(feat.) Check if the MongoDB port is open before binding to it

src/main/java/emu/lunarcore/database/DatabaseManager.java

@@ -2,6 +2,7 @@ package emu.lunarcore.database;
 
 import java.util.stream.Stream;
 
+import emu.lunarcore.util.Utils;
 import org.bson.codecs.configuration.CodecRegistries;
 import org.reflections.Reflections;
 
@@ -36,22 +37,23 @@ import lombok.Getter;
 public final class DatabaseManager {
     @Getter private static MongoServer server;
     private Datastore datastore;
-    
+
     private final DeleteOptions DELETE_MANY = new DeleteOptions().multi(true);
 
     public DatabaseManager(DatabaseInfo info, ServerType type) {
         // Variables
+        var internalConfig = LunarCore.getConfig().getInternalMongoServer();
         String connectionString = info.getUri();
 
         // Local mongo server
-        if (info.isUseInternal()) {
-            connectionString = startInternalMongoServer(LunarCore.getConfig().getInternalMongoServer());
+        if (info.isUseInternal() && Utils.isPortOpen(internalConfig.getAddress(), internalConfig.getPort())) {
+            connectionString = startInternalMongoServer(internalConfig);
             LunarCore.getLogger().info("Using local mongo server at " + server.getConnectionString());
         }
 
         // Initialize
         MongoClient gameMongoClient = MongoClients.create(connectionString);
-        
+
         // Add our custom fastutil codecs
         var codecProvider = CodecRegistries.fromCodecs(
                new IntSetCodec(), new Int2IntMapCodec()
@@ -76,13 +78,13 @@ public final class DatabaseManager {
                     return e != null && !e.value().equals(Mapper.IGNORED_FIELDNAME);
                 })
                 .toList();
-        
+
         if (type.runDispatch()) {
             // Only map account related entities
             var map = entities.stream().filter(cls -> {
                 return cls.getAnnotation(AccountDatabaseOnly.class) != null;
             }).toArray(Class<?>[]::new);
-            
+
             datastore.getMapper().map(map);
         }
         if (type.runGame()) {
@@ -90,7 +92,7 @@ public final class DatabaseManager {
             var map = entities.stream().filter(cls -> {
                 return cls.getAnnotation(AccountDatabaseOnly.class) == null;
             }).toArray(Class<?>[]::new);
-            
+
             datastore.getMapper().map(map);
         }
 
@@ -171,7 +173,7 @@ public final class DatabaseManager {
             getDatastore().save(counter);
         }
     }
-    
+
     // Internal MongoDB server
 
     public static String startInternalMongoServer(InternalMongoInfo internalMongo) {

src/main/java/emu/lunarcore/util/Utils.java

@@ -1,6 +1,10 @@
 package emu.lunarcore.util;
 
 import java.io.File;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
 import java.util.Base64;
 import java.util.List;
 import java.util.concurrent.ThreadLocalRandom;
@@ -75,7 +79,7 @@ public class Utils {
     public static long getCurrentSeconds() {
         return Math.floorDiv(System.currentTimeMillis(), 1000);
     }
-    
+
     public static int getMinPromotionForLevel(int level) {
         return Math.max(Math.min((int) ((level - 11) / 10D), 6), 0);
     }
@@ -84,7 +88,7 @@ public class Utils {
         if (s == null) {
             return 0;
         }
-        
+
         int i = 0;
 
         try {
@@ -100,7 +104,7 @@ public class Utils {
         if (s == null) {
             return 0;
         }
-        
+
         long i = 0;
 
         try {
@@ -127,7 +131,7 @@ public class Utils {
     public static <T> T randomElement(List<T> list) {
         return list.get(ThreadLocalRandom.current().nextInt(0, list.size()));
     }
-    
+
     /**
      * Checks if an integer array contains a value
      * @param array
@@ -135,7 +139,7 @@ public class Utils {
      */
     public static boolean arrayContains(int[] array, int value) {
         for (int i = 0; i < array.length; i++) {
-            if (array[i] == value) return true; 
+            if (array[i] == value) return true;
         }
         return false;
     }
@@ -157,4 +161,21 @@ public class Utils {
     public static byte[] base64Decode(String toDecode) {
         return Base64.getDecoder().decode(toDecode);
     }
+
+    /**
+     * Checks if a port is open on a given host.
+     *
+     * @param host The host to check.
+     * @param port The port to check.
+     * @return True if the port is open, false otherwise.
+     */
+    public static boolean isPortOpen(String host, int port) {
+        try (var serverSocket = new ServerSocket()) {
+            serverSocket.setReuseAddress(false);
+            serverSocket.bind(new InetSocketAddress(InetAddress.getByName(host), port), 1);
+            return true;
+        } catch (Exception ex) {
+            return false;
+        }
+    }
 }