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 //本地端口号。
#define BUFSIZE 1024 //发送数据缓冲大小。
int main( int argc,char ** argv)
{
　WSADATA wsd;
　struct sockaddr_in remote;
　SOCKET sock,sockM;
　TCHAR sendbuf[BUFSIZE];
　int len = sizeof( struct sockaddr_in);
　//初始化WinSock2.2
　if( WSAStartup( MAKEWORD(2,2),&wsd) != 0 )
　{
printf("WSAStartup() failed\n");
return -1;
　}
　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;
　}
　//加入多播组
　remote.sin_family = AF_INET;
　remote.sin_port = htons(MCASTPORT);
　remote.sin_addr.s_addr = inet_addr( MCASTADDR );
　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;
　}
　//发送多播数据，当用户在控制台输入"QUIT"时退出。
　while(1)
　{
printf("SEND : ");
scanf("%s",sendbuf);
if( sendto(sockM,(char*)sendbuf,strlen(sendbuf),0,
(struct sockaddr*)&remote,sizeof(remote))==SOCKET_ERROR)
{
　printf("sendto failed with: %d\n",WSAGetLastError());
　closesocket(sockM);
　closesocket(sock);
　WSACleanup();
　return -1;
}
if(strcmp(sendbuf,"QUIT")==0) break;
Sleep(500);
　}
　closesocket(sockM);
　closesocket(sock);
　WSACleanup();
　return 0;
}