I'm somewhat new to modding and I'm trying to figure out how to get any player's information such as their skin, the server they're on (if connected to one), and so on.

 

Is there a way I can do this with the 1.8 Forge API? Is there an API I could use to access this information?

 

EDIT: For those wondering why I need this information, I'm trying to make a friend list mod so me and my friends can follow each other around more easily.

It's pretty simple to get a player when you and they are on a server together. I presume it is FAR more difficult to do so when you just want to get that information without being on the server with them. I am not sure how to go about this, but I would assume it would require accessing Minecraft account servers that hold all that information.

I don't think that auth server would even have a clue as to whether the person is currently online or not, much less which server they are on.

Would it be possible to send packets that tell the server IP from clients of players who have the mod and if so, how would I go about that?

Also, on the topic of getting player skins, how would I do that?

That is possbile, but far from easy.

You have to host a server, that holds "friends states".

Then you have to write your own packet system for your mod that sends and receives packets to/from your server.

Subscribe to different events in forge, and send friends state update to your server.

Finally, when you want to know state of your friend, send packet to your server and server sends you their state back.

 

Another option, without hosted server, can work only if you have fixed IPs.

In that case, you can send packets directly between your computers, and wait for answer packet. If it hasn't come, firend is offline.

But, that would require creating access ports in your modem, separate net handling and lots of other stuff.