A Kiwi chap named Jeff Harris has created a Slack client for the Commodore 64.
Harris has no explanation for why he thinks the world needs a Slack client for the Commodore 64, but built one anyway. As he
writes, he just felt like it was a good idea to write one. So he did.
To do so, he wrote a NodeJS app for the Raspberry Pi. That app talks to Slack's real-time messaging API, the basis for all Slack clients. The Commodore 64 makes a remote procedure call to the Pi, over what Harris calls an “artisanal, locally sourced, homemade cable” with a Commodore C64 Userport plug on one and and USB on the other. On the Commodore end, the code's all 6502 assembly language.
Once everything's running and plugged in – hey, presto! - grandad's on Slack, albeit in a limited way because the 64-to-Pi connection tops out at just 1200 baud