How to test if client is dropped (tcp/ip)

Should tcp/ip connection notice automaticly if client drops out when the computers network cable got detached or dialup-internet connection was lost.
  My server should be able to test these hanging dead connections, because when the user reconnects it's username is already used in a hanging dead connection.
  Is there a call in tcp/ip routines that could verify working connection without changing client or server by adding a ping routine.
  I'm using Francois Piette's tcp/ip component ( in delphi 1.2

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intheConnect With a Mentor Commented:
as far as im aware you will have to ping to check
as tcp/ip is only a protocol i dont see how its going to know when connection is dropped.pinging is always the safest way to check.
same as for testing if internet connection exists.
if you can use wininet in d1 then something like this could help:

procedure TForm1.Button1Click(Sender: TObject);
   dwConnectionTypes: dWord;
dwConnectionTypes := 0;
if InternetGetConnectedState(@dwConnectionTypes, 0) then
  showmessage('not connected');

check teh sources of some of he online components,maybe one of them works in d1 or you can use sources ofit. may have something useful.
Regards Barry
when i say online componenst ,i mean caus ei got a componet called tonline thtas can tell if im onine or not by using ras api,it checks if a dialup connection has been made or not but it says for d2 and up so doubt it works on d1
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