用Visual C++实现局域网IP多播

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
#define MCASTADDR "233.0.0.1" //本例使用的多播组地址。
#define MCASTPORT 5150 //绑定的本地端口号。
#define BUFSIZE 1024 //接收数据缓冲大小。
int main( int argc,char ** argv)
{
　WSADATA wsd;
　struct sockaddr_in local,remote,from;
　SOCKET sock,sockM;
　TCHAR recvbuf[BUFSIZE];
　/*struct ip_mreq mcast; // Winsock1.0 */
　int len = sizeof( struct sockaddr_in);
　int ret;
　//初始化WinSock2.2
　if( WSAStartup( MAKEWORD(2,2),&wsd) != 0 )
　{
printf("WSAStartup() failed\n");
return -1;
　}
　/*
　创建一个SOCK_DGRAM类型的SOCKET
　其中,WSA_FLAG_MULTIPOINT_C_LEAF表示IP多播在控制面层上属于"无根"类型;
　WSA_FLAG_MULTIPOINT_D_LEAF表示IP多播在数据面层上属于"无根",有关控制面层和
　数据面层有关概念请参阅MSDN说明。
　*/
　if((sock=WSASocket(AF_INET,SOCK_DGRAM,0,NULL,0,
WSA_FLAG_MULTIPOINT_C_LEAF|WSA_FLAG_MULTIPOINT_D_LEAF|
WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)
　{
printf("socket failed with:%d\n",WSAGetLastError());
WSACleanup();
return -1;
　}
　//将sock绑定到本机某端口上。
　local.sin_family = AF_INET;
　local.sin_port = htons(MCASTPORT);
　local.sin_addr.s_addr = INADDR_ANY;
　if( bind(sock,(struct sockaddr*)&local,sizeof(local)) == SOCKET_ERROR )
　{
printf( "bind failed with:%d \n",WSAGetLastError());
closesocket(sock);
WSACleanup();
return -1;
　}
　//加入多播组
　remote.sin_family = AF_INET;
　remote.sin_port = htons(MCASTPORT);
　remote.sin_addr.s_addr = inet_addr( MCASTADDR );
　/* Winsock1.0 */
　/*
　mcast.imr_multiaddr.s_addr = inet_addr(MCASTADDR);
　mcast.imr_interface.s_addr = INADDR_ANY;
　if( setsockopt(sockM,IPPROTO_IP,IP_ADD_MEMBERSHIP,
(char*)&mcast,sizeof(mcast)) == SOCKET_ERROR)
　{
printf("setsockopt(IP_ADD_MEMBERSHIP) failed:%d\n",WSAGetLastError());
closesocket(sockM);
WSACleanup();
return -1;
　}
　*/
　/* Winsock2.0*/
　if(( sockM = WSAJoinLeaf(sock,(SOCKADDR*)&remote,sizeof(remote),
NULL,NULL,NULL,NULL,
JL_BOTH)) == INVALID_SOCKET)
　{
printf("WSAJoinLeaf() failed:%d\n",WSAGetLastError());
closesocket(sock);
WSACleanup();
return -1;
　}
　//接收多播数据，当接收到的数据为"QUIT"时退出。
　while(1)
　{
if(( ret = recvfrom(sock,recvbuf,BUFSIZE,0,
(struct sockaddr*)&from,&len)) == SOCKET_ERROR)
{
　printf("recvfrom failed with:%d\n",WSAGetLastError());
　closesocket(sockM);
　closesocket(sock);
　WSACleanup();
　return -1;
}
if( strcmp(recvbuf,"QUIT") == 0 ) break;
else {
　recvbuf[ret] = '\0';
　printf("RECV:' %s ' FROM <%s> \n",recvbuf,inet_ntoa(from.sin_addr));
}
　}
　closesocket(sockM);
　closesocket(sock);
　WSACleanup();
　return 0;
}