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POCoCreateInstance hangs in single-threaded exe COM client
 

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  1. POCoCreateInstance hangs in single-threaded exe COM client
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    <p>I'm learning the basics of COM. Right now I'm writing out-of-process server. I wrote pretty basic server app, dll/stub and client app. </p> <p>If I register server and create an instance of an object using CoCreateInstance in-process, it works:</p> <p><strong>SERVER/CLIENT:</strong></p> <pre><code>int _tmain(int argc, _TCHAR* argv[]) { IClassFactory *factory = new ISimpleServerFactory(); DWORD classToken; ::CoInitialize(NULL); CoRegisterClassObject( IID_ISimpleServer, factory, CLSCTX_LOCAL_SERVER, REGCLS_MULTIPLEUSE, &amp;classToken); ISimpleServer *pISimpleServer = NULL; HRESULT hr = CoCreateInstance( CLSID_CSimpleServer, NULL, CLSCTX_LOCAL_SERVER, IID_ISimpleServer, (void **)&amp;pISimpleServer); //&lt;===========SUCCESS if(SUCCEEDED(hr)) printf("Instantiation successful\n"); if(pISimpleServer != NULL) pISimpleServer-&gt;Release(); std::cin.ignore(); CoRevokeClassObject(classToken); ::CoUninitialize(); return 0; } </code></pre> <p>Now I try splitting it into separate apps:</p> <p><strong>SERVER:</strong></p> <pre><code>int _tmain(int argc, _TCHAR* argv[]) { IClassFactory *factory = new ISimpleServerFactory(); DWORD classToken; ::CoInitialize(NULL); CoRegisterClassObject( IID_ISimpleServer, factory, CLSCTX_LOCAL_SERVER, REGCLS_MULTIPLEUSE, &amp;classToken); if(SUCCEEDED(hr)) printf("Instantiation successful\n"); if(pISimpleServer != NULL) pISimpleServer-&gt;Release(); std::cin.ignore(); CoRevokeClassObject(classToken); ::CoUninitialize(); return 0; } </code></pre> <p><strong>CLIENT:</strong></p> <pre><code>int _tmain(int argc, _TCHAR* argv[]) { CoInitialize(NULL); SimpleServer::ISimpleServer *pISimpleServer = NULL; HRESULT hr = CoCreateInstance( CLSID_CSimpleServer, NULL, CLSCTX_LOCAL_SERVER, IID_ISimpleServer, (void **)&amp;pISimpleServer); // HERE IT HANGS if (SUCCEEDED(hr)) { //*****SMTH*** } else { printf("Failed to load COM object (server not loaded?)\n"); } if(pISimpleServer != NULL) pISimpleServer-&gt;Release(); CoUninitialize(); std::cin.ignore(); return 0; } </code></pre> <p>And client hangs on run. If server is not launched, client types "Failed to load COM object (server not loaded?)", so I suppose it's not a problem of server registration.</p> <p>But what could it be then?</p>
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    1. USGaro Robe
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    1. COYour server is not pumping messages.
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      1. POCoCreateInstance hangs in single-threaded exe COM client
      1. USRaymond Chen
    2. COAnd what does it mean?
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      1. POCoCreateInstance hangs in single-threaded exe COM client
      1. USGaro Robe
    3. COA thread running in a single-threaded apartment (which is what you joined when you called `::CoInitialize(NULL)`) must never block, but must instead run a message pump - that is, call `GetMessage` and `DispatchMessage` (at least) in a loop. Incoming cross-apartment COM calls are sent to an STA thread in the form of window messages, which said thread must retrieve and process.
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      1. POCoCreateInstance hangs in single-threaded exe COM client
      1. USIgor Tandetnik
 

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