Created a network packet for when a client presses a key. (Mod is now also client sided). Renamed some event handlers. Made it so after a client presses a key their grace period starts. After the grace period ends the player is removed from the list.

src/main/java/com/micle/loginprotection/LoginProtection.java

@@ -13,6 +13,7 @@ import java.util.List;
 public class LoginProtection {
     public static final String MOD_ID = "loginprotection";
     public static ProtectedPlayers protected_players = new ProtectedPlayers();
+    public static boolean has_pressed_key = false;
 
     public LoginProtection() {
         Registration.register();

src/main/java/com/micle/loginprotection/data/ProtectedPlayers.java

@@ -9,6 +9,10 @@ public class ProtectedPlayers {
 
     public ProtectedPlayers() { }
 
+    public int size() {
+        return protected_players.size();
+    }
+
     public void addPlayer(UUID player_uuid) {
         protected_players.add(new ProtectedPlayer(player_uuid));
     }
@@ -23,4 +27,21 @@ public class ProtectedPlayers {
         }
         return player;
     }
+
+    public void removePlayer(UUID player_uuid) {
+        ProtectedPlayer player = getPlayer(player_uuid);
+        if (player == null) { return; }
+        protected_players.remove(player);
+    }
+
+    public void updateGracePeriods() {
+        for (ProtectedPlayer protected_player : protected_players) {
+            if (protected_player.isLoading() || protected_player.getGracePeriod() <= 0) { continue; }
+            int grace_period = protected_player.getGracePeriod();
+            protected_player.setGracePeriod(grace_period-1);
+            if (grace_period <= 0) {
+                removePlayer(protected_player.getPlayerUUID());
+            }
+        }
+    }
 }

src/main/java/com/micle/loginprotection/events/OnKeyPressEventHandler.java

@@ -0,0 +1,13 @@
+package com.micle.loginprotection.events;
+
+import com.micle.loginprotection.LoginProtection;
+import net.minecraftforge.client.event.InputEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+
+public class OnKeyPressEventHandler {
+    @SubscribeEvent
+    public void KeyPressEvent(InputEvent.KeyInputEvent event) {
+        if (LoginProtection.has_pressed_key) { return; }
+
+    }
+}

src/main/java/com/micle/loginprotection/events/OnPlayerDamageEventHandler.java

@@ -5,7 +5,7 @@ import net.minecraft.entity.player.PlayerEntity;
 import net.minecraftforge.eventbus.api.SubscribeEvent;
 import net.minecraftforge.event.entity.living.LivingDamageEvent;
 
-public class OnEntityDamageEventHandler {
+public class OnPlayerDamageEventHandler {
     @SubscribeEvent
     public void LivingDamageEvent(LivingDamageEvent event) {
         if (!(event.getEntity() instanceof PlayerEntity)) { return; }

src/main/java/com/micle/loginprotection/events/OnPlayerJoinEventHandler.java

@@ -7,7 +7,7 @@ import net.minecraft.entity.player.PlayerEntity;
 import net.minecraftforge.event.entity.EntityJoinWorldEvent;
 import net.minecraftforge.eventbus.api.SubscribeEvent;
 
-public class OnEntityJoinEventHandler {
+public class OnPlayerJoinEventHandler {
     @SubscribeEvent
     public void EntityJoinWorldEvent(EntityJoinWorldEvent event) {
         if (!(event.getEntity() instanceof PlayerEntity)) { return; }

src/main/java/com/micle/loginprotection/events/OnServerTickEventHandler.java

@@ -0,0 +1,14 @@
+package com.micle.loginprotection.events;
+
+import com.micle.loginprotection.LoginProtection;
+import net.minecraftforge.event.TickEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+
+public class OnServerTickEventHandler {
+    @SubscribeEvent
+    public void ServerTickEvent(TickEvent.ServerTickEvent event) {
+        if (LoginProtection.protected_players.size() == 0) { return; }
+
+        LoginProtection.protected_players.updateGracePeriods();
+    }
+}

src/main/java/com/micle/loginprotection/network/C2SKeyPress.java

@@ -0,0 +1,29 @@
+package com.micle.loginprotection.network;
+
+import com.micle.loginprotection.LoginProtection;
+import net.minecraft.entity.player.ServerPlayerEntity;
+import net.minecraft.network.PacketBuffer;
+import net.minecraftforge.fml.network.NetworkEvent;
+
+import java.util.function.Supplier;
+
+public class C2SKeyPress {
+    public C2SKeyPress() { }
+
+    public static void encode(final C2SKeyPress msg, final PacketBuffer packet_buffer) { }
+
+    public static C2SKeyPress decode(final PacketBuffer packet_buffer) {
+        return new C2SKeyPress();
+    }
+
+    public static void handle(final C2SKeyPress msg, final Supplier<NetworkEvent.Context> context_supplier) {
+        final NetworkEvent.Context context = context_supplier.get();
+        context.enqueueWork(() -> {
+            final ServerPlayerEntity sender = context.getSender();
+            if (sender == null) { return; }
+
+            LoginProtection.protected_players.getPlayer(sender.getUUID()).setLoading(false);
+        });
+        context.setPacketHandled(true);
+    }
+}

src/main/java/com/micle/loginprotection/setup/Registration.java

@@ -1,16 +1,37 @@
 package com.micle.loginprotection.setup;
 
-import com.micle.loginprotection.events.OnEntityDamageEventHandler;
-import com.micle.loginprotection.events.OnEntityJoinEventHandler;
+import com.micle.loginprotection.LoginProtection;
+import com.micle.loginprotection.events.OnPlayerDamageEventHandler;
+import com.micle.loginprotection.events.OnPlayerJoinEventHandler;
+import com.micle.loginprotection.network.C2SKeyPress;
+import net.minecraft.util.ResourceLocation;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.eventbus.api.IEventBus;
 import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
+import net.minecraftforge.fml.network.NetworkRegistry;
+import net.minecraftforge.fml.network.simple.SimpleChannel;
 
 public class Registration {
+    private static final String PROTOCOL_VERSION = "1";
+    public static final SimpleChannel INSTANCE = NetworkRegistry.newSimpleChannel(
+            new ResourceLocation(LoginProtection.MOD_ID, "main"),
+            () -> PROTOCOL_VERSION,
+            PROTOCOL_VERSION::equals,
+            PROTOCOL_VERSION::equals
+    );
+
     public static void register() {
         IEventBus mod_event_bus = FMLJavaModLoadingContext.get().getModEventBus();
 
-        MinecraftForge.EVENT_BUS.register(new OnEntityJoinEventHandler());
-        MinecraftForge.EVENT_BUS.register(new OnEntityDamageEventHandler());
+        MinecraftForge.EVENT_BUS.register(new OnPlayerJoinEventHandler());
+        MinecraftForge.EVENT_BUS.register(new OnPlayerDamageEventHandler());
+
+        int id = 0;
+        INSTANCE.registerMessage(id++,
+                C2SKeyPress.class,
+                C2SKeyPress::encode,
+                C2SKeyPress::decode,
+                C2SKeyPress::handle
+        );
     }
 }