<分区>
在下面的 MulticastReceiver 实现中似乎有一个错误。
在为 <224.0.25.46,13001> 和 <224.0.25.172,13001> 创建两个实例时，我在每个流中获取每个数据包两次。任何指针？我猜是 REUSEADDR ？
class MulticastReceiverSocket {
protected:
const std::string listen_ip_;
const int listen_port_;
int socket_file_descriptor_;
public:
MulticastReceiverSocket ( const std::string & listen_ip,
const int listen_port )
: listen_ip_ ( listen_ip ), listen_port_ ( listen_port ),
socket_file_descriptor_ ( -1 )
{
/* create socket to join multicast group on */
socket_file_descriptor_ = socket ( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
if ( socket_file_descriptor_ < 0 )
{ exit(1); }
/* set reuse port to on to allow multiple binds per host */
{
int flag_on = 1;
if ( ( setsockopt ( socket_file_descriptor_, SOL_SOCKET,
SO_REUSEADDR, &flag_on,
sizeof(flag_on) ) ) < 0 )
{ exit(1); }
}
McastJoin ( );
{
/* construct a multicast address structure */
struct sockaddr_in mcast_Addr;
bzero ( &mcast_Addr, sizeof(mcast_Addr) );
mcast_Addr.sin_family = AF_INET;
mcast_Addr.sin_addr.s_addr = htonl(INADDR_ANY);
mcast_Addr.sin_port = htons ( listen_port_ );
/* bind to specified port onany interface */
if ( bind ( socket_file_descriptor_, (struct sockaddr *) &mcast_Addr, sizeof ( struct sockaddr_in ) ) < 0 )
{ exit(1); }
}
}
void McastJoin ( )
{
/* construct an IGMP join request structure */
struct ip_mreq mc_req;
inet_pton ( AF_INET, listen_ip_.c_str(), &(mc_req.imr_multiaddr.s_addr) );
mc_req.imr_interface.s_addr = htonl(INADDR_ANY);
/* send an ADD MEMBERSHIP message via setsockopt */
if ( ( setsockopt ( socket_file_descriptor_, IPPROTO_IP, IP_ADD_MEMBERSHIP,
(void*) &mc_req, sizeof(mc_req))) < 0)
{
printf ("setsockopt() failed in IP_ADD_MEMBERSHIP %s\n", listen_ip_.c_str() );
exit(1);
}
}
inline int ReadN ( const unsigned int _len_, void * _dest_ )
{
if ( socket_file_descriptor_ != -1 )
{
return recvfrom ( socket_file_descriptor_, _dest_, _len_, 0, NULL, NULL );
}
return -1;
}
请指教，当然也请指出可以做的任何改进、优化。