don't error when stopping

Pilz.Net/Api/ApiServer.cs

@@ -17,6 +17,7 @@ public class ApiServer(string apiUrl) : IApiServer
     protected int restartAttempts = 0;
     protected DateTime lastRestartAttempt;
     protected SemaphoreSlim? semaphore;
+    protected bool doListen;
 
     public event OnCheckAuthenticationEventHandler? OnCheckAuthentication;
     public event OnCheckContextEventHandler? OnCheckContext;
@@ -52,6 +53,7 @@ public class ApiServer(string apiUrl) : IApiServer
     {
         Log.Info("Starting listener");
         httpListener.Prefixes.Add(ApiUrl + "/");
+        doListen = true;
         httpListener.Start();
         Log.Info("Started listener");
         Receive();
@@ -60,6 +62,7 @@ public class ApiServer(string apiUrl) : IApiServer
     public virtual void Stop()
     {
         Log.Info("Stopping listener");
+        doListen = false;
         httpListener.Stop();
         Thread.Sleep(StopDelay);
         httpListener.Close();
@@ -181,7 +184,7 @@ public class ApiServer(string apiUrl) : IApiServer
         HttpListenerContext? context;
 
         // Skip if not lisstening anymore
-        if (!httpListener.IsListening)
+        if (!httpListener.IsListening || !doListen)
             return;
 
         // Wait for a free slot