Support port checkers

NitroxServer/Communication/LiteNetLib/LiteNetLibServer.cs

@@ -1,4 +1,4 @@
-using System.Buffers;
+using System.Buffers;
 using System.Threading;
 using System.Threading.Tasks;
 using LiteNetLib;
@@ -21,7 +21,7 @@ public class LiteNetLibServer : NitroxServer
     public LiteNetLibServer(PacketHandler packetHandler, PlayerManager playerManager, EntitySimulation entitySimulation, ServerConfig serverConfig) : base(packetHandler, playerManager, entitySimulation, serverConfig)
     {
         listener = new EventBasedNetListener();
-        server = new NetManager(listener);
+        server = new NetManager(listener, new PortCheckerSupport());
     }
 
     public override bool Start()

NitroxServer/Communication/LiteNetLib/PortCheckerSupport.cs

@@ -0,0 +1,30 @@
+using System.Net;
+using LiteNetLib.Layers;
+using System.Net.Sockets;
+namespace NitroxServer.Communication.LiteNetLib;
+
+public class PortCheckerSupport : PacketLayerBase
+{
+    public static bool active;
+    private readonly UdpClient udpClient = new();
+    public PortCheckerSupport() : base(0)
+    {
+        active = false;
+    }
+
+    public override void ProcessInboundPacket(ref IPEndPoint endPoint, ref byte[] data, ref int length)
+    {
+        if (active)
+        {
+            Log.Warn("WARNING: Port Checker must be disabled to allow players to join the server");
+            byte[] datacopy = (byte[])data.Clone();
+            length = 0; // Set length to 0 so NetManager stops processing packet immediately
+            udpClient.Send(datacopy, datacopy.Length, endPoint);
+        }
+
+    }
+    public override void ProcessOutBoundPacket(ref IPEndPoint endPoint, ref byte[] data, ref int offset, ref int length)
+    {
+
+    }
+}

NitroxServer/ConsoleCommands/PortCheckerToggleCommand.cs

@@ -0,0 +1,20 @@
+using LiteNetLib;
+using NitroxModel.DataStructures.GameLogic;
+using NitroxServer.Communication.LiteNetLib;
+using NitroxServer.ConsoleCommands.Abstract;
+using NitroxServer.ConsoleCommands.Abstract.Type;
+
+namespace NitroxServer.ConsoleCommands;
+public class PortCheckerToggleCommand : Command
+{
+    public PortCheckerToggleCommand() : base("toggleportchecker", Perms.CONSOLE, "Enable/Disable the port forwarding tester")
+    {
+
+    }
+
+    protected override void Execute(CallArgs args)
+    {
+        PortCheckerSupport.active = !PortCheckerSupport.active;
+        Log.Info("Togggled port checker " + PortCheckerSupport.active);
+    }
+}