类中出现struct UPnPError : std::exception {};这句啥意思，怎么有“：”的

[图灵转世]

class CUPnPImpl
{
public:
CUPnPImpl();
virtual ~CUPnPImpl();
struct UPnPError : std::exception {};
enum {
UPNP_OK,
UPNP_FAILED,
UPNP_TIMEOUT
};

virtual void StartDiscovery(uint16 nTCPPort, uint16 nUDPPort, uint16 nTCPWebPort) = 0;
virtual bool CheckAndRefresh() = 0;
virtual void StopAsyncFind() = 0;
virtual void DeletePorts() = 0;
virtual bool IsReady() = 0;
virtual int GetImplementationID() = 0;

void LateEnableWebServerPort(uint16 nPort); // Add Webserverport on already installed portmapping

void SetMessageOnResult(HWND hWindow, UINT nMessageID);
TRISTATE ArePortsForwarded() const { return m_bUPnPPortsForwarded; }
uint16 GetUsedTCPPort() { return m_nTCPPort; }
uint16 GetUsedUDPPort() { return m_nUDPPort; }

// Implementation
protected:
volatile TRISTATE m_bUPnPPortsForwarded;
void SendResultMessage();
uint16 m_nUDPPort;
uint16 m_nTCPPort;
uint16 m_nTCPWebPort;
bool m_bCheckAndRefresh;

private:
HWND m_hResultMessageWindow;
UINT m_nResultMessageID;

};

[Eleven]

private 继承