> RealLength is determined by using a server side "bytes per character",

Nope. As Vlad said, on server RealLength is always == N for CHAR.

On client RealLengthInChars cannot be determined from RealLengthInBytes.
Consider this example: CHAR(4), containing some characters in UTF8
encoding. First character has size 1 byte, second - 2 bytes and the last
one is 4 bytes. RealLengthInBytes = 7, bytes_per_character = 4,
buffer_size = 16. Show me the way to calculate RealLengthInChars (which
is 3) from numbers above.

SY, SD.