Zero Configuration Networking: The Definitive Guide

7.6. Event Handling with Microsoft Windows MFC

If you're programming using the Microsoft Windows MFC (Microsoft Foundation Classes) programming model, then you don't need your own event loop. You just declare the messages that your window accepts, and, as events happen, MFC sends the appropriate message to your window object. Example 7-10 shows an outline of what you need to do to integrate (in this example) DNS-SD browsing into an MFC application.

Example 7-10. Windows MFC example

#include "stdafx.h" #include <dns_sd.h> #include <winsock2.h> #define WM_PRIVATE_SERVICE_EVENT ( WM_USER + 0x100 ) class MyWindow : public CWnd { public: MyWindow( ); virtual ~MyWindow( void ); protected: // General afx_msg int OnCreate( LPCREATESTRUCT inCreateStruct ); afx_msg void OnDestroy( void ); afx_msg LONG OnServiceEvent( WPARAM inWParam, LPARAM inLParam ); // Browsing static void DNSSD_API BrowseReply( DNSServiceRef inRef, DNSServiceFlags inFlags, uint32_t inInterfaceIndex, DNSServiceErrorType inErrorCode, const char * inName, const char * inType, const char * inDomain, void * inContext ); DECLARE_MESSAGE_MAP( ) private: DNSServiceRef m_serviceRef; }; BEGIN_MESSAGE_MAP( MyWindow, CWnd ) ON_WM_CREATE( ) ON_WM_DESTROY( ) ON_MESSAGE( WM_PRIVATE_SERVICE_EVENT, OnServiceEvent ) END_MESSAGE_MAP( ) int MyWindow::OnCreate( LPCREATESTRUCT inCreateStruct ) { DNSServiceErrorType err; err = CWnd::OnCreate( inCreateStruct ); if ( err ) goto exit; err = DNSServiceBrowse( &m_serviceRef, 0, 0, "_http._tcp", NULL, BrowseReply, this ); if ( err ) goto exit; err = WSAAsyncSelect( (SOCKET) DNSServiceRefSockFD(m_serviceRef), m_hWnd, WM_PRIVATE_SERVICE_EVENT, FD_READ|FD_CLOSE); exit: if ( err ) { if ( m_serviceRef ) { DNSServiceRefDeallocate( m_serviceRef ); m_serviceRef = NULL; } } return( err ); } void MyWindow::OnDestroy( void ) { // ... if ( m_serviceRef ) { WSAAsyncSelect( ( SOCKET ) DNSServiceRefSockFD( m_serviceRef ), m_hWnd, 0, 0 ); DNSServiceRefDeallocate( m_serviceRef ); } // ... } LONG MyWindow::OnServiceEvent(WPARAM inWParam, LPARAM inLParam) { SOCKET sock = (SOCKET) inWParam; DNSServiceErrorType err; if ( WSAGETSELECTERROR(inLParam) && !(HIWORD(inLParam))) goto exit; ASSERT( ( SOCKET ) DNSServiceRefSockFD( m_serviceRef ) == sock ); err = DNSServiceProcessResult( m_serviceRef ); ASSERT( !err ); exit: return ( 0 ); } void DNSSD_API MyWindow::BrowseReply( DNSServiceRef inRef, DNSServiceFlags inFlags, uint32_t inInterfaceIndex, DNSServiceErrorType inErrorCode, const char * inName, const char * inType, const char * inDomain, void * inContext ) { MyWindow * self = reinterpret_cast<MyWindow*>( inContext ); ASSERT( self ); // ... }