boost::asio::read function hanging

Question

If someone could please help me out, I cannot understand how the boost::asio::read function works in boost asio. In boost\'s example they have it declare the buffer size before

Answer 1

I've encountered the same problem. It seems that boost::asio::read is supposed to be hang there until the connected client is closed. Instead, you can use socket.read_some like this:

using boost::asio::ip::tcp;
try {
    boost::asio::io_service io_service;

    tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 9999));

    for (;;) {
        tcp::socket socket(io_service);
        acceptor.accept(socket);

        std::string message = "server received!\n";

        boost::system::error_code error_code;
        boost::asio::streambuf stream_buf;

        std::vector buf(1024);
        size_t len = socket.read_some(boost::asio::buffer(buf), error_code);
        std::string received_filename(buf.begin(), buf.end());
        received_filename.resize(len);
        if (error_code) {
            std::cout << "error status: " << error_code.message() << std::endl;
        }

        boost::asio::write(socket, boost::asio::buffer(message), error_code);
        if (error_code) {
            std::cout << "error status: " << error_code.message() << std::endl;
        }
        query_database(tree, received_filename, output_folder, db_image_filenames);
    }
}
catch (std::exception& e) {
    std::cerr << e.what() << std::endl;
}

This will get the message from the client instantly with a relative short message. Hope this help.