Wow, now this is “bonkers.” A Slack client for Windows 3.1? Almost, but HTTPS is done by an external proxy, of course. Almost all of the code had to be custom written to confirm with the C89 toolchain constraints. This article is also a great reference for how to setup a Windows 3.1 development environment on modern hardware. Technically, the development target is for Windows for Workgroups 3.11.
And, I have a copy of the book mentioned in the article! Great, now I know how to put it to good use… I better get to digitizing it as a top-priority project if it is no already in the Internet Archive.
20191220/http://yeokhengmeng.com/2019/12/building-a-new-win-3-1-app-in-2019-part-1-slack-client/
That floppy disk? Lucky for us, the author of the blog article uploaded all the source code on the floppy disk to this GitHub reposiory online.
20191220/https://github.com/yeokm1/programming-win31