Feature: Allow simulating outbound networking

LiteNetLib/LiteNetLib.csproj

@@ -26,6 +26,10 @@
     <DefineConstants>TRACE</DefineConstants>
   </PropertyGroup>
 
+  <PropertyGroup Condition="'$(SimulateNetwork)'=='true'">
+    <DefineConstants>$(DefineConstants);SIMULATE_NETWORK</DefineConstants>
+  </PropertyGroup>
+
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DefineConstants>$(DefineConstants);LITENETLIB_UNSAFE</DefineConstants>

LiteNetLib/NetManager.Socket.cs

@@ -532,6 +532,44 @@ internal int SendRaw(byte[] message, int start, int length, IPEndPoint remoteEnd
                 message = expandedPacket.RawData;
             }
 
+#if DEBUG || SIMULATE_NETWORK
+            if (HandleSimulateOutboundPacketLoss())
+            {
+                if (expandedPacket != null)
+                    PoolRecycle(expandedPacket);
+                return 0; // Simulate successful send to avoid triggering error handling
+            }
+
+            if (HandleSimulateOutboundLatency(message, start, length, remoteEndPoint))
+            {
+                if (expandedPacket != null)
+                    PoolRecycle(expandedPacket);
+                return length; // Simulate successful send
+            }
+#endif
+
+            return SendRawCoreWithCleanup(message, start, length, remoteEndPoint, expandedPacket);
+        }
+
+        private int SendRawCoreWithCleanup(byte[] message, int start, int length, IPEndPoint remoteEndPoint, NetPacket expandedPacket)
+        {
+            try
+            {
+                return SendRawCore(message, start, length, remoteEndPoint);
+            }
+            finally
+            {
+                if (expandedPacket != null)
+                    PoolRecycle(expandedPacket);
+            }
+        }
+
+        // Core socket sending logic without simulation - used by both SendRaw and delayed packet processing
+        internal int SendRawCore(byte[] message, int start, int length, IPEndPoint remoteEndPoint)
+        {
+            if (!_isRunning)
+                return 0;
+
             var socket = _udpSocketv4;
             if (remoteEndPoint.AddressFamily == AddressFamily.InterNetworkV6 && IPv6Support)
             {
@@ -604,11 +642,6 @@ internal int SendRaw(byte[] message, int start, int length, IPEndPoint remoteEnd
                 NetDebug.WriteError($"[S] {ex}");
                 return 0;
             }
-            finally
-            {
-                if (expandedPacket != null)
-                    PoolRecycle(expandedPacket);
-            }
 
             if (result <= 0)
                 return 0;

LiteNetLib/NetManager.cs

@@ -130,6 +130,17 @@ private struct IncomingData
             public DateTime TimeWhenGet;
         }
         private readonly List<IncomingData> _pingSimulationList = new List<IncomingData>();
+
+        private struct OutboundDelayedPacket
+        {
+            public byte[] Data;
+            public int Start;
+            public int Length;
+            public IPEndPoint EndPoint;
+            public DateTime TimeWhenSend;
+        }
+        private readonly List<OutboundDelayedPacket> _outboundSimulationList = new List<OutboundDelayedPacket>();
+
         private readonly Random _randomGenerator = new Random();
         private const int MinLatencyThreshold = 5;
 
@@ -193,12 +204,12 @@ private struct IncomingData
         public int DisconnectTimeout = 5000;
 
         /// <summary>
-        /// Simulate packet loss by dropping random amount of packets. (Works only in DEBUG mode)
+        /// Simulate packet loss by dropping random amount of packets. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)
         /// </summary>
         public bool SimulatePacketLoss = false;
 
         /// <summary>
-        /// Simulate latency by holding packets for random time. (Works only in DEBUG mode)
+        /// Simulate latency by holding packets for random time. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)
         /// </summary>
         public bool SimulateLatency = false;
 
@@ -208,12 +219,12 @@ private struct IncomingData
         public int SimulationPacketLossChance = 10;
 
