Using the Internet Transfer Control: Part 2

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When looking at the ErrorConstants, there are quite a lot. Well, don't worry, we don't need all of them. I have outlined the important ones below:

• icBadUrl
• icCannotConnect
• icConnectFailed
• icConnectionAborted
• icNoRemoteHost

Most of them are self explanatory, although I do want to point out one thing. The difference between icConnectFailed and icConnectionAborted is that icConnectionAborted shows that we were previously connected, but the remote host disconnected us.

Well, now that we have all these nice constants, how can we use them to detect and find out what's gone wrong?

You might have guessed that we need to work in the StateChanged event. We need to use the Select Case statement to detect the State, because it's a real pain to use lots of If statements:

Select Case State

  Case icError

    ' An error has occurred

End Select

A good way to find out what's going on is to use the Debug.Print method in the StateChanged event. For example, when using the code in the first part of the series to get a web page, you would see the following displayed in the Immediate window:

1
7
8
9
10

Uh?? What's all this? Am I supposed to memorize these numbers? No. The constants listed earlier with the numbers in brackets refer to these numbers. Here is what the numbers above translate to:

• 1 - icResolvingHost
• 7 - icReceivingResponse
• 8 - icResponseReceived
• 9 - icDisconnecting
• 10 - icDisconnected

As we can see the Inet control works fairly logically, first resolving the host name from the URL given, then getting a response and then disconnecting. If we provide an incorrect url, as in "http://" then we need to use standard error handling to pick up the error:

Private Function GetPage(strURL As String) As String

On Error Goto vbErrHand

' Code here

Exit Function

vbErrHand:

Msgbox Err.Description

End Function

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