- 组播:
过多的广播
会占用网络带宽
,产生广播风暴
的现象,从而影响正常的通信
活动;组播
(或者多播
)是局域网内部
的通信,只有加入到某个多播组
的主机才能收到数据;- 组播的方式既可以发给多个主机,又能避免广播带来过多的网络负载;
- 组播地址:D类地址:“
224.0.0.1~239.255.255.254
”; - 设置组播的流程:
- 发送方(UDP的客户端):
- 一、创建用户数据报套接字(socket函数):
int sockfd = socket(AF_INET,SOCK_DGRAM,0);if(-1 == sockfd){perror("socket error");exit(-1);}
- 二、填充组播信息结构体( struct sockaddr_in):
struct sockaddr_in serveraddr;socklen_t serveraddr_len = sizeof(serveraddr);memset(&serveraddr,0,serveraddr_len);serveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(M_IP);serveraddr.sin_port = htons(PORT);
char buf[128] = {0};while(true){memset(buf,0,sizeof(buf));fgets(buf,128,stdin);buf[strlen(buf)-1] = '\0';if(!strncmp(buf,"quit",4)){break;}if(-1 == (sendto(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&serveraddr,serveraddr_len))){perror("sendto error");exit(-1);}}
close(sockfd);
- 接收方(UDP的服务器):
- 一、创建用户数据报套接字(socket函数):
int sockfd = socket(AF_INET,SOCK_DGRAM,0);if(-1 == sockfd){perror("socket error");exit(-1);}
- 二、填充组播信息结构体(struct sockaddr_in):
struct sockaddr_in serveraddr,clientaddr;socklen_t serveraddr_len = sizeof(serveraddr);socklen_t clientaddr_len = sizeof(clientaddr);memset(&serveraddr,0,serveraddr_len);serveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(M_IP);serveraddr.sin_port = htons(PORT);
- 三、用户数据报套接字和广播信息结构体绑定(bind函数):
if(-1 == (bind(sockfd,(struct sockaddr *)&serveraddr,serveraddr_len))){perror("bind error");exit(-1);}
struct ip_mreqn {struct in_addr imr_multiaddr; struct in_addr imr_address; int imr_ifindex; };struct ip_mreqn multi_group;multi_group.imr_address.s_addr = INADDR_ANY;multi_group.imr_multiaddr.s_addr = inet_addr(M_IP);multi_group.imr_ifindex = 0;if(-1 == (setsockopt(sockfd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&multi_group,sizeof(multi_group)))){perror("setsockopt error");exit(-1);}
char buf[128] = {0};while(true){memset(buf,0,sizeof(buf));if(-1 == recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr *)&clientaddr,&clientaddr_len)){perror("recvfrom error");exit(-1);}printf("客户端[%s:%d]发来数据[%s]\n",inet_ntoa(clientaddr.sin_addr),ntohs(clientaddr.sin_port),buf);}
close(sockfd);