How would I do this?

Well, I see two ways.

 

First, ensuring you are connected to a server, you can use reflection to access serverName in Minecraft. But that's probably not the best idea.

 

The better way is to create a ConnectionHandler. Simply make a class:

public class ConnectionHandler implements IConnectionHandler

 

and register it in your @Init using:

NetworkRegistry.instance().registerConnectionHandler(new ConnectionHandler());

 

You can then use to these to methods in your connection handler to keep track of the current server:

@Override
public void connectionOpened(final NetHandler netClientHandler, final String server,
		final int port, final INetworkManager manager) {

}

@Override
public void connectionClosed(final INetworkManager manager) {

}

So, could you give me an example of how to use this to add a stat (achievement) to the player?

(for an example) how would i use this to activate

player.addStat(ExtraAchievments.prot3ch, 1);

when the player connects to a server with the IP "173.68.68.76"?

 

Im asking because my mod (ExtraAchievements) is being added to a modpack I used to work on and i want to add an achievement for playing on the modpack's server.

For that, I would use the playerLoggedIn method since it is fired server side when the connection is actually established. I haven't actually tried it, but this should work in your connection handler:

 

@Override
public void playerLoggedIn(final Player player, final NetHandler netHandler,
		final INetworkManager manager) {
	if(player instanceof EntityPlayerMP)
		((EntityPlayerMP)player).addStat(ExtraAchievments.prot3ch, 1);
}

 

EDIT: I forgot to mention, you're going to want to make sure that code is actually running on the intended server. Using this, someone could just create a local server and join to get the achievement. Perhaps an encrypted key in a configuration file?

Thanks for the help!

I've been thinking a bit more and it might just be best to use connectionOpened and check the server String . As I edited, they could just create a local server using the above method.