In IIS8 we introduced a new interface and associated API's to handle Websocket requests. IWebSocketContext.

Setup: To get this functionality working, Web Socket Protocol module should be enabled in the IIS features.

Runtime: If a incoming request is to be accepted as a Websocket request and subsequently upgraded, the handler must set the response status as 101. It should initiate a IHttpResponse->Flush, which will trigger the IIS Websocket module to do the necessary work to send out the 101 response to the client.

Once the response is sent, the handler can get a pointer to the IWebSocketContext through the IHttpContext3's GetNamedContext API.

The IWebSocketContext API exposes the necessary API's to read / write Websocket data.

Sample Code to get pointer to IWebSocketContext:

    //
    // Get Pointer to the IHttpContext3
    //

    hr = HttpGetExtendedInterface( g_pServerInfo, pHttpContext, &pHttpContext3 );
    if ( FAILED ( hr ) )
    {
        goto Finished;
    }

    //
    // Get Pointer to IWebSocketContext
    //

    _pWebSocketContext = (IWebSocketContext *)pHttpContext3->GetNamedContextContainer()->GetNamedContext("websockets");

    if ( _pWebSocketContext == NULL )
    {
        hr = HRESULT_FROM_WIN32( ERROR_FILE_NOT_FOUND );
        goto Finished;
    }

Reference

RFC http://www.rfc-editor.org/rfc/rfc6455.txt

IWebSocketContext:: http://msdn.microsoft.com/en-us/library/hh852804(v=vs.90).aspx

IHttpContext3: http://msdn.microsoft.com/en-us/library/hh852784(v=vs.90