IRC... But yes, Slack is basically IRC with a built in bouncer. And i case people wonder, a bouncer or BNC, was a personal proxy that would be running on some

IRC... But yes, Slack is basically IRC with a built in bouncer. And i case people wonder, a bouncer or BNC, was a personal proxy that would be running on some server somewhere, and that maintained a presence on the IRC networks for you when you logged off. And when you logged back on, you got a log of all the traffic on the relevant channels and direct messages while you were gone.