enum { max_msg = 1024 };
char read_buffer_[max_msg];

void do_read()
{
    async_read(m_sock, buffer(read_buffer_),
               boost::bind(read_complete,_1,_2),
               boost::bind(on_read,_1,_2));
}

size_t read_complete(const boost::system::error_code & err, size_t bytes)
{
    if ( err) return 0;
    bool found = std::find(read_buffer_, read_buffer_ + bytes, 'n') < read_buffer_ + bytes;
    // we read one-by-one until we get to enter, no buffering
    return found ? 0 : 1;
}