccess;
if (internetConnectionProfile.NetworkAdapter.IanaInterfaceType != 71)// Connection is not a Wi-Fi connection.
{
var isRoaming = internetConnectionProfile.GetConnectionCost().Roaming;
//user is Low on Data package only send low data.
var isLowOnData = internetConnectionProfile.GetConnectionCost().ApproachingDataLimit;
//User is over limit do not send data
var isOverDataLimit = internetConnectionProfile.GetConnectionCost().OverDataLimit;
IsWifiConnected = true;
}
else //Connection is a Wi-Fi connection. Data restrictions are not necessary.
{
IsWifiConnected = true;
}
}

I think your TimeOut is not working because of Domain Name Resolution. I you are proxy behind you must configure it on app.config file.
Check that example, I hope it helps you. I did it using .Net 4.0.
static bool CheckForInternetConnection(int timeOut = 3000)
{
var task = CheckForInternetConnectionTask(timeOut);
return task.Wait(timeOut) && task.Result;
}
static Task<bool> CheckForInternetConnectionTask(int timeOut = 3000)
{
return Task.Factory.StartNew
(() =>
{
try
{
var client = (HttpWebRequest) WebRequest.Create("http://google.com/");
client.Method = "HEAD";
client.Timeout = timeOut;
using (var response = client.GetResponse())
using (response.GetResponseStream())
{
return true;
}
}
catch
{
return false;
}
});
}
And a sample call:
Console.WriteLine("CheckForInternetConnection -> {0}", CheckForInternetConnection());
If you are proxy behind, do not forget to add proxy configuration on app.config file.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.net>
<defaultProxy enabled="true">
<proxy proxyaddress="http://127.0.0.1:1111" usesystemdefault="True"/>
</defaultProxy>
</system.net>
</configuration>

public static bool ConnectionTest()
{
try
{
string site = "http://www.google.com/";
TcpClient client = TcpClient(site, 80);
client.Close();
return true;
}
catch (Exception)
{
return false;
}
}
Something like this should be faster.

Getting internet connection status from WinRT

Below if the code I've been using for some time to get the connection status of the device that my store app in running on. What appears to have happened recently is, whilst it still finds the correct connection profile, it returns the level as Local, rather than Internet access.
IReadOnlyList<ConnectionProfile> p = NetworkInformation.GetConnectionProfiles();
foreach (ConnectionProfile prof in p)
{
NetworkConnectivityLevel lev = prof.GetNetworkConnectivityLevel();
if (lev == NetworkConnectivityLevel.InternetAccess)
{
return true;
}
}
return false;
Can anyone tell me why this might be, and how I can persuade it that I do, in fact, have a working internet connection (which I can prove by being able to post this question :-) )?

try this one
private bool roaming;
private string connectionProfileInfo;
private async Task<bool> IsConnectedToInternet()
{
HttpWebRequest webReq;
HttpWebResponse resp = null;
// HttpStatusCode respcode;
Uri url = null;
url = new Uri("http://www.dartinnovations.com");
webReq = (HttpWebRequest)WebRequest.Create(url);
try
{
resp = (HttpWebResponse)await webReq.GetResponseAsync();
// Debug.WriteLine(resp.StatusCode);
webReq.Abort();
webReq = null;
url = null;
resp = null;
return true;
}
catch
{
webReq.Abort();
webReq = null;
return false;
}
}
private async Task<bool> CheckForConnection()
{
bool isConnected = await IsConnectedToInternet();
Debug.WriteLine(isConnected);
ConnectionProfile internetConnectionProfile = NetworkInformation.GetInternetConnectionProfile();
if (isConnected)
{
if (internetConnectionProfile != null)//Gets metereing info, Connectionprofile gives false positives when used to check for internet connectivity
{
Debug.WriteLine("internet available");
GetMeteringInformation(internetConnCectionProfile);
}
else
{
connectionProfileInfo = "Roaming information not available";
roaming = false;
// Debug.WriteLine("no connections");
}
return true;
}
return false;
}
private async Task GetMeteringInformation(ConnectionProfile connectionProfile)
{
ConnectionCost connectionCost = connectionProfile.GetConnectionCost();
roaming = connectionCost.Roaming;
connectionProfileInfo = "Over Data Limit :" + connectionCost.OverDataLimit + " | Approaching Data Limit :" +
connectionCost.ApproachingDataLimit;
}

Check internet connection (availability) in Windows 8

How to check internet connection availability in Windows 8,C# development ? I looked at MSDN but page has been deleted.

