Add `PlayerConnection#flush` without guarantee

src/main/java/net/minestom/server/UpdateManager.java

@@ -7,7 +7,6 @@ import net.minestom.server.instance.Instance;
 import net.minestom.server.instance.InstanceManager;
 import net.minestom.server.monitoring.TickMonitor;
 import net.minestom.server.network.ConnectionManager;
-import net.minestom.server.network.player.PlayerSocketConnection;
 import net.minestom.server.thread.SingleThreadProvider;
 import net.minestom.server.thread.ThreadProvider;
 import org.jetbrains.annotations.NotNull;
@@ -83,10 +82,7 @@ public final class UpdateManager {
 
                     // Flush all waiting packets
                     for (Player player : connectionManager.getOnlinePlayers()) {
-                        final var connection = player.getPlayerConnection();
-                        if (connection instanceof PlayerSocketConnection) {
-                            ((PlayerSocketConnection) connection).flush();
-                        }
+                        player.getPlayerConnection().flush();
                     }
 
                     // Disable thread until next tick

src/main/java/net/minestom/server/entity/Player.java

@@ -571,9 +571,7 @@ public class Player extends LivingEntity implements CommandSender, Localizable,
         PlayerSpawnEvent spawnEvent = new PlayerSpawnEvent(this, instance, firstSpawn);
         EventDispatcher.call(spawnEvent);
 
-        if (playerConnection instanceof PlayerSocketConnection) {
-            ((PlayerSocketConnection) playerConnection).flush();
-        }
+        this.playerConnection.flush();
     }
 
     /**

src/main/java/net/minestom/server/network/ConnectionManager.java

@@ -293,9 +293,7 @@ public final class ConnectionManager {
             EventDispatcher.call(asyncPlayerPreLoginEvent);
             // Close the player channel if he has been disconnected (kick)
             if (!player.isOnline()) {
-                if (playerConnection instanceof PlayerSocketConnection) {
-                    ((PlayerSocketConnection) playerConnection).flush();
-                }
+                playerConnection.flush();
                 //playerConnection.disconnect();
                 return;
             }

src/main/java/net/minestom/server/network/player/PlayerConnection.java

@@ -50,9 +50,8 @@ public abstract class PlayerConnection {
             if (tickCounter % MinecraftServer.TICK_PER_SECOND == 0 && tickCounter > 0) {
                 tickCounter = 0;
                 // Retrieve the packet count
-                final int count = packetCounter.get();
+                final int count = packetCounter.getAndSet(0);
                 this.lastPacketCounter.set(count);
-                this.packetCounter.set(0);
                 if (count > MinecraftServer.getRateLimit()) {
                     // Sent too many packets
                     player.kick(rateLimitKickMessage);
@@ -101,6 +100,15 @@ public abstract class PlayerConnection {
      */
     public abstract void sendPacket(@NotNull ServerPacket serverPacket, boolean skipTranslating);
 
+    /**
+     * Flush waiting data to the connection.
+     * <p>
+     * Might not do anything depending on the implementation.
+     */
+    public void flush() {
+        // Empty
+    }
+
     protected boolean shouldSendPacket(@NotNull ServerPacket serverPacket) {
         return player == null ||
                 PACKET_LISTENER_MANAGER.processServerPacket(serverPacket, Collections.singleton(player));

src/main/java/net/minestom/server/network/player/PlayerSocketConnection.java

@@ -252,6 +252,7 @@ public class PlayerSocketConnection extends PlayerConnection {
         }
     }
 
+    @Override
     public void flush() {
         if (!channel.isOpen()) return;
         synchronized (tickBuffer) {