增强asio多播加入

asio::io_context io_context;
asio::ip::udp::socket socket(io_context);

asio::ip::udp::endpoint multicast_endpoint(asio::ip::address::from_string("组播地址"), 端口号);
socket.open(multicast_endpoint.protocol());
socket.set_option(asio::ip::udp::socket::reuse_address(true));
socket.bind(multicast_endpoint);
socket.set_option(asio::ip::multicast::join_group(asio::ip::address::from_string("组播地址")));

// 发送数据
std::string message = "Hello, multicast!";
socket.send_to(asio::buffer(message), multicast_endpoint);

// 接收数据
char buffer[1024];
asio::ip::udp::endpoint sender_endpoint;
size_t length = socket.receive_from(asio::buffer(buffer), sender_endpoint);