sockfd_to_family函数

#include    <sys/socket.h>
#include    <netinet/in.h>

#define     SA    struct sockaddr

int sockfd_to_family(int sockfd)
{
    struct sockaddr_storage ss;
    socklen_t    len;

    len = sizeof(ss);
    if (getsockname(sockfd, (SA *) &ss, &len) < 0)
        return(-1);
    return(ss.ss_family);
}