c++ - Linux 多播后续套接字窃取数据

Question

我正在尝试使用 Boost ASIO UDP 套接字来多播数据。我相信我有功能正常的发送者和接收者，因为单个发送者和接收者的一切都按预期工作。然而，当我们现在在同一台机器上有多个接收器时，只有最后绑定(bind)到该地址的接收器才会接收数据。我相信这可能是一个配置问题，但我会提供我能提供的一切。

网络:

[root@dev ~]# ifconfig
eth1      Link encap:Ethernet  HWaddr 00:0C:29:C1:34:B7  
          inet addr:192.168.6.131  Bcast:192.168.6.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fec1:34b7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:25060380 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24562809 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2030905679 (1.8 GiB)  TX bytes:5249474660 (4.8 GiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:2687213321 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2687213321 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1633558802477 (1.4 TiB)  TX bytes:1633558802477 (1.4 TiB)

多播发送者:

MulticastSender(const std::string& listenaddress,
                const std::string& multicastaddress,
                const unsigned short port) : Address(boost::asio::ip::address::from_string(listenaddress)),
                                             Port(port),
                                             Endpoint(Address, port),
                                             Socket(IOService, Endpoint.protocol()),
                                             Work(IOService) {
        Socket.set_option(boost::asio::ip::multicast::join_group(boost::asio::ip::address::from_string(multicastaddress).to_v4(), boost::asio::ip::address::from_string(listenaddress).to_v4()));
        auto self = this;
        WorkThread = std::thread([self]()
                                 {
                                     self->IOService.run();
                                 });

    }

组播接收器:

MulticastReceiver(const std::string &listenaddress,
                  const std::string &multicastaddress,
                  const unsigned short port) : Socket(IOService),
                                               ListenAddress(listenaddress),
                                               MulticastAddress(multicastaddress),
                                               Work(IOService) {
    boost::asio::ip::udp::endpoint listenendpoint(boost::asio::ip::udp::v4(), port);
    boost::system::error_code ec;
    Socket.open(listenendpoint.protocol(), ec);
    Socket.set_option(boost::asio::ip::udp::socket::reuse_address(true), ec);
    Socket.set_option(boost::asio::ip::multicast::enable_loopback(true), ec);
    Socket.bind(listenendpoint, ec);
    Socket.set_option(boost::asio::ip::multicast::join_group(boost::asio::ip::address::from_string(multicastaddress).to_v4(), boost::asio::ip::address::from_string(listenaddress).to_v4()), ec);
    auto self = this;
    WorkThread = std::thread([self]()
                             {
                                 self->IOService.run();
                             });
    Socket.async_receive_from(boost::asio::buffer(Buffers[BufferIndex], MaxLength), Endpoint,
                              boost::bind(&MulticastReceiver::HandleReceiveFrom, this,
                                          boost::asio::placeholders::error,
                                          boost::asio::placeholders::bytes_transferred));
}

对于 listenaddress 我已经尝试使用 192.168.6.131 指定接口(interface)，并且还尝试使用 0.0.0.0 将其留给系统。我还尝试了 join_group 的两种变体，您可以在其中指定接口(interface)，也可以不指定接口(interface)。

当我运行应用程序时，运行 netstat -gn 时，我可以在正确的地址中看到正确的成员数量。

以下是我对发送者和接收者的输入:

listenaddress = "0.0.0.0"; // or listenaddress = "192.168.6.131"; // eth1
multicastaddress = "239.140.127.0";
port = 35000;

我在 CentOS 6.6 with kernel Linux dev 2.6.32-504.el6.x86_64 上运行它并运行 Boost 1.55.0 。

Answer 1

我无法弄清楚为什么多播在该设置上不起作用，但我能够让代码在其他地方工作，所以我想我不妨发布发送者和接收者的更改。

多播发送者:

MulticastSender(const std::string& multicastaddress,
                const unsigned short port) : Port(port),
                                             Endpoint(boost::asio::ip::address::from_string(multicastaddress), port),
                                             Socket(IOService, Endpoint.protocol()),
                                             Work(IOService) {
    auto self = this;
    WorkThread = std::thread([self]()
                             {
                                 self->IOService.run();
                             });

    std::string data = "Test message";
    Socket.async_send_to(boost::asio::buffer(data), Endpoint, boost::bind(&MulticastSender::SendHandler, this, boost::asio::placeholders::error));
}

组播接收器:

MulticastReceiver(const std::string &listenaddress,
                  const std::string &multicastaddress,
                  const unsigned short port,
                  const int numbuffers) : Socket(IOService),
                                          ListenAddress(listenaddress),
                                          MulticastAddress(multicastaddress),
                                          Work(IOService) {
    boost::asio::ip::udp::endpoint listenendpoint(boost::asio::ip::address::from_string(listenaddress), port);
    boost::system::error_code ec;
    Socket.open(listenendpoint.protocol(), ec);
    Socket.set_option(boost::asio::ip::udp::socket::reuse_address(true), ec);
    Socket.set_option(boost::asio::ip::multicast::enable_loopback(true), ec);
    Socket.bind(listenendpoint, ec);
    Socket.set_option(boost::asio::ip::multicast::join_group(boost::asio::ip::address::from_string(multicastaddress)), ec);
    auto self = this;
    WorkThread = std::thread([self]()
                             {
                                 self->IOService.run();
                             });
    Socket.async_receive_from(boost::asio::buffer(Buffers[BufferIndex], MaxLength), Endpoint,
                              boost::bind(&MulticastReceiver::HandleReceiveFrom, this,
                                          boost::asio::placeholders::error,
                                          boost::asio::placeholders::bytes_transferred));
}