Indeed I have, I couldn't send emoji with my scripts. I suspect that TCPSend is screwing with the encoding. You will have to manually find a way to convert your messages string to properly formatted UTF-8 binary and then send that directly with TCPSend.
By the way, don't bother with BOM, it is fairly useless and even undesired, so it won't help you with anything but it can for sure screw up your text potentially if programs are not properly made to handle it.
AutoIt's own IniRead function will fail if the file has a BOM.