[RESOLVED] [2005] Check for internet connection?

[Untouchab1e]

Hello!

When my application loads, it pings a website, and downloads an .xml file to check for a newer version of the program. However, i quickly found out, this resulted in an error if either a firewall is blocking this, or if the internet connection is disconnected. So, i put in some "if"'s and "else"'s. This partially solved the problem.

But on computers with no internet connection at all (as in not disconnected connections, but with no connections), an unhandled exception is thrown when the ping is run as there are no connections present. So is there a way to fix this, so that if there are no connections available, it just skips the whole thing?

Some code

If My.Computer.Network.Ping("http://connect-utb.byethost8.com", 1000) Then                  My.Computer.Network.DownloadFile(remotefile, localfile)  
Else
End if

[Bulldog]

Here is some code that detects whether a URL is accessible, its best to check two or three well known sites (such as google, yahoo etc.) in order to determine if a connection is available.

Public Function CheckURLExists(ByVal site As String) As Boolean
        Dim objUrl As New System.Uri(site)
        Dim objWebReq As System.Net.WebRequest
        Dim objResp As System.Net.WebResponse
        objWebReq = System.Net.WebRequest.Create(objUrl)
        Dim Success As Boolean
        Try
            objResp = objWebReq.GetResponse
            objResp.Close()
            Success = True
        Catch ex As Exception
            Success = False
        End Try
        objWebReq = Nothing
        Return Success
    End Function

Note that there is an oddity with this function, I'm not sure whether this is a bug in the IDE or what, but it always catches an exception correctly when run after a build, but the try/catch does not always catch an exception when run within the IDE.

[highflight1985]

Put the code in a Try/Catch statement?

Since the code given above has an oddity about it when run in the IDE, why not just replace it with your ping code?

[BrendanDavis]

This is what I do:

Private Function internetConnection() As Boolean
 
        Dim url As New System.Uri("http://www.yoursite.com/")
        Dim request As System.Net.WebRequest = System.Net.WebRequest.Create(url)
        Dim response As System.Net.WebResponse = request.GetResponse()
 
        Try
            response.Close()
            request = Nothing : Return True
        Catch ex As Exception
            request = Nothing : Return False
        End Try
 
    End Function

Syntax:

If internetConnection() = True Then
            Label1.Text = "Connected"
        Else : Label1.Text = "Not Connected"
        End If

[Untouchab1e]

Thanks for reply, but sadly, this did not solve my problem. Again, if my program is used on a pc with no internet connection available what so ever (not disconnected or connect, just no internet connections at all, as in "Network Connections" showing up empty.. just to get the point through), an unhandled exception is thrown.

EDIT: This also happens if the internet connection is disabled..

Anyone?

Cheers!

[highflight1985]

I suggested the Try/Catch statement. If the user has the condition which you describe, then you can fairly assume they don't have internet access. If the code you're trying is causing an error when the condition you describe occurs, then a Try/Catch statement should work? Are you using a Try/Catch statement?

[Untouchab1e]

Im using the Code BrendanDavis posted

Try
            response.Close()
            request = Nothing : Return True
        Catch ex As Exception
            request = Nothing : Return False
        End Try

So yes, im using a try/catch statement..

I get the following error when trying to run it with no internet connection:

The remote name could not be resolved

[highflight1985]

Exactly which line causes your error?

[Untouchab1e]

Dim response As System.Net.WebResponse = request.GetResponse()

[highflight1985]

Try moving that line to within the Try/Catch statement. If you're using his code exactly, it's outside of the Try/Catch...

EDIT: For that matter, try moving the entire bit of the function code (all the declarations) to within the try/catch statement.

[Untouchab1e]

That solved it! Thank you so much!

[highflight1985]

Glad to finally be able to help someone instead of being the one bening helped.

For my future copy-and-pasting:

Private Function internetConnection() As Boolean
 
        Dim url As New System.Uri("http://www.yoursite.com/")
        Dim request As System.Net.WebRequest = System.Net.WebRequest.Create(url)
        Dim response As System.Net.WebResponse = request.GetResponse()
 
        Try
            Dim url As New System.Uri("http://www.yoursite.com/")
            Dim request As System.Net.WebRequest = System.Net.WebRequest.Create(url)
            Dim response As System.Net.WebResponse = request.GetResponse()
            response.Close()
            request = Nothing : Return True
        Catch ex As Exception
            request = Nothing : Return False
        End Try
 
    End Function

If internetConnection() = True Then
            Label1.Text = "Connected"
        Else : Label1.Text = "Not Connected"
        End If