Yes you are correct, earlier I had made the mistake to use struct.pack("i", 4) in python which returned byte representation in little-endian (my native), but Elixir defaults to big-endian, which I never knew 
Add that to the fact I do not really know Ruby and did not realize, or read closely, that [msg.bytesize].pack(“N”) encodes as an unsigned big-endian integer and I floated off into the confused.
