c++ - Boost ASIO，不调用 async_read_some 回调

Question

我的代码适用于 read_some，但不适用于 async_read_some。我正在读取的数据长度为 5 个字符，而 MAX_RESPONSE_SIZE 256。打开端口后，我从 main 中调用了一次 async_read_some，但在我刷了几次代理卡后，回调从未被调用过。我尝试在 async_read_some 之后添加 io_service.run() 但它没有帮助。我错过了什么吗？谢谢。

标题

boost::system::error_code error;
boost::asio::io_service io_service;
typedef boost::shared_ptr<boost::asio::serial_port> serial_port_ptr;
serial_port_ptr serial_port;
char read_buffer[MAX_RESPONSE_SIZE];

打开

serial_port.reset();
serial_port = serial_port_ptr(new boost::asio::serial_port(io_service));
serial_port->open(device_path, error);

serial_port->set_option(boost::asio::serial_port_base::baud_rate(baud_rate));
serial_port->set_option(boost::asio::serial_port_base::character_size(8));
serial_port->set_option(boost::asio::serial_port_base::stop_bits(boost::asio::serial_port_base::stop_bits::one));
serial_port->set_option(boost::asio::serial_port_base::parity(boost::asio::serial_port_base::parity::none));
serial_port->set_option(boost::asio::serial_port_base::flow_control(boost::asio::serial_port_base::flow_control::none));

boost::thread t(boost::bind(&boost::asio::io_service::run, &io_service));

阅读

serial_port->async_read_some(
            boost::asio::buffer(read_buffer, MAX_RESPONSE_SIZE),
            boost::bind(
                &serial_comm::data_received,
                this, boost::asio::placeholders::error,
                boost::asio::placeholders::bytes_transferred
            )
        );

回调

void serial_comm::data_received(const boost::system::error_code& error, size_t bytes_transferred)
{
    // do stuff
}

Answer 1

您必须确保始终有工作要做，以便 io_service::run() 不会返回并完成它正在运行的线程。

如评论中所述，您可以创建一个 io_service::work。但是，我认为这是人为的，是设计问题的征兆。

可能更好的答案是，在 data_received 处理程序中，如果没有发生 fatal error ，您应该准备下一次读取

void serial_comm::data_received(
  const boost::system::error_code& error,
  size_t bytes_transferred)
{
    // do stuff

   if( any_kind_of_fatal_error )
   {
       // return without setting up the next read
       // this will end reading
      return;
   }

   // the last read was successful
   // so setup for the next
   serial_port->async_read_some(
        boost::asio::buffer(read_buffer, MAX_RESPONSE_SIZE),
        boost::bind(
            &serial_comm::data_received,
            this, boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred
        )
    );

}