restriction.md

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Server-side restriction

A server can tell the CISTierTagger client to hide its badges - all of them, or one surface at a time.

The client announces itself on join by sending an empty cistiertagger:handshake message; a server that wants to restrict it replies on cistiertagger:restrict. It is opt-in: a server that ignores the handshake leaves the mod working normally, so vanilla servers are unaffected. Nothing needs to be installed server-side beyond your own plugin.

Packets

• cistiertagger:handshake - serverbound (client -> server), empty. The client sends it once it has joined; receiving it means that player runs the mod. This is the reliable way to detect the mod (channel-registration packets land in the configuration phase and are easy to miss).
• cistiertagger:restrict - clientbound (server -> client). Three booleans, one byte each (0 = show, 1 = hide), in order: nametag, tab, chat.

Behaviour

• Reply to the handshake with a restrict packet. Resend any time to change or lift the restriction.
• The client clears the restriction by itself on disconnect, so it only ever applies to the server that set it.
• On a restricting packet the client stops drawing the listed surfaces and prints a one-line chat notice whose hover lists which surfaces were disabled.

Implementation examples

Wait for the client's cistiertagger:handshake, then reply on cistiertagger:restrict. The byte order is always nametag, tab, chat; { 1, 1, 1 } hides everything, { 0, 0, 1 } only chat, { 0, 0, 0 } lifts it.

Bukkit

// onEnable()
getServer().getMessenger().registerOutgoingPluginChannel(this, "cistiertagger:restrict");
getServer().getMessenger().registerIncomingPluginChannel(this, "cistiertagger:handshake", new CisTierRestrictor());

import org.bukkit.entity.Player;
import org.bukkit.plugin.messaging.PluginMessageListener;

import static your.plugin.Main.plugin;

public class CisTierRestrictor implements PluginMessageListener {

    private static final String RESTRICT = "cistiertagger:restrict";

    @Override
    public void onPluginMessageReceived(String channel, Player player, byte[] message) {
        byte[] payload = { 1, 1, 1 }; // nametag, tab, chat
        player.sendPluginMessage(plugin, RESTRICT, payload);
    }
}

PacketEvents

// onEnable()
PacketEvents.getAPI().getEventManager().registerListener(new CisTierRestrictor(), PacketListenerPriority.NORMAL);

import com.github.retrooper.packetevents.event.PacketListener;
import com.github.retrooper.packetevents.event.PacketReceiveEvent;
import com.github.retrooper.packetevents.protocol.packettype.PacketType;
import com.github.retrooper.packetevents.wrapper.play.client.WrapperPlayClientPluginMessage;
import com.github.retrooper.packetevents.wrapper.play.server.WrapperPlayServerPluginMessage;

public class CisTierRestrictor implements PacketListener {

    private static final String HANDSHAKE = "cistiertagger:handshake";
    private static final String RESTRICT = "cistiertagger:restrict";

    @Override
    public void onPacketReceive(PacketReceiveEvent event) {
        if (event.getPacketType() != PacketType.Play.Client.PLUGIN_MESSAGE) return;

        WrapperPlayClientPluginMessage message = new WrapperPlayClientPluginMessage(event);
        if (!message.getChannelName().equals(HANDSHAKE)) return;

        byte[] payload = { 1, 1, 1 }; // nametag, tab, chat
        event.getUser().sendPacket(new WrapperPlayServerPluginMessage(RESTRICT, payload));
    }
}