Slack, minus the ability to gracefully run in any sort of long term roaming context without babysitting. There's no decent reconnecting logic on either client or server, you just have to notice it's gone quiet, and then figure out the undocumented way to restore it without nuking your settings. Only figured out by accident "/connect" without parameters is valid.

I tried to fix it, but the client is a pile of terrible code and needs a complete rewrite.