IP多播技术及其编程(4)

// CMulticastSocketDlg.cpp : 实现文件 
#include "stdafx.h" 
#include "winsock2.h" 
#include "CMulticastSocket.h" 
#include "CMulticastSocketDlg.h" 
…… 
DWORD cbRet; 
SOCKET Sock,SockM; file://UDP套接字，多播套接字 
BOOL bFlag,bJoin; 
SOCKADDR_IN local,Remote,From; file://分别指向本地、多播组和数据来源的IP地址与端口 
int Fromlen; 
char ReceiveBuf[32000]; file://接收缓冲区 
BOOL bDataReceived; 
…… 
BEGIN_MESSAGE_MAP(CCMulticastSocketDlg, CDialog) 
…… 
ON_BN_CLICKED(IDC_JOIN_BUTTON, OnBnClickedJoinButton) 
ON_BN_CLICKED(IDC_LEAVE_BUTTON, OnBnClickedLeaveButton) 
ON_BN_CLICKED(IDC_QUIT_BUTTON, OnBnClickedQuitButton) 
ON_BN_CLICKED(IDC_SEND_BUTTON, OnBnClickedSendButton) 
ON_WM_TIMER() 
ON_MESSAGE(WM_SOCK_MSG,OnSocketMsg) 
END_MESSAGE_MAP() 

BOOL CCMulticastSocketDlg::OnInitDialog() 
{ 
CDialog::OnInitDialog(); 
…… 
SetTimer(1,100,NULL); file://设置定时器 
Fromlen=sizeof(From); 
bDataReceived=TRUE; 
bJoin=FALSE; 
return TRUE; // 除非设置了控件的焦点，否则返回 TRUE 
} 
…… 
void CCMulticastSocketDlg::OnBnClickedJoinButton() file://加入多播组 
{ 
if(m_JoinDlg.DoModal()==IDOK) 
{ 
WORD wVersionRequested; 
WSADATA wsaData; 
int 北京中庆; 
wVersionRequested = MAKEWORD(2,2); 
北京中庆 = WSAStartup(wVersionRequested, &wsaData); file://初始化WinSock2资源 
if(北京中庆!= 0){ 
AfxMessageBox("不能加载Windows套接字动态链接库,MB_OK"); 
return; 
} 
if (LOBYTE(wsaData.wVersion) !=2 || HIBYTE(wsaData.wVersion) !=2){ 
AfxMessageBox("WinSock DLL不支持2.0版本,MB_OK"); 
WSACleanup( ); 
return; 
} 
file://创建一个套接字 
Sock=WSASocket(AF_INET,SOCK_DGRAM,IPPROTO_UDP, 
(LPWSAPROTOCOL_INFO)NULL,0,WSA_FLAG_OVERLAPPED 
| WSA_FLAG_MULTIPOINT_C_LEAF|WSA_FLAG_MULTIPOINT_D_LEAF); 

bFlag=TRUE; file://设置套接字选项，使套接字为可重用端口地址 
setsockopt(Sock,SOL_SOCKET,SO_REUSEADDR,(char*)&bFlag,sizeof(bFlag)); 

file://将套接字绑定到用户指定端口及默认的接口 
memset(&local,0,sizeof(local)); 
local.sin_family=AF_INET; 
local.sin_port=htons((USHORT)m_JoinDlg.m_nPort); 
local.sin_addr.s_addr=htonl(INADDR_ANY); 
bind(Sock,(struct sockaddr FAR *)&local,sizeof(local)); 

file://设置多播数据报传播范围（生存时间TTL） 
WSAIoctl(Sock,SIO_MULTICAST_SCOPE,&m_JoinDlg.m_nTTL,sizeof(int), 
NULL,0,&cbRet,NULL,NULL); 
file://设置多播返回（LOOKBACK） 
BOOL nLoopBack=m_JoinDlg.m_Loopback; 
WSAIoctl(Sock,SIO_MULTIPOINT_LOOPBACK,&nLoopBack,sizeof(nLoopBack), 
NULL,0,&cbRet,NULL,NULL); 

memset(&Remote,0,sizeof(Remote)); 
Remote.sin_family=AF_INET; 
Remote.sin_addr.s_addr=inet_addr(m_JoinDlg.m_IPAddress); 
Remote.sin_port=htons(m_JoinDlg.m_nPort); 
file://加入到指定的多播组，并指定为既作为发送者又作为接收者（JL_BOTH） 
SockM=WSAJoinLeaf(Sock,(sockaddr*)&Remote,sizeof(Remote), 
NULL,NULL,NULL,NULL,JL_BOTH); 
WSAAsyncSelect(Sock,m_hWnd,WM_SOCK_MSG,FD_READ); file://注册网络消息及其网络事件 
bJoin=TRUE; 
} 
} 

void CCMulticastSocketDlg::OnBnClickedSendButton() file://多播发送 
{ 
if(bJoin){ 
UpdateData(TRUE); 
const char* strMessage=LPCTSTR(m_SendMessage); 
int nSize=m_SendMessage.GetLength()+1; 
sendto(Sock,strMessage,nSize,0,(sockaddr*)&Remote,sizeof(Remote)); 
} 
else 
AfxMessageBox("请先加入多播组！"); 
m_SendMessage=""; 
UpdateData(FALSE); 
} 

void CCMulticastSocketDlg::OnBnClickedLeaveButton() 
{ file://离开多播组 
closesocket(SockM); 
closesocket(Sock); 
WSACleanup(); 
m_SendMessage=""; 
m_ReceiveMessage=""; 
bDataReceived=TRUE; 
bJoin=FALSE; 
UpdateData(FALSE); 
} 

void CCMulticastSocketDlg::OnBnClickedQuitButton() 
{ file://退出 
DestroyWindow(); 
} 

void CCMulticastSocketDlg::OnTimer(UINT nIDEvent) 
file://定时器处理函数，实现接收信息的定时更新 
{ 
if(bDataReceived) 
{ 
m_ReceiveMessage+=ReceiveBuf; 
m_ReceiveMessage+="\r\n"; 
bDataReceived=FALSE; 
UpdateData(FALSE); 
} 
CDialog::OnTimer(nIDEvent); 
} 

LRESULT CCMulticastSocketDlg::OnSocketMsg(WPARAM wParam,LPARAM lParam) 
{ 
file://检索网络事件 
switch(WSAGETSELECTEVENT(lParam)){ 
case FD_READ: 
recvfrom(Sock,ReceiveBuf,32000,0,(sockaddr *)&From,&Fromlen); 
bDataReceived=TRUE; file://设置已接收到一条信息标志 
break; 
} 
return TRUE; 
}