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