Question

我需要通过一个以太网连接从两个源接收多播数据，即224.0.31.132端口14384和224.0.31.130端口14382。首先，我尝试与端口14384绑定，然后加入两个IP地址，但我仅从224.0.31.132获得数据。如果我与14382绑定并同时加入两者，则只能从224.0.31.130获得数据。因此，然后我尝试创建两个套接字，将第一个套接字绑定到14384并加入224.0.31.132，然后将第二个套接字绑定到14382并加入224.0.31.130。当我这样做时，我从224.0.31.130获得了数据，但没有从224.0.31.132获得数据，并且ip maddr show显示到224.0.31.132的联接显然已被第二个套接字的设置删除。
如何在单个eth端口上从这两个来源接收数据？

以下是第一种方法的代码：

// Activity class
Intent intent = new Intent(this, DetailsActivity.class);
// multiple instances can be launched without this line
intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT); 
startActivityForResult(intent, REQUEST_CODE_DETAILS);

// AndroidManifest.xml
<activity
    android:name=".DetailsActivity"
    android:launchMode="singleTop"/>

以下是结果输出：

/* Create a datagram socket on which to receive. */
int sd = socket(AF_INET, SOCK_DGRAM, 0);
if(sd < 0)
{
  perror("Opening datagram socket error");
  exit(1);
}
else
  cout<<"Opening datagram socket....OK."<<endl;

/* Enable SO_REUSEADDR to allow other */
/* applications to receive copies of the multicast datagrams. */
{
  int reuse = 1;
  if(setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0)
  {
    perror("Setting SO_REUSEADDR error");
    close(sd);
    exit(1);
  }
else
  cout<<"Setting SO_REUSEADDR...OK."<<endl;
}

/* Enable SO_REUSEPORT to allow multiple uses of receive port */
{
  int reuse = 1;
  if(setsockopt(sd, SOL_SOCKET, SO_REUSEPORT, (char *)&reuse, sizeof(reuse)) < 0)
  {
    perror("Setting SO_REUSEPORT error");
    close(sd);
    exit(1);
  }
else
  cout<<"Setting SO_REUSEPORT...OK."<<endl;
}

/* Bind to the proper port number with the IP address */
/* specified as INADDR_ANY. */
struct sockaddr_in localSock;
memset((char *) &localSock, 0, sizeof(localSock));
localSock.sin_family = AF_INET;
localSock.sin_port = htons(14384);
localSock.sin_addr.s_addr = INADDR_ANY;
if(bind(sd, (struct sockaddr*)&localSock, sizeof(localSock)))
{
  perror("Binding datagram socket error");
  close(sd);
  exit(1);
}
else
  cout<<"Binding datagram socket...OK."<<endl;

/* Join the multicast groups on the local nic interface. */
struct ip_mreq group;
group.imr_interface.s_addr = inet_addr("0.0.0.0");
int ipcount = stoi(getSetup("mcstcount"));
while(ipcount>0)
{
  string which = "listenip" + to_string(ipcount);
  cout<<"listen to "<<getSetup(which.c_str())<<endl;
  group.imr_multiaddr.s_addr = inet_addr(getSetup(which.c_str()).c_str());
  ipcount--;
  if(setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&group, sizeof(group)) < 0)
  {
    perror("Adding multicast group error");
    close(sd);
    exit(1);
  }
  else
    cout<<"Adding multicast group...OK."<<endl;
}

// process Mdp feed
while( !stop_cond  ) 
{
  /* Read from the socket. */
  const int DBUFSZ = 5000;
  uint8_t databuf[DBUFSZ];
  int datalen;
  datalen=read(sd, databuf, DBUFSZ);
  if(datalen < 0)
  {
    perror("Reading datagram message error");
    close(sd);
    exit(1);
  }

  //process data
}

但是数据仅来自224.0.31.132。

Answer 1

结论是不能使用单个套接字，因为有多个端口可以接收。返回到第二种方法，使用多个插座。一切正常，不知道第一次出什么问题。

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