Credit: Neil Cowburn

C# Version:

using System;
using System.Net;

public class Net
{
    protected Net() {}

    public static bool IsWebAccessible()  // Call this class as follows:  bool bResponse = Net.IsWebAccessible;
    {
        HttpWebRequest hwrRequest;
        HttpWebResponse hwrResponse;

        string strUrl = @"http://www.microsoft.com/";
        bool bConnected = false;

        try
        {
            hwrRequest = (HttpWebRequest)WebRequest.Create(strUrl);
            hwrResponse = (HttpWebResponse)hwrRequest.GetResponse();

            if(hwrResponse.StatusCode == HttpStatusCode.OK)
            {
                bConnected = true;
            }
            hwrResponse.GetResponseStream().Close();
        }
        catch(WebException we)
        {
            bConnected = false;
        }
        catch(Exception ex)
        {
            bConnected = false;
        }
        finally
        {
            hwrRequest = null;
            hwrResponse = null;
        }

       return bConnected;
    }
}

VB .NET Version

Imports System
Imports System.Net

Public Class Net

    Protected Sub New()
    End Sub

    Public Shared Function IsWebAccessible() As Boolean

        Dim hwrRequest As HttpWebRequest
        Dim hwrResponse As HttpWebResponse

        Dim strUrl As String = "http://www.microsoft.com/"
        Dim bConnected As Boolean = False

        Try
            hwrRequest = CType(WebRequest.Create(strUrl), HttpWebRequest)
            hwrResponse = CType(hwrRequest.GetResponse(), HttpWebResponse)

            If hwrResponse.StatusCode = HttpStatusCode.OK Then
                bConnected = True
            End If
            hwrResponse.GetResponseStream().Close

        Catch we As WebException
            bConnected = False
        Catch ex As Exception
            bConnected = False
        Finally
            hwrRequest = Nothing
            hwrResponse = Nothing
        End Try

        Return bConnected

    End Function

End Class

Posted modifications (hwrResponse.GetResponseStream().Close()) to prevent lock up on multiple calls. (Credit Neelima Godugu)

As I set
hwrRequest.Timeout = 5;

but for the unknown host it still takes about 50s to return false.
Why's that?

quote:

---

Originally posted by alho

As I set
hwrRequest.Timeout = 5;

but for the unknown host it still takes about 50s to return false.
Why's that?

---

I dont know for sure, but I do know that if you do something like:
Socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, 10000);
Socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 10000);

those timeout values apply only AFTER the connection has been established. AFAIK there is no way to adjust the timeout when trying to establish an initial connection attempt.

I have read an article about how to test the network connectivity but i don't remember the url. But i thinks this method is more efficient to test the network available.


try
{
string hostname = Dns.GetHostName();
IPHostEntry thishost = Dns.GetHostByName(hostname);
string ipaddress = thishost.AddressList[0].ToString();
ret = !ipaddress.Equals(IPAddress.Parse("127.0.0.1").ToString());
}
catch
{
throw new Exception("No network connection.");
}


Have fun.