Fix concurrent access issues with ConnectedClients

Replaced direct access to GameMain.Server.ConnectedClients with array snapshots in multiple server-side classes to prevent concurrent modification issues during parallel updates. Also updated PhysicsBody and LevelTrigger to avoid static/shared state in parallel contexts, improving thread safety and reliability.

Barotrauma/BarotraumaServer/ServerSource/Characters/Character.cs

@@ -28,11 +28,14 @@ namespace Barotrauma
                 }
             }
 
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+
             if (GameMain.Server is { ServerSettings.RespawnMode: RespawnMode.Permadeath } && 
                 GameMain.GameSession?.Campaign is MultiPlayerCampaign mpCampaign &&
                 causeOfDeath != CauseOfDeathType.Disconnected)
             {
-                Client ownerClient = GameMain.Server.ConnectedClients.FirstOrDefault(c => c.Character == this);
+                Client ownerClient = clients.FirstOrDefault(c => c.Character == this);
                 if (ownerClient != null)
                 {
                     ownerClient.SpectateOnly = true;
@@ -51,7 +54,7 @@ namespace Barotrauma
 
             if (HasAbilityFlag(AbilityFlags.RetainExperienceForNewCharacter))
             {
-                var ownerClient = GameMain.Server.ConnectedClients.Find(c => c.Character == this);
+                var ownerClient = clients.FirstOrDefault(c => c.Character == this);
                 if (ownerClient != null)
                 {
                     (GameMain.GameSession?.GameMode as MultiPlayerCampaign)?.SaveExperiencePoints(ownerClient);
@@ -62,7 +65,7 @@ namespace Barotrauma
 
             if (CauseOfDeath.Killer != null && CauseOfDeath.Killer.IsTraitor && CauseOfDeath.Killer != this)
             {
-                var owner = GameMain.Server.ConnectedClients.Find(c => c.Character == this);
+                var owner = clients.FirstOrDefault(c => c.Character == this);
                 if (owner != null)
                 {
                     if (!GameMain.LuaCs.Game.overrideTraitors)
@@ -71,7 +74,7 @@ namespace Barotrauma
                     }
                 }
             }
-            foreach (Client client in GameMain.Server.ConnectedClients)
+            foreach (Client client in clients)
             {
                 if (client.InGame)
                 {

Barotrauma/BarotraumaServer/ServerSource/Characters/CharacterNetworking.cs

@@ -490,7 +490,9 @@ namespace Barotrauma
                 case ControlEventData controlEventData:
                     Client owner = controlEventData.Owner;
                     msg.WriteBoolean(owner == c && owner.Character == this);
-                    msg.WriteByte(owner != null && owner.Character == this && GameMain.Server.ConnectedClients.Contains(owner) ? owner.SessionId : (byte)0);
+                    // Create snapshot to avoid concurrent access issues during parallel updates
+                    var connectedClients = GameMain.Server.ConnectedClients.ToArray();
+                    msg.WriteByte(owner != null && owner.Character == this && connectedClients.Contains(owner) ? owner.SessionId : (byte)0);
                     msg.WriteBoolean(info is { RenamingEnabled: true });
                     break;
                 case CharacterStatusEventData statusEventData:
@@ -746,7 +748,9 @@ namespace Barotrauma
                 return;
             }
 
-            Client ownerClient = GameMain.Server.ConnectedClients.Find(c => c.Character == this && (!c.SpectateOnly || !GameMain.Server.ServerSettings.AllowSpectating));
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            Client ownerClient = clients.FirstOrDefault(c => c.Character == this && (!c.SpectateOnly || !GameMain.Server.ServerSettings.AllowSpectating));
             if (ownerClient != null)
             {
                 msg.WriteBoolean(true);

