====== How Can I Determine, If The TCP Connection Is Still Active? ======

Direct testing is impossible. Determining if a connection is still alive can only be done at the moment of communicating. If you try to send or receive data on a broken TCP channel, then an error is returned. This is the only way to test for a broken TCP channel! There are not any event what can be raised when connection was broken.

If connection is closed gracefully, then CanRead is signalled, but the read operation reads 0 bytes.

Yes, other packages have an 'active' property, but the true value of this property is determined using the previous principles. It is not a direct determination of the live TCP connection status. It is a faked value!

To determinate if FTP connection is still alive you can use that function:

<code delphi>
function CheckFtpConnection(AFtpSend: TFtpSend): Boolean;
begin
  if AFtpSend.Sock.Socket = NOT(0) then // Check if socked was ever opened
    Result := AFtpSend.Login            // If not, then connect and login to FTP
  else
    if AFtpSend.NoOp then               // Send NOOP (No Operation) FTP command to check FTP connection
      Result := True                    // If it response without error then connection works fine
    else
      Result := AFtpSend.Login;         // If fails (for some reasos, timeout, etc), then connect and login to FTP
end;

//[...]

procedure TForm1.Button1Click(Sender: TObject)
begin
  if not CheckFtpConnection(FtpSend) then // Check if connection works fine, if not then it will reconnect as needed
  begin
    ShowMessage('Connection to FTP failed!');
    Exit;
  end;
  // Do FTP action(s)
  //[...]
  if FtpSend.List('/', False) then
  //[...]
end;
</code>