I use this snippet without problems:
public static bool IsInternet()
{
ConnectionProfile connections = NetworkInformation.GetInternetConnectionProfile();
bool internet = connections != null && connections.GetNetworkConnectivityLevel() == NetworkConnectivityLevel.InternetAccess;
return internet;
}

I had to use GetConnectionProfiles() and GetInternetConnectionProfile() to make it work across all devices.
class ConnectivityUtil
{
internal static bool HasInternetConnection()
{
var connections = NetworkInformation.GetConnectionProfiles().ToList();
connections.Add(NetworkInformation.GetInternetConnectionProfile());
foreach (var connection in connections)
{
if (connection == null)
continue;
if (connection.GetNetworkConnectivityLevel() == NetworkConnectivityLevel.InternetAccess)
return true;
}
return false;
}
}

For Windows Phone Following code may be usefull:
var networkInformation = NetworkInformation.GetConnectionProfiles();
if (networkInformation.Count == 0)
{
//no network connection
}

How to get IP of all hosts in LAN?

I need to list IP addresses of all connected hosts in my LAN.
What is the simplest way to do this?

You'll have to do a ping sweep. There's a Ping class in the System.Net namespace. Example follows. Also this is only possible if your computers don't have firewalls running. If they've got a firewall enabled, there's no way to determine this information short of doing SNMP queries on your switches.
System.Net.NetworkInformation.Ping p = new System.Net.NetworkInformation.Ping();
System.Net.NetworkInformation.PingReply rep = p.Send("192.168.1.1");
if (rep.Status == System.Net.NetworkInformation.IPStatus.Success)
{
//host is active
}
The other issue is to determine how large your network is. In most home situations, your network mask will be 24 bits. This means that its set to 255.255.255.0. If your gateway is 192.168.1.1, this means that valid addresses on your network will be 192.168.1.1 to 192.168.1.254. Here's an IP Calculator to help. You'll have to loop through each address and ping the address using the Ping class and check the PingReply.
If you're just looking for the information and aren't concerned with how you get it, you can use NMap. The command would be as follows
nmap -sP 192.168.1.0/24
EDIT:
As far as speed goes, since you're on a local network, you can cut down the timeout interval considerably as your machines shouldn't take more than 100 milliseconds to reply. You can also use SendAsync to ping them all in parallel. The following program will ping 254 address in under half a second.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.NetworkInformation;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Net.Sockets;
namespace ConsoleApplication1
{
class Program
{
static CountdownEvent countdown;
static int upCount = 0;
static object lockObj = new object();
const bool resolveNames = true;
static void Main(string[] args)
{
countdown = new CountdownEvent(1);
Stopwatch sw = new Stopwatch();
sw.Start();
string ipBase = "10.22.4.";
for (int i = 1; i < 255; i++)
{
string ip = ipBase + i.ToString();
Ping p = new Ping();
p.PingCompleted += new PingCompletedEventHandler(p_PingCompleted);
countdown.AddCount();
p.SendAsync(ip, 100, ip);
}
countdown.Signal();
countdown.Wait();
sw.Stop();
TimeSpan span = new TimeSpan(sw.ElapsedTicks);
Console.WriteLine("Took {0} milliseconds. {1} hosts active.", sw.ElapsedMilliseconds, upCount);
Console.ReadLine();
}
static void p_PingCompleted(object sender, PingCompletedEventArgs e)
{
string ip = (string)e.UserState;
if (e.Reply != null && e.Reply.Status == IPStatus.Success)
{
if (resolveNames)
{
string name;
try
{
IPHostEntry hostEntry = Dns.GetHostEntry(ip);
name = hostEntry.HostName;
}
catch (SocketException ex)
{
name = "?";
}
Console.WriteLine("{0} ({1}) is up: ({2} ms)", ip, name, e.Reply.RoundtripTime);
}
else
{
Console.WriteLine("{0} is up: ({1} ms)", ip, e.Reply.RoundtripTime);
}
lock(lockObj)
{
upCount++;
}
}
else if (e.Reply == null)
{
Console.WriteLine("Pinging {0} failed. (Null Reply object?)", ip);
}
countdown.Signal();
}
}
}
EDIT: After some use of it myself, I modified the program to output a count of how many IPs responded. There's a const bool that if set to true, will cause the program resolve the host names of the IPs. This significantly slows down the scan, though. (under half a second to 16 seconds) Also found that if the IP address is incorrectly specified (made a typo myself), the reply object can be null, so I handled that.

You would need to build an address range (e.g. 192.168.0.1 - 192.168.255.254) and ping each of those addresses. If a response is received, then that host is active.
Asynchronous Ping Tutorial:
http://www.geekpedia.com/tutorial234_Asynchronous-Ping-using-Csharp.html
However, some newer operating systems block ping requests (ICMP). This would need to be disabled in the firewall on each computer for you to receive a response.