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/ConversationAction.cs

@@ -82,10 +82,13 @@ namespace Barotrauma
 
         private bool IsBlockedByAnotherConversation(IEnumerable<Entity> targets, float duration)
         {
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            
             if (targets == null || targets.None())
             {
                 //if the action doesn't target anyone in specific, it's shown to every client
-                foreach (var client in GameMain.Server.ConnectedClients)
+                foreach (var client in clients)
                 {
                     if (IsBlockedByAnotherConversation(client, duration)) { return true; }
                 }
@@ -95,7 +98,7 @@ namespace Barotrauma
                 foreach (Entity e in targets)
                 {
                     if (e is not Character character || !character.IsRemotePlayer) { continue; }
-                    Client targetClient = GameMain.Server.ConnectedClients.Find(c => c.Character == character);
+                    Client targetClient = clients.FirstOrDefault(c => c.Character == character);
                     if (targetClient != null && IsBlockedByAnotherConversation(targetClient, duration)) { return true; }                    
                 }
             }
@@ -117,13 +120,16 @@ namespace Barotrauma
         partial void ShowDialog(Character speaker, Character targetCharacter)
         {
             targetClients.Clear();
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            
             if (!TargetTag.IsEmpty)
             {
                 IEnumerable<Entity> entities = ParentEvent.GetTargets(TargetTag);
                 foreach (Entity e in entities)
                 {
                     if (e is not Character character || !character.IsRemotePlayer) { continue; }
-                    Client targetClient = GameMain.Server.ConnectedClients.Find(c => c.Character == character);
+                    Client targetClient = clients.FirstOrDefault(c => c.Character == character);
                     if (targetClient != null) 
                     {
                         targetClients.Add(targetClient);
@@ -135,7 +141,7 @@ namespace Barotrauma
             }
             else
             {
-                foreach (Client c in GameMain.Server.ConnectedClients)
+                foreach (Client c in clients)
                 {
                     if (CanClientReceive(c))
                     {

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/EventLogAction.cs

@@ -9,48 +9,52 @@ namespace Barotrauma;
 
 partial class EventLogAction : EventAction
 {
-    partial void AddEntryProjSpecific(EventLog? eventLog, string displayText)
+partial void AddEntryProjSpecific(EventLog? eventLog, string displayText)
+{
+    if (eventLog == null) { return; }
+    
+    // Create snapshot to avoid concurrent access issues during parallel updates
+    var clients = GameMain.Server.ConnectedClients.ToArray();
+    
+    if (!TargetTag.IsEmpty)
     {
-        if (eventLog == null) { return; }
+        List<Client> targetClients = new List<Client>();
-        if (!TargetTag.IsEmpty)
+        foreach (var target in ParentEvent.GetTargets(TargetTag))
         {
-            List<Client> targetClients = new List<Client>();
+            if (target is Character character)
-            foreach (var target in ParentEvent.GetTargets(TargetTag))
             {
-                if (target is Character character)
+                var ownerClient = clients.FirstOrDefault(c => c.Character == character);
+                if (ownerClient != null)
                 {
-                    var ownerClient = GameMain.Server.ConnectedClients.Find(c => c.Character == character);
+                    targetClients.Add(ownerClient);
-                    if (ownerClient != null)
-                    {
-                        targetClients.Add(ownerClient);
-                    }
-                }
-                else
-                {
-                    DebugConsole.AddWarning($"{target} is not a valid target for an EventLogAction. The target should be a character.",
-                        ParentEvent.Prefab.ContentPackage);
                 }
             }
-            if (eventLog!.TryAddEntry(ParentEvent.Prefab.Identifier, Id, displayText, targetClients) && ShowInServerLog)
+            else
             {
-                Log(targetClients);
+                DebugConsole.AddWarning($"{target} is not a valid target for an EventLogAction. The target should be a character.",
+                    ParentEvent.Prefab.ContentPackage);
             }
         }
-        else
+        if (eventLog!.TryAddEntry(ParentEvent.Prefab.Identifier, Id, displayText, targetClients) && ShowInServerLog)
         {
-            if (eventLog.TryAddEntry(ParentEvent.Prefab.Identifier, Id, displayText, GameMain.Server.ConnectedClients) && ShowInServerLog)
+            Log(targetClients);
-            {
-                Log(targetClients: null);
-            }
-        }
-
-        void Log(List<Client>? targetClients)
-        {
-            string clientStr = targetClients == null || targetClients.None() ?
-                string.Empty :
-                $" ({string.Join(", ", targetClients.Select(c => NetworkMember.ClientLogName(c)))})";
-            GameServer.Log($"Event \"{ParentEvent.Prefab.Name}\"{clientStr}: " + displayText,
-                ParentEvent is TraitorEvent ? ServerLog.MessageType.Traitors : ServerLog.MessageType.Chat);
         }
     }
+    else
+    {
+        if (eventLog.TryAddEntry(ParentEvent.Prefab.Identifier, Id, displayText, clients) && ShowInServerLog)
+        {
+            Log(targetClients: null);
+        }
+    }
+
+    void Log(List<Client>? targetClients)
+    {
+        string clientStr = targetClients == null || targetClients.None() ?
+            string.Empty :
+            $" ({string.Join(", ", targetClients.Select(c => NetworkMember.ClientLogName(c)))})";
+        GameServer.Log($"Event \"{ParentEvent.Prefab.Name}\"{clientStr}: " + displayText,
+            ParentEvent is TraitorEvent ? ServerLog.MessageType.Traitors : ServerLog.MessageType.Chat);
+    }
+}
 }