         /// <summary>
-        /// Minimum simulated latency (in milliseconds)
+        /// Minimum simulated round-trip latency (in milliseconds). Actual latency applied per direction is half of this value.
         /// </summary>
         public int SimulationMinLatency = 30;
 
         /// <summary>
-        /// Maximum simulated latency (in milliseconds)
+        /// Maximum simulated round-trip latency (in milliseconds). Actual latency applied per direction is half of this value.
         /// </summary>
         public int SimulationMaxLatency = 100;
 
@@ -614,7 +625,7 @@ private void UpdateLogic()
             stopwatch.Stop();
         }
 
-        [Conditional("DEBUG")]
+        [Conditional("DEBUG"), Conditional("SIMULATE_NETWORK")]
         private void ProcessDelayedPackets()
         {
             if (!SimulateLatency)
@@ -634,6 +645,21 @@ private void ProcessDelayedPackets()
                     }
                 }
             }
+
+            lock (_outboundSimulationList)
+            {
+                for (int i = 0; i < _outboundSimulationList.Count; i++)
+                {
+                    var outboundData = _outboundSimulationList[i];
+                    if (outboundData.TimeWhenSend <= time)
+                    {
+                        // Send the delayed packet directly to socket layer bypassing simulation
+                        SendRawCore(outboundData.Data, outboundData.Start, outboundData.Length, outboundData.EndPoint);
+                        _outboundSimulationList.RemoveAt(i);
+                        i--;
+                    }
+                }
+            }
         }
 
         private void ProcessNtpRequests(float elapsedMilliseconds)
@@ -816,32 +842,33 @@ private void OnMessageReceived(NetPacket packet, IPEndPoint remoteEndPoint)
             HandleMessageReceived(packet, remoteEndPoint);
         }
 
-        [Conditional("DEBUG")]
+        [Conditional("DEBUG"), Conditional("SIMULATE_NETWORK")]
         private void HandleSimulateLatency(NetPacket packet, IPEndPoint remoteEndPoint)
         {
             if (!SimulateLatency)
             {
                 return;
             }
 
-            int latency = _randomGenerator.Next(SimulationMinLatency, SimulationMaxLatency);
-            if (latency > MinLatencyThreshold)
+            int roundTripLatency = _randomGenerator.Next(SimulationMinLatency, SimulationMaxLatency);
+            int inboundLatency = roundTripLatency / 2;
+            if (inboundLatency > MinLatencyThreshold)
             {
                 lock (_pingSimulationList)
                 {
                     _pingSimulationList.Add(new IncomingData
                     {
                         Data = packet,
                         EndPoint = remoteEndPoint,
-                        TimeWhenGet = DateTime.UtcNow.AddMilliseconds(latency)
+                        TimeWhenGet = DateTime.UtcNow.AddMilliseconds(inboundLatency)
                     });
                 }
                 // hold packet
                 _dropPacket = true;
             }
         }
 
-        [Conditional("DEBUG")]
+        [Conditional("DEBUG"), Conditional("SIMULATE_NETWORK")]
         private void HandleSimulatePacketLoss()
         {
             if (SimulatePacketLoss && _randomGenerator.NextDouble() * 100 < SimulationPacketLossChance)
@@ -850,6 +877,48 @@ private void HandleSimulatePacketLoss()
             }
         }
 