You can do it all in managed code. I do it using System.DirectoryServices and System.Net. Basically I get the names of the local computers from DirectoryServices (handling domains and workgroups as I go) then get each host's IP addresses from System.Net.Dns. Here's everything packed into a handy class...
public class NetworkComputer {
private string _domain;
private string _name;
private IPAddress[] _addresses = null;
public string Domain { get { return _domain; } }
public string Name { get { return _name; } }
public IPAddress[] Addresses { get { return _addresses; } }
private NetworkComputer(string domain, string name) {
_domain = domain;
_name = name;
try { _addresses = Dns.GetHostAddresses(name); } catch { }
}
public static NetworkComputer[] GetLocalNetwork() {
var list = new List<NetworkComputer>();
using(var root = new DirectoryEntry("WinNT:")) {
foreach(var _ in root.Children.OfType<DirectoryEntry>()) {
switch(_.SchemaClassName) {
case "Computer":
list.Add(new NetworkComputer("", _.Name));
break;
case "Domain":
list.AddRange(_.Children.OfType<DirectoryEntry>().Where(__ => (__.SchemaClassName == "Computer")).Select(__ => new NetworkComputer(_.Name, __.Name)));
break;
}
}
}
return list.OrderBy(_ => _.Domain).ThenBy(_ => _.Name).ToArray();
}
}
Then just call the static method to get an array of your LAN computers...
var localComputers = NetworkComputer.GetLocalNetwork();

Nazim was correct. And krowe2's reply is factually incorrect. Switches absolutely forward broadcast traffic. You can send a ping to the subnet's broadcast address under the following conditions.
1.a) You are on the same subnet.
1.b) the gateway allows for IP direct broadcast
2.a) The subnet is not part of a fabric network.
2.b) If the subnet is part of a fabric, broadcast traffic is allowed on the subnet.
In about 80% of networks (and about 99.99% of networks using 192.168.1.1 as a gateway) this will work. I'm a network engineer and I do this all the time.
You CAN NOT rely on ICMP (ping) responses to validate the existence of a device on a network. The problem is that no device is required to listen to any traffic. Not ping, not SNMP, not NetBios. The only real way to be sure is to look at the ARP table.
You have to send out any kind of traffic to every IP in the subnet and look at your own ARP table. Because no device can get any traffic until resolve the MAC address of the IP on the local subnet. So before a device decides if it's going to listen to traffic or not, it has to respond to an ARP request. Your device then caches this in it's ARP table and can send frames with the right destination MAC to the other device.
On a Windows PC, the command line command is 'arp -a'. Linux is 'arp -n' if I recall correctly.

You could ping the adress range and note if a host responded. Of course, this will require the host to respond to the ping packets.

namespace WindowsFormsApplication1
{
class WifiInformation
{
static CountdownEvent countdown;
static int upCount = 0;
static object lockObj = new object();
const bool resolveNames = true;
static void Main(string[] args)
{
string ipBase = getIPAddress();
string[] ipParts = ipBase.Split('.');
ipBase = ipParts[0] + "." + ipParts[1] + "." + ipParts[2] + ".";
for (int i = 1; i < 255; i++)
{
string ip = ipBase + i.ToString();
Ping p = new Ping();
p.PingCompleted += new PingCompletedEventHandler(p_PingCompleted);
p.SendAsync(ip, 100, ip);
}
Console.ReadLine();
}
static void p_PingCompleted(object sender, PingCompletedEventArgs e)
{
string ip = (string)e.UserState;
if (e.Reply != null && e.Reply.Status == IPStatus.Success)
{
if (resolveNames)
{
string name;
try
{
IPHostEntry hostEntry = Dns.GetHostEntry(ip);
name = hostEntry.HostName;
}
catch (SocketException ex)
{
name = "?";
}
Console.WriteLine("{0} ({1}) is up: ({2} ms)", ip, name, e.Reply.RoundtripTime);
}
else
{
Console.WriteLine("{0} is up: ({1} ms)", ip, e.Reply.RoundtripTime);
}
lock (lockObj)
{
upCount++;
}
}
else if (e.Reply == null)
{
Console.WriteLine("Pinging {0} failed. (Null Reply object?)", ip);
}
}
public static string getIPAddress()
{
IPHostEntry host;
string localIP = "";
host = Dns.GetHostEntry(Dns.GetHostName());
foreach (IPAddress ip in host.AddressList)
{
if (ip.AddressFamily == AddressFamily.InterNetwork)
{
localIP = ip.ToString();
}
}
return localIP;
}
}
}

Instead of arranging a wild ping-party, you could possibly (I really don't know exactly!) use NetBIOS (request the netbios nametable somehow?) http://technet.microsoft.com/en-us/library/cc757216%28WS.10%29.aspx. Or why not ask your DHCP server?

Ping to the global broadcast ip address (192.168.1.255)
Normally we will get the reply from all the host connected to the LAN.. Or if you have any particular network for the lan, ping to that networks broadcast id (i.e the last ip address in that range ).
Then you can know all the ip address connected to the host in lan.