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/EventObjectiveAction.cs

@@ -1,3 +1,5 @@
+using System.Linq;
+
 namespace Barotrauma
 {
     partial class EventObjectiveAction : EventAction
@@ -13,9 +15,12 @@ namespace Barotrauma
                 ParentObjectiveId,
                 CanBeCompleted);
 
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+
             if (TargetTag.IsEmpty)
             {
-                foreach (var client in GameMain.Server.ConnectedClients)
+                foreach (var client in clients)
                 {
                     if (client.Character == null) { continue; }
                     EventManager.ServerWriteObjective(client, objective);
@@ -26,11 +31,11 @@ namespace Barotrauma
                 foreach (var target in ParentEvent.GetTargets(TargetTag))
                 {
                     if (target is not Character character) { continue; }
-                    var ownerClient = GameMain.Server.ConnectedClients.Find(c => c.Character == character);
+                    var ownerClient = clients.FirstOrDefault(c => c.Character == character);
                     if (ownerClient == null) { continue; }
                     EventManager.ServerWriteObjective(ownerClient, objective);
                 }
             }
         }
     }
-}
+}

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/HighlightAction.cs

@@ -14,8 +14,10 @@ partial class HighlightAction : EventAction
             IEnumerable<Client>? targetClients = null;
             if (targetCharacters != null)
             {
+                // Create snapshot to avoid concurrent access issues during parallel updates
+                var clients = GameMain.Server.ConnectedClients.ToArray();
                 targetClients = targetCharacters
-                    .Select(c => GameMain.Server.ConnectedClients.FirstOrDefault(client => client.Character == c))
+                    .Select(c => clients.FirstOrDefault(client => client.Character == c))
                     .Where(c => c != null)!;
             }
             GameMain.Server?.CreateEntityEvent(item, new Item.SetHighlightEventData(State, highlightColor, targetClients));

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/MissionAction.cs

@@ -1,5 +1,6 @@
-using Barotrauma.Networking;
+using Barotrauma.Networking;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Barotrauma
 {
@@ -22,7 +23,9 @@ namespace Barotrauma
 
         private static void NotifyMissionUnlock(Mission mission)
         {
-            foreach (Client client in GameMain.Server.ConnectedClients)
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            foreach (Client client in clients)
             {
                 NotifyMissionUnlock(mission, client);
             }
@@ -40,4 +43,4 @@ namespace Barotrauma
             GameMain.Server.ServerPeer.Send(outmsg, client.Connection, DeliveryMethod.Reliable);            
         }
     }
-}
+}

Barotrauma/BarotraumaServer/ServerSource/Events/EventActions/StatusEffectAction.cs

@@ -25,4 +25,4 @@ namespace Barotrauma
             }
         }
     }
-}
+}

Barotrauma/BarotraumaServer/ServerSource/Items/Components/Signal/CircuitBox.cs

@@ -76,7 +76,9 @@ namespace Barotrauma.Items.Components
         {
             var (msg, deliveryMethod) = PrepareToSend(opcode, data);
 
-            foreach (Client client in GameMain.Server.ConnectedClients)
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            foreach (Client client in clients)
             {
                 if (predicate is not null && !predicate(client)) { continue; }
 
@@ -391,4 +393,4 @@ namespace Barotrauma.Items.Components
             CreateServerEvent(new CircuitBoxServerUpdateSelection(nodes, wires, ios, labels));
         }
     }
-}
+}

