More descriptive disconnect messages for outdated Java servers

core/src/main/java/org/geysermc/connector/network/session/GeyserSession.java

@@ -100,7 +100,7 @@ public class GeyserSession {
     }
 
     public void login() {
-        this.handle.login();
+        throw new UnsupportedOperationException();
     }
 
     public void authenticate(String username) {
@@ -120,7 +120,7 @@ public class GeyserSession {
     }
 
     public void close() {
-        this.handle.close();
+        throw new UnsupportedOperationException();
     }
 
     public void executeInEventLoop(Runnable runnable) {

core/src/main/java/org/geysermc/geyser/session/GeyserSession.java

@@ -625,17 +625,6 @@ public class GeyserSession implements GeyserConnection, CommandSender {
         upstream.sendPacket(gamerulePacket);
     }
 
-    public void login() {
-        if (this.remoteAuthType != AuthType.ONLINE) {
-            if (this.remoteAuthType == AuthType.OFFLINE) {
-                geyser.getLogger().info(GeyserLocale.getLocaleStringLog("geyser.auth.login.offline"));
-            } else {
-                geyser.getLogger().info(GeyserLocale.getLocaleStringLog("geyser.auth.login.floodgate"));
-            }
-            authenticate(authData.name());
-        }
-    }
-
     public void authenticate(String username) {
         authenticate(username, "");
     }
@@ -1046,10 +1035,6 @@ public class GeyserSession implements GeyserConnection, CommandSender {
         closed = true;
     }
 
-    public void close() {
-        disconnect(GeyserLocale.getPlayerLocaleString("geyser.network.close", getClientData().getLanguageCode()));
-    }
-
     /**
      * Executes a task and prints a stack trace if an error occurs.
      */

core/src/main/java/org/geysermc/geyser/translator/protocol/java/JavaLoginDisconnectTranslator.java

@@ -26,7 +26,13 @@
 package org.geysermc.geyser.translator.protocol.java;
 
 import com.github.steveice10.mc.protocol.packet.login.clientbound.ClientboundLoginDisconnectPacket;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.TextComponent;
+import net.kyori.adventure.text.TranslatableComponent;
+import org.geysermc.common.PlatformType;
+import org.geysermc.geyser.network.MinecraftProtocol;
 import org.geysermc.geyser.session.GeyserSession;
+import org.geysermc.geyser.text.GeyserLocale;
 import org.geysermc.geyser.translator.protocol.PacketTranslator;
 import org.geysermc.geyser.translator.protocol.Translator;
 import org.geysermc.geyser.translator.text.MessageTranslator;
@@ -36,8 +42,37 @@ public class JavaLoginDisconnectTranslator extends PacketTranslator<ClientboundL
 
     @Override
     public void translate(GeyserSession session, ClientboundLoginDisconnectPacket packet) {
+        Component disconnectReason = packet.getReason();
+
+        boolean isOutdatedMessage;
+        if (disconnectReason instanceof TranslatableComponent component) {
+            String key = component.key();
+            isOutdatedMessage = "multiplayer.disconnect.incompatible".equals(key) ||
+                    // Legacy string (starting from at least 1.15.2)
+                    "multiplayer.disconnect.outdated_server".equals(key)
+                    // Reproduced on 1.15.2 server with ViaVersion 4.0.0-21w20a with 1.18.2 Java client
+                    || key.startsWith("Outdated server!");
+        } else {
+            // Reproduced with vanilla 1.8.8 server and 1.18.2 Java client
+            isOutdatedMessage = disconnectReason instanceof TextComponent component
+                    && component.content().startsWith("Outdated server!");
+        }
+
+        String serverDisconnectMessage = MessageTranslator.convertMessage(disconnectReason, session.getLocale());
+        String disconnectMessage;
+        if (isOutdatedMessage) {
+            String locale = session.getLocale();
+            PlatformType platform = session.getGeyser().getPlatformType();
+            String outdatedType = (platform == PlatformType.BUNGEECORD || platform == PlatformType.VELOCITY) ?
+                    "geyser.network.remote.outdated.proxy" : "geyser.network.remote.outdated.server";
+            disconnectMessage = GeyserLocale.getPlayerLocaleString(outdatedType, locale, MinecraftProtocol.getJavaVersions().get(0)) + '\n'
+                    + GeyserLocale.getPlayerLocaleString("geyser.network.remote.original_disconnect_message", locale, serverDisconnectMessage);
+        } else {
+            disconnectMessage = serverDisconnectMessage;
+        }
+
         // The client doesn't manually get disconnected so we have to do it ourselves
-        session.disconnect(MessageTranslator.convertMessage(packet.getReason(), session.getLocale()));
+        session.disconnect(disconnectMessage);
     }
 
     @Override