+#if DEBUG || SIMULATE_NETWORK
+        private bool HandleSimulateOutboundLatency(byte[] data, int start, int length, IPEndPoint remoteEndPoint)
+        {
+            if (!SimulateLatency)
+            {
+                return false;
+            }
+
+            int roundTripLatency = _randomGenerator.Next(SimulationMinLatency, SimulationMaxLatency);
+            int outboundLatency = roundTripLatency / 2;
+            if (outboundLatency > MinLatencyThreshold)
+            {
+                // Create a copy of the data to avoid issues with recycled packets
+                byte[] dataCopy = new byte[length];
+                Array.Copy(data, start, dataCopy, 0, length);
+
+                lock (_outboundSimulationList)
+                {
+                    _outboundSimulationList.Add(new OutboundDelayedPacket
+                    {
+                        Data = dataCopy,
+                        Start = 0,
+                        Length = length,
+                        EndPoint = remoteEndPoint,
+                        TimeWhenSend = DateTime.UtcNow.AddMilliseconds(outboundLatency)
+                    });
+                }
+
+                return true;
+            }
+            return false;
+        }
+#endif
+
+#if DEBUG || SIMULATE_NETWORK
+        private bool HandleSimulateOutboundPacketLoss()
+        {
+            bool shouldDrop = SimulatePacketLoss && _randomGenerator.NextDouble() * 100 < SimulationPacketLossChance;
+            return shouldDrop;
+        }
+#endif
+
         private void HandleMessageReceived(NetPacket packet, IPEndPoint remoteEndPoint)
         {
             var originalPacketSize = packet.Size;
@@ -1637,19 +1706,27 @@ public void Stop(bool sendDisconnectMessages)
             _lastPeerId = 0;
 
             ClearPingSimulationList();
+            ClearOutboundSimulationList();
 
             _connectedPeersCount = 0;
             _pendingEventHead = null;
             _pendingEventTail = null;
         }
 
-        [Conditional("DEBUG")]
+        [Conditional("DEBUG"), Conditional("SIMULATE_NETWORK")]
         private void ClearPingSimulationList()
         {
             lock (_pingSimulationList)
                 _pingSimulationList.Clear();
         }
 
+        [Conditional("DEBUG"), Conditional("SIMULATE_NETWORK")]
+        private void ClearOutboundSimulationList()
+        {
+            lock (_outboundSimulationList)
+                _outboundSimulationList.Clear();
+        }
+
         /// <summary>
         /// Return peers count with connection state
         /// </summary>

docfx_project/index.md

@@ -113,10 +113,10 @@ server.Stop();
   * (including library internal keepalive packets)
   * default value: **5000 msec**.
 * **SimulatePacketLoss**
-  * simulate packet loss by dropping random amout of packets. (Works only in DEBUG mode)
+  * simulate packet loss by dropping random amout of packets. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)
   * default value: **false**
 * **SimulateLatency**
-  * simulate latency by holding packets for random time. (Works only in DEBUG mode)
+  * simulate latency by holding packets for random time. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)
   * default value: **false**
 * **SimulationPacketLossChance**
   * chance of packet loss when simulation enabled. value in percents.

docs/api/LiteNetLib.NetManager.html

@@ -586,7 +586,7 @@ <h5 class="fieldValue">Field Value</h5>
 
 
   <h4 id="LiteNetLib_NetManager_SimulateLatency" data-uid="LiteNetLib.NetManager.SimulateLatency">SimulateLatency</h4>
-  <div class="markdown level1 summary"><p>Simulate latency by holding packets for random time. (Works only in DEBUG mode)</p>
+  <div class="markdown level1 summary"><p>Simulate latency by holding packets for random time. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)</p>
 </div>
   <div class="markdown level1 conceptual"></div>
   <h5 class="declaration">Declaration</h5>
@@ -611,7 +611,7 @@ <h5 class="fieldValue">Field Value</h5>
 
 
   <h4 id="LiteNetLib_NetManager_SimulatePacketLoss" data-uid="LiteNetLib.NetManager.SimulatePacketLoss">SimulatePacketLoss</h4>
-  <div class="markdown level1 summary"><p>Simulate packet loss by dropping random amount of packets. (Works only in DEBUG mode)</p>
+  <div class="markdown level1 summary"><p>Simulate packet loss by dropping random amount of packets. (Works only in DEBUG builds or when SIMULATE_NETWORK is defined)</p>
 </div>
   <div class="markdown level1 conceptual"></div>
   <h5 class="declaration">Declaration</h5>