delphi - 使用 "HNetCfg.NATUPnP"Ole对象进行端口转发失败

Question

我正在使用转发端口的代码。这段代码在我的 Windows 7 上运行良好；但我无法在 Windows XP 上使用它。

问题更新 1(2012-10-17 07:32:00Z)

这是我的源代码:

uses
  ActiveX, oleAuto;

Procedure AddUPnPEntry(Port: Integer; const Name: ShortString; LAN_IP: string);
Var
  Nat: Variant;
  Ports: Variant;
  SavedCW: Word;
Begin
  if NOT(LAN_IP = '127.0.0.1') then
  begin
    try
      Nat := CreateOleObject('HNetCfg.NATUPnP');
      Ports := Nat.StaticPortMappingCollection;

      // Error Raized From Here!!!
      ShowMessage(inttostr(Ports.count));

      Ports.Add(Port, 'TCP', Port, LAN_IP, True, name);
    except
      ShowMessage('An Error occured with adding UPnP Ports. The ' + name +
        ' port was not added to the router. Please check to see if  your ' +
        'router supports UPnP and has it enabled or disable UPnP.');
    end;
  end;
End;

procedure TForm1.Button2Click(Sender: TObject);
begin
  AddUPnPEntry(1234, 'Hello3', '192.168.1.1');
end;

AV 错误消息:

Project Project1.exe raised exception class $C0000005 with message 'access violation at 0x00504876: read of address 0x00000000'.

Answer 1

如果您在访问 count 属性时遇到访问冲突，这意味着 IStaticPortMappingCollection IUPnPNAT.get_StaticPortMappingCollection 返回的接口(interface)方法为nil，这可能是由于您的设备不支持 UPnP、设备上未启用 UPnP、未安装/激活 UPnP 用户界面等多种原因造成的。

无论如何，为了防止这种异常(访问冲突)，您必须在使用属性或方法之前检查它返回的值，在这种情况下您可以使用 VarIsClear功能如下:

try
  Nat := CreateOleObject('HNetCfg.NATUPnP');
  Ports := Nat.StaticPortMappingCollection;

  if not VarIsClear(Ports) then
  begin
    //do something
    ShowMessage(inttostr(Ports.count));
    Ports.Add(Port, 'TCP', Port, LAN_IP, True, name);
  end;

except on E:Exception do
  ShowMessage('An Error occured with adding UPnP Ports. '+E.Message);
end;