It seems like executing a request to a URI such as HTTP://EXAMPLE.COM/ will try to send the request to port 443 rather than 80, resulting in various kinds of errors. This was originally reported as a Play Framework issue at playframework/playframework#5820.

I created a project demonstrating the issue: https://github.com/gmethvin/asynchttpclient-uppercase

This seems to be fixed in 1.9 but I'm not sure fixing it was intentional. I didn't see any pull requests or issues mentioning the problem.