While linux x86_64 only, this is precisely why I built sshtalk -- https://2ton.com.au/sshtalk, or just ssh 2ton.com.au to see for yourself, I leave it open as a public/free service
My dad and I have been using it for our instant messaging. We were curious how possible it would be to have timestamps on messages. I suppose we could reprogram the ASM, but x86 ASM is a little inaccessible :)