需包含头文件<sys/socket.h>
socket(AF_INET,SOCK_DGRAM,0)
setsockopt(fd,sol)
struct sockaddr_in addr;
int fd;
u_int yes=1; /*** MODIFICATION TO ORIGINAL */
/* create what looks like an ordinary UDP socket */
if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)
{
perror("socket");
exit(1);
}
if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0)
{
perror("Reusing ADDR failed");
exit(1);
}
/*** END OF MODIFICATION TO ORIGINAL */
/* set up destination address */
memset(&addr,0,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=htonl(INADDR_ANY); /* N.B.: differs from sender */
addr.sin_port=htons(dwport);
/* bind to receive address */
if (bind(fd,(struct sockaddr *) &addr,sizeof(addr)) < 0)
{
perror("bind");
exit(1);
}
/* use setsockopt() to request that the kernel join a multicast group */
mreq.imr_multiaddr.s_addr=inet_addr(szMultiAddr);
mreq.imr_interface.s_addr=inet_addr(szLocalIP);//htonl(INADDR_ANY);
if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0)
{
printf("setsockopt multi error ");
exit(1);
}
fd_set set ; int handle; struct timeval tv; FD_ZERO(&set); FD_SET(handle,&set); tv.tv_sec =5 select(fd+1,&set,NULL,NULL,tv); nret =FD_ISSET(handle,&set); if(nret>0) receive data;
select与epoll区别
1.select支持1024个文件描述符，采用轮询文件描述符，看是否有可读或者可写的数据。epoll采用回调机制实现，适用于大规模并发。
2.select需要将文件句柄从内核空间拷贝到用户空间，造成资源浪费，并且需要遍历整个数组才能知道那个句柄发生了事件。
3.epoll只返回发生事件的句柄和数量，相对要高效很多