Reintroduce proper multiplayer

- Can now re-open singleplayer server
  so other players can join over internet
- Multiplayer menu supports all this
- Fix issue where players would also
  send other players' position as RPCs

scene/GameScene.tscn

@@ -11,6 +11,5 @@ BlockContainerPath = NodePath("World/Blocks")
 [node name="World" type="Node" parent="."]
 
 [node name="Players" type="Node" parent="World"]
-pause_mode = 1
 
 [node name="Blocks" type="Node" parent="World"]

src/EscapeMenuAppearance.cs

@@ -20,7 +20,7 @@ public class EscapeMenuAppearance : CenterContainer
         ColorSlider.Value = GD.Randf();
         ColorPreview.Modulate = Color.FromHsv((float)ColorSlider.Value, 1.0F, 1.0F);
 
-        this.GetClient().OnConnected += () =>
+        this.GetClient().Connected += () =>
             this.GetClient().RPC(Player.ChangeAppearance, DisplayName.Text, ColorPreview.Modulate);
     }
 
@@ -50,7 +50,7 @@ public class EscapeMenuAppearance : CenterContainer
         if (IsVisibleInTree()) return;
         var client = this.GetClient();
         // TODO: Find a better way to know if we're connected?
-        if (client.CustomMultiplayer.NetworkPeer?.GetConnectionStatus() == NetworkedMultiplayerPeer.ConnectionStatus.Connected)
+        if (client.Status == NetworkedMultiplayerPeer.ConnectionStatus.Connected)
             client.RPC(Player.ChangeAppearance, DisplayName.Text, ColorPreview.Modulate);
     }
 }

src/EscapeMenuMultiplayer.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Text.RegularExpressions;
 using Godot;
+using static Godot.NetworkedMultiplayerPeer;
 
 public class EscapeMenuMultiplayer : Container
 {
@@ -17,7 +19,7 @@ public class EscapeMenuMultiplayer : Container
     public Button ClientDisConnect { get; private set; }
     public LineEdit ClientAddress { get; private set; }
 
-    public IntegratedServer Server { get; private set; }
+    public IntegratedServer IntegratedServer { get; private set; }
 
     public override void _Ready()
     {
@@ -30,54 +32,57 @@ public class EscapeMenuMultiplayer : Container
         ServerPort.PlaceholderText    = DEFAULT_PORT.ToString();
         ClientAddress.PlaceholderText = $"localhost:{DEFAULT_PORT}";
 
+        this.GetClient().StatusChanged += OnStatusChanged;
         CallDeferred(nameof(SetupIntegratedServer));
     }
     private void SetupIntegratedServer()
     {
-        Server = new IntegratedServer();
-        this.GetClient().AddChild(Server);
+        IntegratedServer = new IntegratedServer();
+        this.GetClient().AddChild(IntegratedServer);
         CallDeferred(nameof(StartIntegratedServerAndConnect));
     }
     private void StartIntegratedServerAndConnect()
     {
-        Server.Start(DEFAULT_PORT);
-        this.GetClient().Connect("localhost", DEFAULT_PORT);
+        var port = IntegratedServer.Server.StartSingleplayer();
+        this.GetClient().Connect("127.0.0.1", port);
     }
 
+    private void OnStatusChanged(ConnectionStatus status)
+    {
+        switch (status) {
+            case ConnectionStatus.Disconnected:
+                Status.Text     = "Disconnected";
+                Status.Modulate = Colors.Red;
+                break;
+            case ConnectionStatus.Connecting:
+                Status.Text     = "Connecting ...";
+                Status.Modulate = Colors.Yellow;
+                break;
+            case ConnectionStatus.Connected:
+                if (IntegratedServer == null) {
+                    Status.Text     = "Connected!";
+                    Status.Modulate = Colors.Green;
+                } else if (IntegratedServer.Server.IsSingleplayer) {
+                    Status.Text     = "Singleplayer";
+                    Status.Modulate = Colors.White;
+                } else {
+                    Status.Text     = "Server Running";
+                    Status.Modulate = Colors.Green;
+                }
+                break;
+        }
+
+        ServerPort.Editable      = IntegratedServer != null;
+        ServerOpenClose.Disabled = IntegratedServer == null;
+        ServerOpenClose.Text     = (IntegratedServer?.Server.IsSingleplayer == false) ? "Close Server" : "Open Server";
+        ClientDisConnect.Text = ((IntegratedServer != null) || (status == ConnectionStatus.Disconnected)) ? "Connect" : "Disconnect";
 
