ot;, &client.sin_addr.s_addr);
int cnt = 0;
while(1){
char buf[64] = {0};
sprintf(buf, "count=%d", cnt++);
int ret = sendto(fd, buf, sizeof buf, 0, (struct sockaddr*)&client, sizeof(client));
if(ret == -1){
perror("sendto -1");
}
sleep(1);
}
}
注意点:
必须用setsockopt函数开通套接字的组播权限。发送端使用IPPROTO_IP和IP_MULTICAST_IF
函数if_nametoindex的作用是通过网卡的名字,取得网卡的mac地址。
组播接收端例子
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <net/if.h>
int main(int agrc, char** argv){
int fd = socket(AF_INET, SOCK_DGRAM, 0);
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(6666);
//addr.sin_addr.s_addr = htons(INADDR_ANY);
inet_pton(AF_INET, "0.0.0.0", &addr.sin_addr.s_addr);
socklen_t len = sizeof(addr);
bind(fd, (struct sockaddr*)&addr, sizeof(addr));
struct ip_mreqn n;
inet_pton(AF_INET, "239.0.0.10", &n.imr_multiaddr.s_addr);
inet_pton(AF_INET, "0.0.0.0", &n.imr_address.s_addr);
n.imr_ifindex = if_nametoindex("enp0s3");
int ret = setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
&n, sizeof(n));
while(1){
char buf[64] = {0};
int ret = recvfrom(fd, buf, sizeof(buf), 0, NULL, NULL);
write(STDOUT_FILENO, buf, ret);
sleep(1);
}
}
注意点:
必须用setsockopt函数把接收端的套接字加入到组播的组里。接收端使用IPPROTO_IP和IP_ADD_MEMBERSHIP
由于组播的时候,必须指定接收端的端口号,所以接收端必须调用bind函数,显示的指定自己用的端口号
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