boost::asio - async_read_some and boost::asio::socket_base::bytes_readable

Question

I have a problem with the function async_read_some(). I am running cyclicly the function receiveAsyncWithTimeout() by a timer.

Expected working The function receiveAsyncWithTimeout() should read all messages from my server.

Problems

1. bytesTransferred and bytesReadable are different.
2. Messages are received weirdly. First one frame, after about 10 seconds the rest.

Boost version: 1.77

output:

readHandle bytesReadable: 0 bytesTransferred: 1112

pseudocode:

class TlsSocket 
{
public:
    TlsSocket(boost::asio::io_context &io_context,
              const std::string &endpoint);
private:
    boost::asio::io_context &_iocontext;
    boost::asio::ssl::context _ctx;
    boost::asio::ssl::stream<boost::asio::ip::tcp::socket> _socket;
    std::vector<uint8_t> _recvBuffer;
    std::vector<uint8_t> _sendBuffer;
    size_t _bytesReadable{0};
}

void TlsSocket::readHandle(const boost::system::error_code &ec, std::size_t bytesTransferred)
{
    if(_bytesReadable == 0 && bytesTransferred > 0)
    {
        std::cout << "readHandle ERROR bytesReadable: " << _bytesReadable
                  << " bytesTransferred: " << bytesTransferred << std::endl;
        return;
    }

/// .. any code
}

void TlsSocket::receiveAsyncWithTimeout()
{
    boost::asio::socket_base::bytes_readable command(true);
    _socket.lowest_layer().io_control(command);
    _bytesReadable = command.get();
    
     _socket.async_read_some(boost::asio::buffer(_recvBuffer),
                            boost::bind(&TlsSocket::readHandle,
                                        this,
                                        boost::asio::placeholders::error,
                                        boost::asio::placeholders::bytes_transferred));
}