-    // private void OnNetworkStatusChanged(NetworkStatus status)
-    // {
-    //     switch (status) {
-    //         case NetworkStatus.NoConnection:
-    //             Status.Text     = "No Connection";
-    //             Status.Modulate = Colors.Red;
-    //             break;
-    //         case NetworkStatus.ServerRunning:
-    //             Status.Text     = "Server Running";
-    //             Status.Modulate = Colors.Green;
-    //             break;
-    //         case NetworkStatus.Connecting:
-    //             Status.Text     = "Connecting ...";
-    //             Status.Modulate = Colors.Yellow;
-    //             break;
-    //         case NetworkStatus.Authenticating:
-    //             Status.Text     = "Authenticating ...";
-    //             Status.Modulate = Colors.YellowGreen;
-    //             break;
-    //         case NetworkStatus.ConnectedToServer:
-    //             Status.Text     = "Connected to Server";
-    //             Status.Modulate = Colors.Green;
-    //             break;
-    //     }
-
-    //     var noConnection = status == NetworkStatus.NoConnection;
-    //     ServerPort.Editable = noConnection;
-    //     ServerOpenClose.Text     = (status == NetworkStatus.ServerRunning) ? "Stop Server" : "Start Server";
-    //     ServerOpenClose.Disabled = status > NetworkStatus.ServerRunning;
-    //     ClientAddress.Editable = noConnection;
-    //     ClientDisConnect.Text     = (status < NetworkStatus.Connecting) ? "Connect" : "Disconnect";
-    //     ClientDisConnect.Disabled = status == NetworkStatus.ServerRunning;
-    // }
+        var pauseMode = (IntegratedServer?.Server.IsSingleplayer == true) ? PauseModeEnum.Stop : PauseModeEnum.Process;
+        this.GetClient().GetNode("World").PauseMode = pauseMode;
+        if (IntegratedServer != null) IntegratedServer.Server.GetNode("World").PauseMode = pauseMode;
+
+        // TODO: Allow starting up the integrated server again when disconnected.
+    }
 
 
     #pragma warning disable IDE0051
@@ -95,32 +100,62 @@ public class EscapeMenuMultiplayer : Container
         }
     }
 
+    private void _on_HideAddress_toggled(bool pressed)
+        => ClientAddress.Secret = pressed;
+
 
     private void _on_ServerOpenClose_pressed()
     {
-        // if (GetTree().NetworkPeer == null) {
-        //     var port = Network.DEFAULT_PORT;
-        //     if (ServerPort.Text.Length > 0)
-        //         port = ushort.Parse(ServerPort.Text);
-        //     Network.Instance.StartServer(port);
-        // } else Network.Instance.StopServer();
+        var server = IntegratedServer?.Server;
+        var client = this.GetClient();
+        if (server?.IsRunning != true) throw new InvalidOperationException();
+
+        if (server.IsSingleplayer) {
+            var port = (ServerPort.Text.Length > 0) ? ushort.Parse(ServerPort.Text) : DEFAULT_PORT;
+            client.Disconnect();
+            server.Stop();
+            server.Start(port);
+            client.Connect("127.0.0.1", port);
+            // TODO: Pause server processing (including packets, RPC, Sync) until client reconnects?
+            //       If we're doing that, also make sure to re-map packet and RPC targets to point to new NetworkID.
+        } else {
+            client.Disconnect();
+            server.Stop();
+            var port = server.StartSingleplayer();
+            client.Connect("127.0.0.1", port);
+        }
+
+        ServerOpenClose.Text = server.IsSingleplayer ? "Open Server" : "Close Server";
+
     }
 
     private void _on_ClientDisConnect_pressed()
     {
-        // if (GetTree().NetworkPeer == null) {
-        //     var address = "localhost";
-        //     var port    = DEFAULT_PORT;
-        //     if (ClientAddress.Text.Length > 0) {
-        //         // TODO: Verify input some more, support IPv6?
-        //         var split = ClientAddress.Text.Split(':');
-        //         address = (split.Length > 1) ? split[0] : ClientAddress.Text;
-        //         port    = (split.Length > 1) ? ushort.Parse(split[1]) : port;
-        //     }
-        //     Network.Instance.ConnectToServer(address, port);
-        // } else Network.Instance.DisconnectFromServer();
-    }
+        var client = this.GetClient();
 
