That sounds like it should be exactly what I'm missing. Thanks!
Just started digging in to the whole ecosystem here, so perhaps I'm just slow to grok. Created a new server side only mod and am running it from IntelliJ IDEA. Trying to connect via latest minecraft with forge installed via the forge-1.8-188.8.131.520 universal installer (forge version matches the one the server was built against). Connection drops as soon as it is made. Also tried with the mod in place on the client despite being server only (and is disabled by the loader) but got the same result. The only other threads I saw mentioning client rejections cited either a forge version mismatch or a mod version mismatch, but neither seems to be the case here. Logs are here, though they don't seem particularly interesting: https://gist.github.com/onelson/b1e11c68e245bc96adca Are server side mods not a real thing? Perhaps I need to implement a client side version of the mod that just does nothing to pass the check...