Пример отправки широковещательного сообщения (API и MFC)

#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")

void wsaShowError();//Вывод сообщений о ошибках

int main()
{
 WSADATA wsaData;
 if(!WSAStartup(0x0202,&wsaData))
 {
 SOCKET SockBroad = socket(AF_INET,SOCK_DGRAM,0);
 if(SockBroad != INVALID_SOCKET)
 {
 BOOL bBroad = TRUE;
 if(!setsockopt(SockBroad,SOL_SOCKET,SO_BROADCAST,(char*)&bBroad,sizeof(BOOL)))
 {
 SOCKADDR_IN saUdp;
 saUdp.sin_family = AF_INET;
 saUdp.sin_addr.s_addr = htonl(INADDR_BROADCAST);
 saUdp.sin_port = htons(4004);
 char * szMessage ="Test Broadcast Message";
 if(sendto(SockBroad,szMessage,lstrlen(szMessage),0,(SOCKADDR*)&saUdp,sizeof(SOCKADDR_IN))
 != SOCKET_ERROR) 
 {
 closesocket(SockBroad);
 }else{wsaShowError();}
 }else{wsaShowError();}
 }else{wsaShowError();}
 }else{wsaShowError();}
 if(WSACleanup()){wsaShowError();}
 return 0;
}

void wsaShowError()
{
 LPVOID lpMsgBuf = NULL;
 FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
 NULL, WSAGetLastError(), 
 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 (LPTSTR) &lpMsgBuf, 0, NULL);
 MessageBox(NULL,(LPCTSTR)lpMsgBuf,"Error",MB_OK|MB_ICONSTOP);
 LocalFree(lpMsgBuf);
}

Пример создавался в Win32 Console Application, для работы программы необходимо в свойствах проекта(Alt+F7)
указать «Use MFC in a Shared DLL»

#include <afxsock.h>

int main()
{
 if(AfxSocketInit())
 {
 CSocket m_sock;
 if(m_sock.Create(3004,SOCK_DGRAM))
 {
 BOOL bBroadcast = TRUE;
 if(m_sock.SetSockOpt(SO_BROADCAST,&bBroadcast,sizeof(BOOL))!=SOCKET_ERROR)
 {
 CString m_message = "Test Broadcast Message";
 if(m_sock.SendTo(LPCTSTR(m_message),m_message.GetLength(),4004,NULL,0)==SOCKET_ERROR)
 {/*error*/}
 }else{/*error*/}
 m_sock.Close();
 }else{/*error*/}
 }else{/*error*/}
 return 0;
}