COM组件中客户程序向服务器程序注册失败的原因？

[shao]

在客户程序接收器调用服务器接口IConnectionPoint的Advise()向服务器注册时总是失败（拒绝访问），而调用接口IConnectionPoint的其他几个函数时均可成功。而且在本机运行时也可注册成功，在远程调用时出现上述问题。请问如何解决？

[mach]

试试在你的客户机上设置权限,因为服务端要通过你Advise提供的接口调用客护端.

[huitor]

请查阅微软的bug报告。
Note that both Microsoft Foundation Classes (MFC) and Active Template Library (ATL) have bugs in their IConnectionPoint::Advise implementation. They both do essentially the following:


HRESULT CConnectionPoint::Advise(IUnknown* pUnkSink, DWORD *pdwCookie)
{
IUnknown* p;
HRESULT hRes = S_OK;
if (SUCCEEDED(pUnkSink->QueryInterface(*m_piid, (void**)&p)))
{
// Add p to the list of sinks;
}
else
{
hRes = CONNECT_E_CANNOTCONNECT; // ATL does this
hRes = E_NOINTERFACE; // MFC does this
}
return hRes;
}


The bug is that they should return whatever the QI call returned instead of mapping to CONNECT_E_CANNOTCONNECT or E_NOINTERFACE. The correct way to implement a connection point is roughly the following:

HRESULT CConnectionPoint::Advise(IUnknown* pUnkSink, DWORD *pdwCookie)
{
IUnknown* p;
HRESULT hRes = pUnkSink->QueryInterface(*m_piid, (void**)&p);
if (SUCCEEDED(hRes))
{
// Add p to the list of sinks, maybe returning
// CONNECT_E_ADVISELIMIT if necessary
}
else if (hRes == E_NOINTERFACE)
{
// The sink does not support *m_piid!
return CONNECT_E_CANNOTCONNECT;
}
return hRes;
}