dotnet - add locking since the simulator seems to run a lot in parallel

change the port to match what the simulator uses by default

add serilog as part of debugging

dotnet/SafelyYou/Devices.cs

@@ -16,6 +16,7 @@ public sealed class KnownDevices
 
 public sealed class DeviceHeartBeatHistory
 {
+    private readonly Lock _lock = new();
 
     public enum AddResult { Added, OutOfSequence }
 
@@ -26,36 +27,43 @@ public sealed class DeviceHeartBeatHistory
 
     public AddResult Add(DateTimeOffset sentAt)
     {
-        // Reject heartbeats that arrive before the latest registered time.
-        // Gaps are fine: uptime can be derived from first, last, and count.
-        if (LastHeartBeat is null)
+        lock (_lock)
         {
-            FirstHeartBeat = sentAt;
+            // Reject heartbeats that arrive before the latest registered time.
+            // Gaps are fine: uptime can be derived from first, last, and count.
+            if (LastHeartBeat is null)
+            {
+                FirstHeartBeat = sentAt;
+                LastHeartBeat = sentAt;
+                NumberOfHeartBeats = 1;
+                return AddResult.Added;
+            }
+
+            if (sentAt < LastHeartBeat)
+                return AddResult.OutOfSequence;
+
+            // note: does not account for rejecting heartbeats that come between the one minute window.
             LastHeartBeat = sentAt;
-            NumberOfHeartBeats = 1;
+            NumberOfHeartBeats++;
             return AddResult.Added;
         }
-
-        if (sentAt < LastHeartBeat)
-            return AddResult.OutOfSequence;
-
-        // note: does not account for rejecting heartbeats that come between the one minute window.
-        LastHeartBeat = sentAt;
-        NumberOfHeartBeats++;
-        return AddResult.Added;
     }
 }
 
 public sealed class HeartBeatHistories
 {
     private readonly ConcurrentDictionary<DeviceId, DeviceHeartBeatHistory> _histories = new();
+    private readonly Lock _lock = new ();
 
     public DeviceHeartBeatHistory.AddResult Add(DeviceId deviceId, DateTimeOffset sentAt)
     {
         if (!_histories.TryGetValue(deviceId, out var history))
         {
-            history = new();
-            _histories[deviceId] = history;
+            lock (_lock)
+            {
+                history = new();
+                _histories[deviceId] = history;
+            }
         }
 
         return history.Add(sentAt);