Boost async_read_some + старые данные в буфере

void handle_handshake(const boost::system::error_code& error, int num)
    {
        if (!error)
        {
            
            socket_.async_read_some(boost::asio::buffer(data_, 1024),
                boost::bind(&Session::handle_read, this,
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred, num));
        }
        else
        {
            delete this;
        }
    }
void handle_read(const boost::system::error_code& error,
        size_t bytes_transferred, int num)
    {
        if (!error)
        {
 
std::cout << "data_: " << data_ << std::endl;
 
}
 
}

HTTP/1.0 200 OK
Content-Type: application/json
UserIP: 127.0.0.1
Host: test.com
Connection: keep-alive
Origin: https://test.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36
Content-Type: application/json
Accept: */*
Referer: https://test.com/
Accept-Language: ru,en-US;q=0.9,en;q=0.8,uk;q=0.7
Cookie: _ga=GA1.2.508780938.1527764085
Accept-Encoding: gzip, deflate
Content-Length: 39
 
{"code":"-1","msg":"","result":"err"}
 
Accept-Language: ru,en-US;q=0.9,en;q=0.8,uk;q=0.7
Cookie: _ga=GA1.2.508780938.1527764085
Accept-Encoding: gzip, deflate
Content-Length: 104

memset(data_, '\0', 1024)