-    private void _on_HideAddress_toggled(bool pressed)
-        => ClientAddress.Secret = pressed;
+        if (IntegratedServer != null) {
+            IntegratedServer.Server.Stop();
+            IntegratedServer.GetParent().RemoveChild(IntegratedServer);
+            IntegratedServer.QueueFree();
+            IntegratedServer = null;
+
+            client.Disconnect();
+            NetworkSync.ClearAllObjects();
+        }
+
+        if (client.Status == ConnectionStatus.Disconnected) {
+            var address = "localhost";
+            var port    = DEFAULT_PORT;
+            if (ClientAddress.Text.Length > 0) {
+                // TODO: Verify input some more, support IPv6?
+                var split = ClientAddress.Text.Split(':');
+                address = (split.Length > 1) ? split[0] : ClientAddress.Text;
+                port    = (split.Length > 1) ? ushort.Parse(split[1]) : port;
+            }
+            client.Connect(address, port);
+        } else {
+            client.Disconnect();
+            NetworkSync.ClearAllObjects();
+        }
+    }
 }

src/Network/DeSerializer.Impl.cs

@@ -184,12 +184,12 @@ public class DictionaryDeSerializerGenerator
         private readonly IDeSerializer _valueDeSerializer =
             DeSerializerRegistry.Get<TKey>(true);
 
-        public override void Serialize(Game game, BinaryWriter writer, TDictionary value)
+        public override void Serialize(Game game, BinaryWriter writer, TDictionary dict)
         {
-            writer.Write(value.Count);
-            foreach (var element in value) {
-                _keyDeSerializer.Serialize(game, writer, element.Key);
-                _valueDeSerializer.Serialize(game, writer, element.Value);
+            writer.Write(dict.Count);
+            foreach (var (key, value) in dict) {
+                _keyDeSerializer.Serialize(game, writer, key);
+                _valueDeSerializer.Serialize(game, writer, value);
             }
         }
 
@@ -222,7 +222,12 @@ public class SyncedObjectDeSerializerGenerator
         public override void Serialize(Game game, BinaryWriter writer, TObj value)
             => writer.Write(value.GetSyncID());
         public override TObj Deserialize(Game game, BinaryReader reader)
-            => (TObj)game.GetObjectBySyncID(reader.ReadUInt32());
+        {
+            var id    = reader.ReadUInt32();
+            var value = (TObj)game.GetObjectBySyncID(id);
+            if (value == null) throw new Exception($"Could not find synced object of type {typeof(TObj)} with ID {id}");
+            return value;
+        }
     }
 }
 

src/Network/IntegratedServer.cs

@@ -16,12 +16,16 @@ public class IntegratedServer : Node
         _sceneTree.CurrentScene = scene;
 
         Server = _sceneTree.Root.GetChild<Server>(0);
+        // Spawn default blocks.
+        for (var x = -6; x <= 6; x++) {
+            var block = Server.Spawn<Block>();
+            block.Position    = new BlockPos(x, 3);
+            block.Color       = Color.FromHsv(GD.Randf(), 0.1F, 1.0F);
+            block.Unbreakable = true;
+        }
     }
 
     public override void _Process(float delta) => _sceneTree.Idle(delta);
     public override void _PhysicsProcess(float delta) => _sceneTree.Iteration(delta);
     public override void _ExitTree() => _sceneTree.Finish();
-
-    public void Start(ushort port) => Server.Start(port);
-    public void Stop() => Server.Stop();
 }

src/Network/NetworkSync.cs

@@ -101,6 +101,19 @@ public static class NetworkSync
         NetworkPackets.Send(server, new []{ networkID }, packet);
     }
 
+    internal static void ClearAllObjects()
+    {
+        foreach (var (node, _) in _statusByObject) {
+            if (!Godot.Object.IsInstanceValid(node)) continue;
+            node.GetParent().RemoveChild(node);
+            node.QueueFree();
+        }
+
+        _statusByObject.Clear();
+        _statusBySyncID.Clear();
+        _dirtyObjects.Clear();
+        _syncIDCounter = 1;
+    }
 
     public static uint GetSyncID(this Node obj)
         => GetSyncStatus(obj).SyncID;

src/Objects/Player.cs

@@ -12,7 +12,7 @@ public class Player : KinematicBody2D, IInitializer
     public Sprite Sprite { get; private set; }
 