Barotrauma/BarotraumaServer/ServerSource/Map/Hull.cs

@@ -29,7 +29,9 @@ namespace Barotrauma
 
             //don't create updates if all clients are very far from the hull
             float hullUpdateDistanceSqr = NetConfig.HullUpdateDistance * NetConfig.HullUpdateDistance;
-            if (!GameMain.Server.ConnectedClients.Any(c => 
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            if (!clients.Any(c => 
                     (c.Character != null && Vector2.DistanceSquared(c.Character.WorldPosition, WorldPosition) < hullUpdateDistanceSqr) ||
                     (c.SpectatePos != null && Vector2.DistanceSquared(c.SpectatePos.Value, WorldPosition) < hullUpdateDistanceSqr)) )
             {

Barotrauma/BarotraumaServer/ServerSource/Networking/GameServer.cs

@@ -4799,7 +4799,9 @@ namespace Barotrauma.Networking
         public static string CharacterLogName(Character character)
         {
             if (character == null) { return "[NULL]"; }
-            Client client = GameMain.Server.ConnectedClients.Find(c => c.Character == character);
+            // Create snapshot to avoid concurrent access issues during parallel updates
+            var clients = GameMain.Server.ConnectedClients.ToArray();
+            Client client = clients.FirstOrDefault(c => c.Character == character);
             return ClientLogName(client, character.LogName);
         }
 
@@ -4810,8 +4812,8 @@ namespace Barotrauma.Networking
             GameMain.LuaCs?.Hook?.Call("serverLog", line, messageType);
 
             GameMain.Server.ServerSettings.ServerLog.WriteLine(line, messageType);
-
+            var clients = GameMain.Server.ConnectedClients.ToArray();
-            foreach (Client client in GameMain.Server.ConnectedClients)
+            foreach (Client client in clients)
             {
                 if (!client.HasPermission(ClientPermissions.ServerLog)) continue;
                 //use sendername as the message type

Barotrauma/BarotraumaShared/SharedSource/Map/Levels/LevelObjects/LevelTrigger.cs

@@ -673,13 +673,17 @@ namespace Barotrauma
             }
         }
 
-        private static readonly List<Entity> triggerersToRemove = new List<Entity>();
         public static void RemoveInActiveTriggerers(PhysicsBody physicsBody, HashSet<Entity> triggerers)
         {
             if (physicsBody == null) { return; }
 
-            triggerersToRemove.Clear();
+            // Use local list instead of static field to avoid concurrent access issues during parallel updates
-            foreach (var triggerer in triggerers)
+            var triggerersToRemove = new List<Entity>();
+            
+            // Create snapshot to avoid concurrent modification during enumeration
+            var triggererSnapshot = triggerers.ToArray();
+            
+            foreach (var triggerer in triggererSnapshot)
             {
                 if (triggerer.Removed)
                 {

Barotrauma/BarotraumaShared/SharedSource/Physics/PhysicsBody.cs

@@ -834,6 +834,12 @@ namespace Barotrauma
             if (!IsValidValue(simPosition, "position", -1e10f, 1e10f)) { return false; }
             if (!IsValidValue(rotation, "rotation")) { return false; }
 
+            if (PhysicsBodyQueue.IsInParallelContext)
+            {
+                PhysicsBodyQueue.Enqueue(() => SetTransform(simPosition, rotation, setPrevTransform));
+                return true;
+            }
+
             FarseerBody.SetTransform(simPosition, rotation);
             if (setPrevTransform) { SetPrevTransform(simPosition, rotation); }
             return true;
@@ -848,6 +854,12 @@ namespace Barotrauma
             if (!IsValidValue(simPosition, "position", -1e10f, 1e10f)) { return false; }
             if (!IsValidValue(rotation, "rotation")) { return false; }
 
+            if (PhysicsBodyQueue.IsInParallelContext)
+            {
+                PhysicsBodyQueue.Enqueue(() => SetTransformIgnoreContacts(simPosition, rotation, setPrevTransform));
+                return true;
+            }
+
             FarseerBody.SetTransformIgnoreContacts(ref simPosition, rotation);
             if (setPrevTransform) { SetPrevTransform(simPosition, rotation); }
             return true;