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Am I connected to the Internet?

Posted on 2002-03-26
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Last Modified: 2010-04-04
Using Delphi 3...

How can my D3 application detect whether the user is currently connected to the Internet or not?
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Question by:Kapusta
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3 Comments
 
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Expert Comment

by:Stuart_Johnson
ID: 6897994
What type of D3 are you using?  Developer / Profession / Client Server?  Do you have any internet controls?

Stu
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Author Comment

by:Kapusta
ID: 6898013
I am using Delphi Professional.  As far as components, I have the Internet Mail Suite 1.x by Artchil Gogava.
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Stuart_Johnson earned 200 total points
ID: 6898103
Hi Kapusta,

Here is some code for you.

const
  INTERNET_CONNECTION_MODEM           = 1;
  INTERNET_CONNECTION_LAN             = 2;
  INTERNET_CONNECTION_PROXY           = 4;
  INTERNET_CONNECTION_MODEM_BUSY      = 8;

function InternetGetConnectedState(lpdwFlags: LPDWORD;
  dwReserved: DWORD): BOOL; stdcall; external 'WININET.DLL';

function  _IsConnectedToInternet: Boolean;
var
  dwConnectionTypes: Integer;
begin
  try
    dwConnectionTypes := {INTERNET_CONNECTION_MODEM +}
                         INTERNET_CONNECTION_LAN +
                         INTERNET_CONNECTION_PROXY;
    if InternetGetConnectedState(@dwConnectionTypes, 0) then
      Result := true
    else
      Result := false;
  except
    Result := false;
  end;
end;



procedure TForm1.Button1Click(Sender: TObject);
begin
   if _IsConnectedToInternet then
     ShowMessage('Yes')
   else
     ShowMessage('No');
end;

This works fine, however it doesn't detect an instant disconnect/connect.  I've found I have to retry it a couple of times before it realises that you're no longer connected to the net (this is the case with Lan anyway, not sure about modem).  This is a Windows thing, not a Delphi/Code thing.

Let me know if you need anymore help,

Cheers,

Stu
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