Added "Logged in from another location" protection.

gradle.properties

@@ -2,12 +2,12 @@
 org.gradle.jvmargs=-Xmx1G
 
 # Fabric properties
-minecraft_version=20w15a
+minecraft_version=20w16a
-yarn_mappings=20w15a+build.1
+yarn_mappings=20w16a+build.1
 loader_version=0.8.2+build.194
 
 #Fabric api
-fabric_version=0.5.9+build.319-1.16
+fabric_version=0.5.10+build.320-1.16
 
 # Mod Properties
 	mod_version = 1.3.3

src/main/java/org/samo_lego/simpleauth/SimpleAuth.java

@@ -110,7 +110,7 @@ public class SimpleAuth implements DedicatedServerModInitializer {
 		// Player no longer needs to be invisible and invulnerable
 		player.setInvulnerable(false);
 		player.setInvisible(false);
-		player.sendMessage(msg);
+		player.sendMessage(msg, false);
 	}
 
 	// De-authenticates player
@@ -120,10 +120,10 @@ public class SimpleAuth implements DedicatedServerModInitializer {
 		SimpleAuth.deauthenticatedUsers.put(uuid, new PlayerCache(uuid, player.getIp()));
 
 		// Player is now not authenticated
-		player.sendMessage(notAuthenticated());
+		player.sendMessage(notAuthenticated(), false);
 		// Setting the player to be invisible to mobs and also invulnerable
-		player.setInvulnerable(SimpleAuth.config.main.playerInvulnerable);
+		player.setInvulnerable(SimpleAuth.config.experimental.playerInvulnerable);
-		player.setInvisible(SimpleAuth.config.main.playerInvisible);
+		player.setInvisible(SimpleAuth.config.experimental.playerInvisible);
 		Timer timer = new Timer();
 		timer.schedule(new TimerTask() {
 			@Override

src/main/java/org/samo_lego/simpleauth/mixin/MixinServerLoginNetworkHandler.java

@@ -0,0 +1,43 @@
+package org.samo_lego.simpleauth.mixin;
+
+import com.mojang.authlib.GameProfile;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.network.ServerLoginNetworkHandler;
+import net.minecraft.text.LiteralText;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import static org.samo_lego.simpleauth.SimpleAuth.config;
+
+
+@Mixin(ServerLoginNetworkHandler.class)
+public abstract class MixinServerLoginNetworkHandler {
+
+    @Shadow @Final
+    private MinecraftServer server;
+
+    @Shadow
+    private GameProfile profile;
+
+    @Inject(method = "acceptPlayer()V", at = @At("HEAD"), cancellable = true)
+    private void acceptPlayer(CallbackInfo ci) {
+        //  Player pre-join event, we don't do standard callback, since
+        // there are lots of variables that would need to be passed over
+        PlayerEntity onlinePlayer = this.server.getPlayerManager().getPlayer(this.profile.getName());
+
+        // Getting network handler
+        ServerLoginNetworkHandler handler = (ServerLoginNetworkHandler) (Object) this;
+
+        if (config.experimental.disableAnotherLocationKick && onlinePlayer != null) {
+            // Player needs to be kicked, since there's already a player with that name
+            // playing on the server
+            handler.disconnect(new LiteralText(String.format(config.lang.playerAlreadyOnline, onlinePlayer.getName().asString())));
+            ci.cancel();
+        }
+    }
+}

src/main/java/org/samo_lego/simpleauth/storage/AuthConfig.java

@@ -30,28 +30,8 @@ import java.io.IOException;
 public class AuthConfig {
     // If player is not authenticated, following conditions apply
     public static class MainConfig {
-        // Allows chat (but not commands, except for /login and /register)
+        // Allows "right-clicking" on an entity (e.g. clicking on villagers)
-        public boolean allowChat = false;
-        // Allows player movement
-        public boolean allowMovement = false;
-        // Allows block "use" - right clicking (e.g. opening a chest)
-        public boolean allowBlockUse = false;
-        // Allows mining || punching blocks
-        public boolean allowBlockPunch = false;
-        // Allows dropping items from inventory
-        public boolean allowItemDrop = false;
-        // Allows moving item through inventory
-        public boolean allowItemMoving = false;
-        // Allows item "use" - right click function (e.g. using a bow)
-        public boolean allowItemUse = false;
-        // Allows attacking mobs
-        public boolean allowEntityPunch = false;
-        // Allows "right-clicking" on an entity (e.g. trading with villagers)
         public boolean allowEntityInteract = false;
-        // If player should be invulnerable before authentication
-        public boolean playerInvulnerable = true;
-        // If player should be invisible to mobs before authentication
-        public boolean playerInvisible = true;
         // Maximum login tries before kicking the player from server
         // Set to -1 to allow unlimited, not recommended however
         public int maxLoginTries = 1;
@@ -102,6 +82,31 @@ public class AuthConfig {
         public String maxPasswordChars = "§6Password can be at most %d characters long!";
         public String minPasswordChars = "§6Password needs to be at least %d characters long!";
         public String disallowedUsername = "§6Invalid username characters! Allowed character regex: %s";
+        public String playerAlreadyOnline = "§cPlayer %s is already online!";
+    }
+    public static class ExperimentalConfig {
+        // Prevents player being kicked because another player with the same name has joined the server
+        public boolean disableAnotherLocationKick = true;
+        // If player should be invulnerable before authentication
+        public boolean playerInvulnerable = true;
+        // If player should be invisible to mobs before authentication
+        public boolean playerInvisible = true;
+        // Allows chat (but not commands, except for /login and /register)
+        public boolean allowChat = false;
+        // Allows player movement
+        public boolean allowMovement = false;
+        // Allows block "use" - right clicking (e.g. opening a chest)
+        public boolean allowBlockUse = false;
+        // Allows mining || punching blocks
+        public boolean allowBlockPunch = false;
+        // Allows dropping items from inventory
+        public boolean allowItemDrop = false;
+        // Allows moving item through inventory
+        public boolean allowItemMoving = false;
+        // Allows item "use" - right click function (e.g. using a bow)
+        public boolean allowItemUse = false;
+        // Allows attacking mobs
+        public boolean allowEntityPunch = false;
     }
     private static final Logger LOGGER = LogManager.getLogger();
     private static final Gson gson = new GsonBuilder()
@@ -110,6 +115,7 @@ public class AuthConfig {
 
     public MainConfig main = new MainConfig();
     public LangConfig lang = new LangConfig();
+    public ExperimentalConfig experimental = new ExperimentalConfig();
 
     public static AuthConfig load(File file) {
         AuthConfig config;

src/main/resources/mixins.simpleauth.json

@@ -5,9 +5,10 @@
   "mixins": [
   ],
   "server": [
-    "MixinServerPlayNetworkHandler",
-    "MixinPlayerManager",
     "MixinPlayerEntity",
+    "MixinPlayerManager",
+    "MixinServerLoginNetworkHandler",
+    "MixinServerPlayNetworkHandler",
     "MixinSlot"
   ],
   "injectors": {