 
-    public bool IsLocal { get; private set; }
+    public bool IsLocal { get; private set; } = false;
 
     [SyncProperty]
     public new Vector2 Position {
@@ -61,7 +61,7 @@ public class Player : KinematicBody2D, IInitializer
         if ((Position.y > 9000) && (this.GetGame() is Server server))
             this.RPC(new []{ server.GetNetworkID(this) }, ResetPosition, Vector2.Zero);
 
-        this.GetClient()?.RPC(Move, Position);
+        if (IsLocal) this.GetClient()?.RPC(Move, Position);
     }
 
     public override void _PhysicsProcess(float delta)

src/Scenes/Client.cs

@@ -1,14 +1,18 @@
 using System;
 using System.Collections.Generic;
 using Godot;
+using static Godot.NetworkedMultiplayerPeer;
 
 public class Client : Game
 {
     [Export] public NodePath CursorPath { get; set; }
     public Cursor Cursor { get; private set; }
 
-    public event Action OnConnected;
-    public event Action OnDisconnected;
+    public ConnectionStatus Status => CustomMultiplayer.NetworkPeer?.GetConnectionStatus() ?? ConnectionStatus.Disconnected;
+
+    public event Action Connected;
+    public event Action Disconnected;
+    public event Action<ConnectionStatus> StatusChanged;
 
     public Client()
     {
@@ -36,10 +40,13 @@ public class Client : Game
     {
         if (CustomMultiplayer.NetworkPeer != null)
             throw new InvalidOperationException("Client connection is already open");
-        var peer = new NetworkedMultiplayerENet();
+
+        var peer  = new NetworkedMultiplayerENet();
         var error = peer.CreateClient(address, port);
         if (error != Error.Ok) throw new Exception($"Error when connecting: {error}");
         CustomMultiplayer.NetworkPeer = peer;
+
+        StatusChanged?.Invoke(Status);
     }
 
     public void Disconnect()
@@ -47,12 +54,17 @@ public class Client : Game
         if (CustomMultiplayer.NetworkPeer == null) return;
         ((NetworkedMultiplayerENet)CustomMultiplayer.NetworkPeer).CloseConnection();
         CustomMultiplayer.NetworkPeer = null;
-        OnDisconnected?.Invoke();
+
+        Disconnected?.Invoke();
+        StatusChanged?.Invoke(Status);
     }
 
 
     private void OnConnectedToServer()
-        => OnConnected?.Invoke();
+    {
+        Connected?.Invoke();
+        StatusChanged?.Invoke(Status);
+    }
 
     private void OnPacketReceived(int id, byte[] bytes)
     {

src/Scenes/Server.cs

@@ -8,6 +8,13 @@ public class Server : Game
     private readonly Dictionary<NetworkID, Player> _playersByNetworkID = new Dictionary<NetworkID, Player>();
     private readonly Dictionary<Player, NetworkID> _networkIDByPlayer = new Dictionary<Player, NetworkID>();
 
+    private Player _localPlayer = null;
+    private bool _isLocalPlayerConnected = false;
+
+    public NetworkedMultiplayerENet Peer => (NetworkedMultiplayerENet)CustomMultiplayer.NetworkPeer;
+    public bool IsRunning => Peer != null;
+    public bool IsSingleplayer { get; private set; }
+
     public Server()
     {
         CustomMultiplayer = new MultiplayerAPI { RootNode = this };
@@ -24,30 +31,48 @@ public class Server : Game
     }
 
