Serial Port configuration with asio C++ library
Can you include all the other calls you make related to setting up the serial port along with asio::serial_port_base::baud_rate(baudios)? Ideally, split that out into a separate function (that takes parameters such as baud rate) that you know is the only thing doing this setup.

As I mentioned in the comment, getting back the right number of chararacters but incorrect characters looks as if the baud rate is correct but something else is wrong. The first thing that comes to mind is the bits/parity/stop bits settings. Typically you want to be using 8 bits, no parity, often referred to as "8N1".