我看到的一切告诉我,UDP组播是在IPv6中这样做的正确方法.我已经找到一些示例代码,但是在我尝试过的任何版本的iOS或Mac OS X上都无效.

这个代码是从我们程序中的C/C++ lib调用的 – 很难回调到Swift,Obj-C,Java等.这段代码将由我们的应用程序的Mac OS X和Android版本共享.有人会认为可以在任何POSIX环境中的C中进行IPv6组播！

在下面的示例中,执行成功到最终的sendto()调用,实际发送UDP消息.失败后sendto()失败,errno设置为EBROKENPIPE(22).

我最好的猜测是我缺少一些需要的setsockopt()调用,或者使用错误的多播地址.现在,我被困了

这是我正在做的函数调用(在UDP端口4031上多播“有人在吗？”)：

char *msg = "Is anybody out there?";
err = multicast_udp_msg ( "FF01::1111",4031,msg,strlen(msg) );

这是正在调用的代码：

// Multicasts a message on a specific UDP port.
// myhost - IPv6 address on which to multicast the message (i.e.,ourself)
// port - UDP port on which to broadcast the mssage
// msg - message contents to broadcast
// msgsize - length of message in bytes
// Return value is zero if successful,or nonzero on error.

int multicast_udp_msg ( char *myhost,short port,char *msg,size_t msgsize )
{
    int        sockfd,n;
    char    service[16] = { 0 };
    int        err = 0;
    struct addrinfo hints = { 0 },*res,*ressave;
    struct sockaddr_storage addr = { 0 };

    hints.ai_family = AF_INET6;
    hints.ai_socktype = SOCK_DGRAM;

    sprintf ( service,"%hd",port );
    n = getaddrinfo ( myhost,service,&hints,&res );
    if ( n < 0 )
    {
        fprintf(stderr,"getaddrinfo error:: [%s]\n",gai_strerror(n));
        return -1;
    }

    ressave = res;

    sockfd = socket ( res->ai_family,res->ai_socktype,res->ai_protocol );
    if ( sockfd >= 0 )
    {
        memcpy ( &addr,res->ai_addr,sizeof ( addr ) );
        if ( joinGroup ( sockfd,8,&addr ) == 0 )
            if ( bind ( sockfd,res->ai_addrlen ) == 0 )
                if ( sendto ( sockfd,msgsize,(struct sockaddr *) &addr,sizeof ( addr ) ) < 0 )
                    err = errno;

        close ( sockfd );

        res = res->ai_next;
    }

    freeaddrinfo ( ressave );
    return err;
}

int
joinGroup(int sockfd,int loopBack,int mcastTTL,struct sockaddr_storage *addr)
{
    int r1,r2,r3,retval;

    retval=-1;

    switch (addr->ss_family) {
        case AF_INET: {
            struct ip_mreq      mreq;

            mreq.imr_multiaddr.s_addr=
            ((struct sockaddr_in *)addr)->sin_addr.s_addr;
            mreq.imr_interface.s_addr= INADDR_ANY;

            r1= setsockopt(sockfd,IPPROTO_IP,IP_MULTICAST_LOOP,&loopBack,sizeof(loopBack));
            if (r1<0)
                perror("joinGroup:: IP_MULTICAST_LOOP:: ");

            r2= setsockopt(sockfd,IP_MULTICAST_TTL,&mcastTTL,sizeof(mcastTTL));
            if (r2<0)
                perror("joinGroup:: IP_MULTICAST_TTL:: ");

            r3= setsockopt(sockfd,IP_ADD_MEMBERSHIP,(const void *)&mreq,sizeof(mreq));
            if (r3<0)
                perror("joinGroup:: IP_ADD_MEMBERSHIP:: ");

        } break;

        case AF_INET6: {
            struct ipv6_mreq    mreq6;

            memcpy(&mreq6.ipv6mr_multiaddr,&(((struct sockaddr_in6 *)addr)->sin6_addr),sizeof(struct in6_addr));

            mreq6.ipv6mr_interface= 0; // cualquier interfaz

            r1= setsockopt(sockfd,IPPROTO_IPV6,IPV6_MULTICAST_LOOP,sizeof(loopBack));
            if (r1<0)
                perror("joinGroup:: IPV6_MULTICAST_LOOP:: ");

            r2= setsockopt(sockfd,IPV6_MULTICAST_HOPS,sizeof(mcastTTL));
            if (r2<0)
                perror("joinGroup:: IPV6_MULTICAST_HOPS::  ");

            r3= setsockopt(sockfd,IPV6_JOIN_GROUP,&mreq6,sizeof(mreq6));
            if (r3<0)
                perror("joinGroup:: IPV6_ADD_MEMBERSHIP:: ");

        } break;

        default:
            r1=r2=r3=-1;
    }

    if ((r1>=0) && (r2>=0) && (r3>=0))
        retval=0;

    return retval;
}

想念欢迎！

-Tim