请教linux组播问题。
我的板子用嵌入式linux系统发送组播包给我PC虚拟机的linux，虚拟机的linux可以接收到，但是同样的程序，用虚拟机的linux发送，嵌入式linux却接收不到，具体表现为阻塞在recvfrom函数。
大致已经可以排除的问题：
1、网络、交换机等问题，2台设备之间直接用网线相连，不经过任何中间设备。
2、嵌入式linux内核问题，内核编译时我已经选上支持multicast，而且嵌入式linux能发出组播包说明内核起码在一定程度上肯定支持组播了，但不知道是否还有其他选项需要选？
以下是程序：
接收端程序
-----------------
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h>
#include <signal.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <memory.h>
#define PORT 9000
#define MultiAddr "224.0.1.1"
int main(void)
{
struct ip_mreq command;
int loop = 1;
int ttl=128;
int iter = 0;
int sin_len;
char message[256];
int socket_descriptor;
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(PORT);
if((socket_descriptor = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
perror("socket");
exit(EXIT_FAILURE);
}
loop = 1;
if(setsockopt(socket_descriptor,SOL_SOCKET, SO_REUSEADDR,&loop, sizeof(loop)) < 0)
{
perror("setsockopt:SO_REUSEADDR");
exit(EXIT_FAILURE);
}
if(bind(socket_descriptor,(struct sockaddr *)&sin, sizeof(sin)) < 0)
{
perror("bind");
exit(EXIT_FAILURE);
}
ttl=64;
if(setsockopt(socket_descriptor,IPPROTO_IP, IP_MULTICAST_TTL,&ttl, sizeof(ttl)) < 0)
{
perror("setsockopt:IP_MULTICAST_TTL");
exit(EXIT_FAILURE);
}
loop = 1;
if(setsockopt(socket_descriptor,IPPROTO_IP, IP_MULTICAST_LOOP,&loop, sizeof(loop)) < 0)
{
perror("setsockopt:IP_MULTICAST_LOOP");
exit(EXIT_FAILURE);
}
command.imr_multiaddr.s_addr = inet_addr(MultiAddr);
command.imr_interface.s_addr=inet_addr("192.168.0.97");
if(command.imr_multiaddr.s_addr == -1)
{
perror("224.0.0.1 not a legal multicast address");
exit(EXIT_FAILURE);
}
if (setsockopt(socket_descriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP,&command, sizeof(command)) < 0)
{
perror("setsockopt:IP_ADD_MEMBERSHIP");
}
while(iter++ < 8)
{
sin_len = sizeof(sin);
if(recvfrom(socket_descriptor,message,32,0,(struct sockaddr *)&sin, &sin_len) == -1)
{
perror("recvfrom");
}
printf("Response #%-2d from server: %s\n", iter, message);
sleep(2);
}
if(setsockopt(socket_descriptor, IPPROTO_IP, IP_DROP_MEMBERSHIP,&command, sizeof(command)) < 0)
{
perror("setsockopt:IP_DROP_MEMBERSHIP");
}
close(socket_descriptor);
exit(EXIT_SUCCESS);
}
------------
发送端程序
-------------------
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <unistd.h>
#define PORT 9000
#define MultiAddr "224.0.1.1"
int main(int argc,char* argv[])
{
int udp_sockfd;
struct sockaddr_in cliaddr,udpsrvaddr;
char Head[12];
long sendbytes;
int val=1;
int ttl=128;
sendbytes = 0;
memset(&udpsrvaddr,0,sizeof(udpsrvaddr)); //clear the struct of address
udpsrvaddr.sin_family=AF_INET;
udpsrvaddr.sin_port=htons(PORT);
udpsrvaddr.sin_addr.s_addr=inet_addr(MultiAddr);
cliaddr.sin_family=AF_INET;
cliaddr.sin_port=htons(PORT);
cliaddr.sin_addr.s_addr=inet_addr("192.168.0.117");
if ((udp_sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
printf("socket create error\n");
return 1;
}
if(setsockopt(udp_sockfd,SOL_SOCKET,SO_REUSEADDR,(char*)&val,sizeof(int))<0)
{
printf("set SO_REUSEADD error\n");
return 1;
}
if(bind(udp_sockfd,(struct sockaddr*)&cliaddr,sizeof(cliaddr))<0)
{
printf("bind erro\n");
return 1;
}
if(setsockopt(udp_sockfd,IPPROTO_IP,IP_MULTICAST_TTL,(char*)&ttl,sizeof(int))<0)
{
printf("set TTL error\n");
return 1;
}
printf("before send data \n");
printf("send data\n");
if((sendbytes = sendto(udp_sockfd,"Head",4,0,(struct sockaddr *)&udpsrvaddr,sizeof(udpsrvaddr)))<0)
{
perror("sendto");
exit(1);
}
printf("send data end\n");
printf("the bytes have sended is %d\n",sendbytes);
sendto(udp_sockfd,"End",3,0,(struct sockaddr *)&udpsrvaddr,sizeof(udpsrvaddr));
printf("send tail end\n");
return 0;
}
[解决办法]
PC虚拟机的路由是怎么设置的？
route, 嵌入式板的ip? 虚拟机的ip?
[解决办法]
组播数据包要成功发出来得有对应的路由设置,
你分别在虚拟机上跟嵌入式板子上运行route看一下当前的路由配置.
另外你可以用一个抓包工具看一下组播包有没有实际发出来.
