Some keen eyed developers may have noticed that there's a new packet in Minecraft 1.1, with no purpose or usage anywhere in the codebase. You may be wondering why this was added, and what use it could possibly have. You may also be wondering who cares, and why you have this page open. I'm here to answer all of these questions in a nice little (disclaimer: may not be little) blog post!
Update: See the FAQ on this over here! Now with simple questions like "but what does this actually mean?"
Backstory
We did some thinking a while back, about how the state of client mods and server mods for minecraft isn't really what it could be. There's so many problems with conflicts and one mod causing a bug in another and so forth, that it's really harming the potential of Minecraft modding in general. While we by no means think that we can solve this, we did start hypothesizing ways that could at least improve how mods play together, and try to make things a nicer experience for everyone - the users, the client modders, and the server modders. Most importantly, those who fit in all of the above!
One of the biggest issues with client and server modding is that having both can be hell for your users. If you have a server mod that needs a client mod, if a user without the client mod tries to join then they'll crash with seemingly no cause. Ditto for users with client mods joining a server and crashing themselves, because the server mod isn't compatible with that client mod.
Honestly, this whole thing is a mess. I'm sure most people will agree with me here. There are attempted workarounds, sure, but ...