c++ - boost::asio 加入了错误的接口(interface)

Question

我有一个双组播设置，其中每个组播组都需要连接到我服务器上的特定接口(interface)。

Coliru

#include <boost/asio.hpp>
#include <iostream>

namespace ip = boost::asio::ip;
using ip::udp;

boost::asio::io_service io;

struct Connection {
    int32_t timeout = 5000;
    udp::socket sock {io};
    ip::address addr;

    bool Connect(std::string const& localAddr, std::string const& addrStr, int port, boost::system::error_code& ec) {
        // Multicast socket
        udp::endpoint local(ip::address::from_string(localAddr), port); // leaving host/port unbound doesn't seem to help

        std::cout << "Using local " << local << "\n";
        addr = ip::address::from_string(addrStr);
        udp::endpoint multicastEndpoint(addr, port);

        sock.open(multicastEndpoint.protocol());
        // The commented flags don't seem to have any effect on the findings
        //sock.set_option(ip::multicast::enable_loopback());
        sock.bind(local, ec);
        sock.set_option(ip::multicast::join_group(addr.to_v4()));
        sock.set_option(udp::socket::reuse_address(true));
        //setsockopt(sock.native(), SOL_SOCKET, SO_RCVTIMEO, (const char *)&timeout, sizeof(timeout));

        return ec? false : true;
    }
};

struct ConnectionPair {
    Connection a, b;

    bool Connect(std::string const& addrStrA, int portA, std::string const& addrStrB, int portB, boost::system::error_code& ec) {
        // Example adresses; Replace with your local adapter addresses
        return a.Connect("172.17.0.1",     addrStrA, portA, ec) 
            && b.Connect("192.168.195.62", addrStrB, portB, ec);
    }
};

int main() {
    try {
        ConnectionPair pair;
        boost::system::error_code ec;

        // all hosts multicast groups
        if (pair.Connect("224.0.0.251", 5656, "224.0.0.1", 5657, ec)) {
            std::cout << "Both connected... ";
            boost::asio::deadline_timer dlt(io, boost::posix_time::seconds(5));
            dlt.wait();
        } else {
            std::cout << "Connection error: " << ec.message() << "\n";
        }
    } catch(std::exception const& e) {
        std::cout << "Exception: '" << e.what() << "'\n";
    }
    std::cout << "Bye\n";
}

问题是，当使用它进行连接时，套接字 A 没有获取任何数据。使用netsh interface ip show join，显示两个多播组都已加入到localAddrB对应的接口(interface)中，而不是各自在各自的位置。

当使用mdump 加入多播组时，每个组都连接到正确的位置并接收数据。

我不知道我的代码哪里出了问题。

Answer 1

您可以指定广播/加入多播组的接口(interface)。

http://www.boost.org/doc/libs/1_47_0/boost/asio/ip/detail/socket_option.hpp

这两行:

this->socket.set_option(ip::multicast::outbound_interface(ip::address_v4::from_string(this->address)));

this->socket.set_option(ip::multicast::join_group(joinAddress, listenInterface));

在上下文中:

• 服务器代码:

  this->socket.open(ip::udp::v4());
  this->socket.set_option(ip::udp::socket::reuse_address(true));
  this->socket.set_option(ip::multicast::enable_loopback(true));
  this->socket.set_option(ip::multicast::hops(HOPS));
  
  this->socket.set_option(ip::multicast::outbound_interface(ip::address_v4::from_string(this->address)));
  this->socket.bind(ip::udp::endpoint(ip::address_v4::from_string(this->address), 0)); // any port
  
  this->ioService.run(); // blocking
  

• 客户代码:

  udp::endpoint bindEndpoint(ip::address_v4::any(), UDPMulticastServer::PORT);
  this->socket.open(ip::udp::v4());
  this->socket.set_option(ip::udp::socket::reuse_address(true));
  this->socket.bind(bindEndpoint);
  
  // Join the multicast group on a specific interface
  ip::address_v4 joinAddress = ip::address_v4::from_string(UDPMulticastServer::MULTICAST_ADDRESS);
  ip::address_v4 listenInterface = ip::address_v4::from_string(this->address);
  this->socket.set_option(ip::multicast::join_group(joinAddress, listenInterface));
  
  this->listenForBroadcast();
  this->ioService.run(); // blocking