檢查互聯網連接

Question

我需要我的應用程序來檢查我的用戶計算機上的互聯網連接。如果有，則顯示圖像，如果不存在，則顯示不同的圖像。下面是我用得到這個工作的代碼：

Private Sub Window_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded 

    If NetworkInformation.NetworkInterface.GetIsNetworkAvailable Then 
     Dim bi1 As New BitmapImage 
     bi1.BeginInit() 
     bi1.UriSource = New Uri("Images\greenbar.png", UriKind.Relative) 
     bi1.EndInit() 
     Image2.Source = bi1 

    Else 
     Dim bi2 As New BitmapImage 
     bi2.BeginInit() 
     bi2.UriSource = New Uri("Images\redbar.png", UriKind.Relative) 
     bi2.EndInit() 
     Image2.Source = bi2 
     MessageBox.Show("INTERNET CONNECTION NOT DETECTED") 
     MessageBox.Show("You must be connected to the internet to use some aspects of this application.") 
     MessageBox.Show("Please re-establish connection to the Internet and try again, thank you.") 
     Me.Close() 

    End If 
End Sub 

，我決定改變我的默認網關（從而使其看起來好像我失去了連接），以測試這是我自己的電腦上。但是我意識到代碼仍然顯示我已連接。所以我認爲它只是檢查接口的連接性 - 在這種情況下，我是連接到路由器（這是事實，我已連接到路由器）。

所以，問題：如何檢查用戶的PC是否實際連接到互聯網？我閱讀了文章What is the best way to check for Internet connectivity using .NET?，但它是用C＃編寫的，我不明白這一點。

Answer 1

可以使用this tool到C＃轉換爲VB.NET或反之亦然：

Public Shared Function CheckForInternetConnection() As Boolean 
    Try 
     Using client = New WebClient() 
      Using stream = client.OpenRead("http://www.google.com") 
       Return True 
      End Using 
     End Using 
    Catch 
     Return False 
    End Try 
End Function 

順便說一句，你使用任何檢查網絡連接是否可用與否NetworkInterface.GetIsNetworkAvailable方法 - 不互聯網連接。

如果任何網絡接口被標記爲「up」並且不是環回或隧道接口，則認爲網絡連接可用。

Answer 2

或者使用此代碼

If My.Computer.Network.IsAvailable Then 
    MsgBox("Computer is connected.") 
Else 
    MsgBox("Computer is not connected.") 
End If 

Answer 3

If My.Computer.Network.Ping("www.Google.com") Then 
... 
End If 

Answer 4

你可以使用this，這應有助於你出去VB & C＃版本：

Public Function IsConnectionAvailable() As Boolean 
    ' Returns True if connection is available 
    ' Replace www.yoursite.com with a site that 
    ' is guaranteed to be online - perhaps your 
    ' corporate site, or microsoft.com 
    Dim objUrl As New System.Uri("http://www.google.com/") 
    ' Setup WebRequest 
    Dim objWebReq As System.Net.WebRequest 
    objWebReq = System.Net.WebRequest.Create(objUrl) 
    objWebReq.Proxy = Nothing 
    Dim objResp As System.Net.WebResponse 
    Try 
     ' Attempt to get response and return True 
     objResp = objWebReq.GetResponse 
     objResp.Close() 
     objWebReq = Nothing 
     Return True 
    Catch ex As Exception 
     ' Error, exit and return False 
     objResp.Close() 
     objWebReq = Nothing 
     Return False 
    End Try 
End Function 

Answer 5

Public Function IsConnectionAvailable() As Boolean 
    ' Returns True if connection is available 
    ' Replace www.yoursite.com with a site that 
    ' is guaranteed to be online - perhaps your 
    ' corporate site, or microsoft.com 
    Dim objUrl As New System.Uri("http://www.yoursite.com/") 
    ' Setup WebRequest 
    Dim objWebReq As System.Net.WebRequest 
    objWebReq = System.Net.WebRequest.Create(objUrl) 
    Dim objResp As System.Net.WebResponse 
    Try 
     ' Attempt to get response and return True 
     objResp = objWebReq.GetResponse 
     objResp.Close() 
     objWebReq = Nothing 
     Return True 
    Catch ex As Exception 
     ' Error, exit and return False 
     objResp.Close() 
     objWebReq = Nothing 
     Return False 
    End Try 


'Here’s how you might use this function in your application: 

If IsConnectionAvailable() = True Then 
    MessageBox.Show("You are online!") 
End If 

Answer 6

下面將檢查網絡連接可用性和Int ernet連接：

If My.Computer.Network.IsAvailable Then 

    Try 
     If My.Computer.Network.Ping("www.Google.com") Then 
      Infolabel.Text = "Computer is connected to the internet" 
     Else 
      Infolabel.Text = "Computer is not connected to the internet" 
     End If 
    Catch 

    End Try 

Else 
    Infolabel.Text = "Computer is not connected to the internet" 
End If