// broadcast message SEND.cpp
// ルーターは通常超えられません。
// 同期モード

WSADATA m_wsaData;
BOOL yes = 1;

if (WSAStartup(MAKEWORD(1, 1), &m_wsaData) != 0) MessageBox("fail to TCP start\n");
m_s = socket(AF_INET, SOCK_DGRAM, 0);

addr.sin_family = AF_INET;
addr.sin_port = htons(12345);
addr.sin_addr.s_addr = inet_addr("255.255.255.255");

setsockopt(m_s,  SOL_SOCKET, SO_BROADCAST, (char *)&yes, sizeof(yes));

// SEND
CString ss;
GetDlgItemText(IDC_EDIT1,ss);

sendto(m_s, ss,ss.GetLength(), 0, (struct sockaddr *)&addr, sizeof(addr));

--------------------------------------------------------------------------------------------------


// broadcast message RECV.cpp
void CRecDlg::rec(){
	 
	WSAData wsaData;
	SOCKET sock;
	struct sockaddr_in addr;
	char buf[2048];

	WSAStartup(MAKEWORD(2,0), &wsaData);
	
	sock = socket(AF_INET, SOCK_DGRAM, 0);
	addr.sin_family = AF_INET;
	addr.sin_port = htons(12345);
	addr.sin_addr.S_un.S_addr = INADDR_ANY;

	bind(sock, (struct sockaddr *)&addr, sizeof(addr));
	
	memset(buf, 0, sizeof(buf));
	while (1){ 
		recv(sock, buf, sizeof(buf), 0);
		if ( buf[0] == '0' ) 
			break;
		else {
			AfxMessageBox (buf);
			memset(buf, 0, sizeof(buf));
		}
	}

	 closesocket(sock);
	 WSACleanup();
}