关于双网卡同网段的广播问题

假设有电脑A和电脑B，A双网卡并且双网卡的IP是同一网段，并且A的网段和B的网段在同一网段，现在B进行广播，我们会看到A收到了两次信息，程序如下：

//server.cpp
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>

char * host_name = "192.168.0.255";
int port = 10051;

int main(void)
{
struct sockaddr_in serv_addr,addr;
char buf[256];

int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1)
{
perror("Error: socket";
return -1;
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr(host_name);//htonl(INADDR_ANY);//

int bd = bind(sockfd, (struct sockaddr*)&addr, sizeof(struct sockaddr_in));
while(1)
{
int len = sizeof(serv_addr);
memset(&serv_addr, 0, len);
int ret = recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&serv_addr,(socklen_t*)&len);
printf("recv=%d buf=%s
",ret, buf);
printf("RecvieIPs Recive Portd
", inet_ntoa(serv_addr.sin_addr),
ntohs(serv_addr.sin_port));
ret = sendto(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&serv_addr,sizeof(struct sockaddr_in));
}

}


//client.cpp

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>

char * host_name = "192.168.0.255";

int port = 10051;
int main(void)
{
int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1)
{
perror("Error: socket";
return -1;
}

struct sockaddr_in serv_addr;
memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(port);
serv_addr.sin_addr.s_addr = inet_addr(host_name);
int so_broadcast;
setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &so_broadcast,
sizeof(so_broadcast));

char buf[256]="client .............";
sockaddr from ;
int len;
sendto(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&serv_addr,sizeof(struct sockaddr_in));
while(1)
{
recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&serv_addr,(socklen_t*)&len);
printf("server buf= %s
",buf);
}
}

我们会看到上面接收端绑定的IP是针对子网的广播，而发送端发送的IP也是针对于子网的广播，我们可以ROUTE PRINT一下，看看自己电脑的路由表（如果不懂怎么看，请百度）。如果是双网卡同网段，那么到同一个网段的IP将有两个，所以就接收了两次，我曾试过发送端绑定255.255.255.255，结果只发送一次，但是让人不解的是路由表中对于目的地址为255.255.255.255的依旧是两个，所以我只能推断上面那个哥们的程序不是在双网卡机子上进行的，仅仅是一网卡多IP，因为电脑只会在某一时刻让一个网卡工作，而在广播也只收一次。