 
+    public ushort StartSingleplayer()
+    {
+        for (var retries = 0; ; retries++) {
+            try {
+                IsSingleplayer = true;
+                // TODO: When `get_local_port` is available, just use port 0 for an auto-assigned port.
+                //       Also see this PR: https://github.com/godotengine/godot/pull/48235
+                var port = (ushort)GD.RandRange(42000, 43000);
+                Start(port, "127.0.0.1", 1);
+                return port;
+            } catch (Exception ex) {
+                // Do throw the "Server is already running" exception.
+                // 3 retries should be well enough to find a random unused port.
+                if ((ex is InvalidOperationException) || (retries == 2)) throw;
+            }
+        }
+    }
     public void Start(ushort port)
+        => Start(port, "*", 32);
+    private void Start(ushort port, string bindIP, int maxClients)
     {
-        if (CustomMultiplayer.NetworkPeer != null)
-            throw new InvalidOperationException("Server is already running");
-        var peer  = new NetworkedMultiplayerENet();
-        var error = peer.CreateServer(port);
+        if (IsRunning) throw new InvalidOperationException("Server is already running");
+
+        var peer = new NetworkedMultiplayerENet();
+        peer.SetBindIp(bindIP);
+        peer.ServerRelay = false;
+
+        var error = peer.CreateServer(port, maxClients);
         if (error != Error.Ok) throw new Exception($"Error when starting the server: {error}");
-        CustomMultiplayer.NetworkPeer = peer;
 
-        // Spawn default blocks.
-        for (var x = -6; x <= 6; x++) {
-            var block = this.Spawn<Block>();
-            block.Position    = new BlockPos(x, 3);
-            block.Color       = Color.FromHsv(GD.Randf(), 0.1F, 1.0F);
-            block.Unbreakable = true;
-        }
+        CustomMultiplayer.NetworkPeer = peer;
     }
 
     public void Stop()
     {
-        if (CustomMultiplayer.NetworkPeer != null)
-            throw new InvalidOperationException("Server is not running");
-        ((NetworkedMultiplayerENet)CustomMultiplayer.NetworkPeer).CloseConnection();
+        if (!IsRunning) throw new InvalidOperationException("Server is not running");
+
+        Peer.CloseConnection();
         CustomMultiplayer.NetworkPeer = null;
+
+        IsSingleplayer = false;
+        _isLocalPlayerConnected = false;
     }
 
 
@@ -60,15 +85,34 @@ public class Server : Game
     private void OnPeerConnected(int id)
     {
         var networkID = new NetworkID(id);
-        NetworkSync.SendAllObjects(this, networkID);
 
-        var player = this.Spawn<Player>();
-        player.Position = Vector2.Zero;
-        player.Color    = Colors.Red;
+        if (IsSingleplayer) {
+            if (Peer.GetPeerAddress(id) != "127.0.0.1")
+                { Peer.DisconnectPeer(id, true); return; }
+            CustomMultiplayer.RefuseNewNetworkConnections = true;
+        }
 
-        _playersByNetworkID.Add(networkID, player);
-        _networkIDByPlayer.Add(player, networkID);
+        Player player;
+        if ((_localPlayer != null) && !_isLocalPlayerConnected &&
+            (Peer.GetPeerAddress(id) == "127.0.0.1")) {
+            player = _localPlayer;
+            _isLocalPlayerConnected = true;
+
+            var oldNetworkID = GetNetworkID(player);
+            _playersByNetworkID.Remove(oldNetworkID);
+            _playersByNetworkID.Add(networkID, player);
+            _networkIDByPlayer[player] = networkID;
+        } else {
+            NetworkSync.SendAllObjects(this, networkID);
+            player = this.Spawn<Player>();
+            player.Position = Vector2.Zero;
+            player.Color    = Colors.Red;
+
+            _playersByNetworkID.Add(networkID, player);
+            _networkIDByPlayer.Add(player, networkID);
+        }
 
+        if (IsSingleplayer) _localPlayer = player;
         player.RPC(new []{ networkID }, player.SetLocal);
     }
 
@@ -76,6 +120,10 @@ public class Server : Game
     {
         var networkID = new NetworkID(id);
         var player    = GetPlayer(networkID);
+
+        // Local player stays around for reconnecting.
+        if (_localPlayer == player) return;
+
         player.Destroy();
         _playersByNetworkID.Remove(networkID);
         _networkIDByPlayer.Remove(player);

src/Utility/Extensions.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using Godot;
 
 public static class Extensions
@@ -16,6 +17,10 @@ public static class Extensions
         (instance as IInitializer)?.Initialize();
         return instance;
     }
+
+    public static void Deconstruct<TKey, TValue>(
+            this KeyValuePair<TKey, TValue> kvp, out TKey key, out TValue value)
+        { key = kvp.Key; value = kvp.Value; }
 }
 
 public interface IInitializer