My vb code is supposed to send several variables to a server

My vb code is supposed to send several variables to a server and the server response is a fairly short string. I am using WebClient and it seems to work just fine. I store webclient.openread to a stream, read the stream, close the stream and the stream reader. I have even accounted for the "WebException" that is thrown when my code tries to OpenRead a url without an internet connection. So when I try to connect to the url without a connection I get the expected "The remote name could not be resolved." The problem comes when I reconnect my internet. The program doesn't connect to the URL and instead throws a different exception -- System.Net.WebException: Unable to connect to the remote server --> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond..." In other words it never connects to the URL again. It works if I close and reopen the program. How can I have the program recover from a disconnect?

Customer (name blocked for privacy)

OS: Windows Vista; Browser: Mozilla

Already Tried:
I have tried overriding the WebClient class that forces keepalive = false and connectionGroupName to generate a new Guid, to no avail.
The exception happens @
Dim data As Stream = client.OpenRead(url)
but I can't close data in the Catch section because it seems to have never been opened in the first place.

I'm working with VB.net 2008

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That was a good thought, but it's doing the same thing. When I disconnect my internet and try the code, I get the "no internet" response like i was expecting. But when I reconnect and try again, I get the exception shown at the bottom, it also hangs for quite a few seconds before spitting out the exception.

Code:

Dim myRequest As WebRequest = WebRequest.Create(http://www.google.com)

Dim myResponse As WebResponse

Try

myResponse = myRequest.GetResponse()

myResponse.Close()

Catch ex As WebException

message_textbox.Text = ex.ToString()

EndTry

Exception after trying to reconnect:

System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
--- End of inner exception stack trace ---
at System.Net.HttpWebRequest.GetResponse()

Something of a curiousity...When i first start up the program and hit the button to getwebresponse it hangs for a couple seconds like it's connecting, and then it will spit out "Can connect." If i press the button again, it will give me "Can connect" instantly without "trying" or hanging. Is it possible that it's keeping the connection alive even when I closed it?

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Visual Studio seems to say that myResponse was never opened in the first place. When I try to close it, in catch/finally it throws a NullReferenceException. And myResponse = Nothing didn't seem to help either.

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Nope, same response.

Have you set the timeout. If not, try doing that.

It basically works like this:
connect, then send data, wait for reply, disconnect

what's probably happening though is:
connect, fails, but still maintains the state of thinking it is connected or not connecting.

WebRequest.Timeout(1000) will throw an exception (handled by Try Catch) if it doesn't get a reply within 1 second, but the state should be reset. You might even want to set it up so that it retries a couple of times before displaying an error

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Ok I set the timeout at 1 second, and I did some testing.

Start the program

Hit the button

Get "The operation has timed out" Exception

Hit the button

Get "Connected"

Hit the button

Get "Connected"

Unplug the internet

Hit the button

Get "The operation has timed out" Exception

Hit the button

Get "The remote name could not be resolved" Exception

Plug the internet back in

Hit the button

Get "The operation has timed out" Exception

--From this point on it never shows the message "Connected" again.

Two other curiousities.

If I unplug the internet and then plug it back in without hitting the button it will stay "Connected."

If I unplug the internet and the only message I get is "The operation has timed out" and plug it back in and hit the button, I will get the "connected" message again.

It seems that if I ever see the message "The remote name could not be resolved" I never again receive the "Connected message."

That's kind of what I was thinking. Like the computer is keeping the state persistent and doesn't actually check for it. It goes something like "I've check this before, so there's no point in checking it again" I was hoping the timeout would tell it to check after 1 second.

The webrequest has an abort method, but not a dispose method. Setting something to Nothing usually accomplishes the same thing as a dispose (not exactly, but usually it's close enough). If it's an object that needs to be instantiated, you'll need to instantiate it again after a "= Nothing".

What about restarting the application?
Tried it on another computer?

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Thanks a lot for the consult Rob. When I tried the program on my laptop, it seemed to be working just fine. Not sure what was wrong with my work computer but I suppose it doesn't matter much. Must just be one of those things! Cheers :-)

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My vb code is supposed to send several variables to a server

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