c++ - boost::asio::ip::tcp::socket 不读取任何内容

Question

这实际上是我在套接字编程方面的第一个程序，而不是复制粘贴教程代码并从中获得乐趣。无论如何它不起作用。我想我已经仔细阅读了文档，但也许还不够。我怀疑我在 read_message() 中使用了 socket::read_some()，因为我有问题的程序在读取部分停止了。我认为我使用它的方式应该没问题，因为 socket::read_some() 的文档指出“函数调用将阻塞，直到一个或多个字节的数据被成功读取，或者直到一个发生错误。”下面是我的代码。任何帮助表示赞赏。

void read_message(std::string& message, boost::asio::ip::tcp::socket& socket)
{
    std::stringstream message_stream;
    while (true)
    {
        std::array<char, 128> buffer;
        boost::system::error_code error;
        size_t len = socket.read_some(boost::asio::buffer(buffer), error);
        if (error == boost::asio::error::eof)
        {
            break;
        }
        message_stream.write(buffer.data(), len);
    }
    message = message_stream.str();
}

服务器.cpp

int main()
{
    while (true)
    {
        boost::asio::io_service io_service;
        boost::asio::ip::tcp::acceptor acceptor(io_service, boost::asio::ip::tcp::endpoint(
            boost::asio::ip::tcp::v4(), 9999));
        boost::asio::ip::tcp::socket socket(io_service);
        acceptor.accept(socket);
        std::cout << "connected with client, waiting for a message\n";
        std::string message;
        read_message(message, socket);
        boost::asio::ip::tcp::endpoint endpoint = socket.remote_endpoint();
        std::cout << "message received from " << endpoint.address().to_string() <<
            ':' << endpoint.port() << '\n' << message << '\n';
        boost::asio::write(socket, boost::asio::buffer(message));
        if (message.compare("quit") == 0)
        {
            break;
        }
    }
    return EXIT_SUCCESS;
}

客户端.cpp

int main()
{
    while (true)
    {
        std::cout << "your message to be sent: ";
        std::string message;
        std::getline(std::cin, message);
        boost::asio::io_service io_service;
        boost::asio::ip::tcp::resolver resolver(io_service);
        boost::asio::ip::tcp::resolver::query query("localhost", "9999");
        boost::asio::ip::tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
        boost::asio::ip::tcp::socket socket(io_service);
        boost::asio::connect(socket, endpoint_iterator);
        std::cout << "connected to server\n";
        boost::asio::write(socket, boost::asio::buffer(message));
        read_message(message, socket);
        std::cout << "message received from server: " << message << '\n';
        if (message.compare("quit") == 0)
        {
            break;
        }
    }
    return EXIT_SUCCESS;
}

Answer 1

问题出在 read_message 函数中:您一直读取到 eof，但只有当套接字关闭时您才会收到 eof。

也许您打算在遇到某些分隔符时从 read_message 返回，例如。 '\n'?然后您可以手动检查缓冲区，或使用 read_until功能。

使用 read_until 函数，read_message 将如下所示:

void read_message(std::string& message, boost::asio::ip::tcp::socket& socket)
{
  std::stringstream message_stream;
  boost::asio::streambuf buffer;
  boost::system::error_code error;
  size_t len = read_until(socket, buffer, '\n', error);
  if (len)
  {
    message_stream.write(boost::asio::buffer_cast<const char *>(buffer.data()), len);
    message = message_stream.str();
  }
}

请记住在您从客户端发送的消息中附加“\n”:

//...
std::cout << "connected to server\n";
boost::asio::write(socket, boost::asio::buffer(message + '\n'));
read_message(message, socket);
//...