Can UDP multicast sucess while offline？ - c

Question

a demo about UDP multicast,when i want to test if the code is right, I found failed ,but i think is not the problem of the code.My virtual machine is offline,so i think whether is udp cannot multicast when the machine is offline?
this is my code:
//this is for receive
int main(int argc,char **argv) //My Multicast address is 224.0.0.88
{
int udpsocket;
int res;
char buf[50];
struct sockaddr_in saddr;
struct sockaddr_in raddr;
bzero(&saddr,sizeof(saddr));
bzero(&raddr,sizeof(raddr));
// 初始化地址结构体变量
saddr.sin_family = AF_INET;
saddr.sin_port = htons(5001);
saddr.sin_addr.s_addr = htonl(INADDR_ANY);
// 定义并初始化组播的结构体
struct ip_mreq mreq;
bzero(&mreq, sizeof mreq);
mreq.imr_multiaddr.s_addr = inet_addr(argv[1]); //组播地址，D类型
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
// 创建udp套接字
udpsocket = socket(AF_INET,SOCK_DGRAM,0);
if(udpsocket == -1)
{
perror("create udp socket failed!\n");
return -1;
}
// 设置可以组播
setsockopt(udpsocket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
&mreq, sizeof mreq);
int ret = sizeof(struct sockaddr);
// 绑定
res = bind(udpsocket,(struct sockaddr *)&saddr,ret);
if(res == -1)
{
perror("bind udp socket failed!\n");
return -1;
}
while(1)
{
puts("111");
bzero(buf,50);
recvfrom(udpsocket,buf,50,0,(struct sockaddr *)&raddr,&ret);
printf("message recv from %s\n",buf);
}
close(udpsocket);
return 0;
}
//this is for send message
int main(int argc,char **argv)
{
int udpsocket;
int res;
char buf[50];
struct sockaddr_in saddr;
bzero(&saddr,sizeof(saddr));
// 初始化地址结构体变量
saddr.sin_family = AF_INET;
saddr.sin_port = htons(5001);
saddr.sin_addr.s_addr = inet_addr(argv[1]);
// 创建udp套接字
udpsocket = socket(AF_INET,SOCK_DGRAM,0);
if(udpsocket == -1)
{
perror("create udp socket failed!\n");
return -1;
}
// 将套接字的属性设置为可以广播
int on = 1;
setsockopt(udpsocket, SOL_SOCKET, SO_BROADCAST, &on, sizeof on);
setsockopt(udpsocket,SOL_SOCKET,SO_REUSEADDR,&on,sizeof on);
int ret = sizeof(struct sockaddr);
while(1)
{
bzero(buf,50);
printf("please input a message !\n");
scanf("%s",buf);
sendto(udpsocket,buf,50,0,(struct sockaddr *)&saddr,ret);
}
close(udpsocket);
return 0;
}