Fixes from code review

Author: josesimoes

README.md

@@ -63,7 +63,7 @@ NetworkHelper.SetupNetworkHelper(requiresDateTime: true);
 
 `SetupNetworkHelper` throws `InvalidOperationException` if called a second time without a prior `Reset()`. Token-based methods (`SetupAndConnectNetwork`) do not have this restriction and are always retryable.
 
-## 
+## Feedback and documentation
 
 For documentation, providing feedback, issues and finding out how to contribute please refer to the [Home repo](https://github.com/nanoframework/Home).
 

Tests/NetworkHelperTests/ConnectToEthernetTests.cs

@@ -107,7 +107,11 @@ public void TestRetryAfterTimeout()
 
             // If there is a network, second attempt should succeed;
             // if not, it will time out again — either way, it must NOT throw
-            Assert.IsTrue(NetworkHelper.Status != NetworkHelperStatus.None);
+            Assert.IsTrue(
+                NetworkHelper.Status == NetworkHelperStatus.NetworkIsReady ||
+                NetworkHelper.Status == NetworkHelperStatus.TokenExpiredWaitingIPAddress ||
+                NetworkHelper.Status == NetworkHelperStatus.TokenExpiredWaitingDateTime,
+                "Expected a terminal status after the second attempt");
 
             NetworkHelper.Reset();
         }

nanoFramework.System.Net/NetworkHelper/NetworkHelper.cs

@@ -27,6 +27,9 @@ public static class NetworkHelper
 
         private static IPConfiguration _ipConfiguration;
 
+        private static Thread _workerThread;
+        private static volatile bool _stopRequested;
+
         /// <summary>
         /// This flag will make sure there is only one and only one call to the event-based helper methods.
         /// </summary>
@@ -69,7 +72,8 @@ public static void SetupNetworkHelper(bool requiresDateTime = false)
             SetupHelper(true);
 
             // fire working thread
-            new Thread(WorkingThread).Start();
+            _workerThread = new Thread(WorkingThread);
+            _workerThread.Start();
         }
 
         /// <summary>
@@ -90,7 +94,8 @@ public static void SetupNetworkHelper(
             SetupHelper(true);
 
             // fire working thread
-            new Thread(WorkingThread).Start();
+            _workerThread = new Thread(WorkingThread);
+            _workerThread.Start();
         }
 
         /// <summary>
@@ -143,6 +148,22 @@ public static void Reset()
             // deregister event handler to prevent a handler leak
             NetworkChange.NetworkAddressChanged -= AddressChangedCallback;
 
+            // signal the worker thread to stop and unblock it if it is waiting for an IP address
+            _stopRequested = true;
+
+            if (_ipAddressAvailable != null)
+            {
+                _ipAddressAvailable.Set();
+            }
+
+            if (_workerThread != null)
+            {
+                // give the thread a moment to exit cleanly before clearing shared state
+                _workerThread.Join(1000);
+                _workerThread = null;
+            }
+
+            _stopRequested = false;
             _helperInstanciated = false;
             _ipAddressAvailable = null;
             _networkReady = new(false);
@@ -228,16 +249,28 @@ private static void WorkingThread()
                 _workingNetworkInterface,
                 _ipConfiguration))
             {
-                // wait here until we have an IP address
+                // wait here until we have an IP address or until Reset() unblocks us
                 _ipAddressAvailable.WaitOne();
             }
 
+            // bail out if Reset() was called while we were waiting
+            if (_stopRequested)
+            {
+                return;
+            }
+
             if (_requiresDateTime)
             {
                 // wait until there is a valid DateTime
                 NetworkHelperInternal.WaitForValidDateTime();
             }
 
+            // bail out if Reset() was called during the DateTime wait
+            if (_stopRequested)
+            {
+                return;
+            }
+
             // all conditions met
             _networkReady.Set();
 
@@ -247,6 +280,11 @@ private static void WorkingThread()
 
         private static void AddressChangedCallback(object sender, EventArgs e)
         {
+            if (_stopRequested)
+            {
+                return;
+            }
+
             if (NetworkHelperInternal.CheckIP(
                 _workingNetworkInterface,
                 _ipConfiguration))

nanoFramework.System.Net/NetworkHelper/NetworkHelperStatus.cs

@@ -43,13 +43,13 @@ public enum NetworkHelperStatus
         ErrorConnetingToWiFiWhileScanning,
 
         /// <summary>
-        /// The network was previously ready but the IP address was lost. Waiting for the connection to be restored.
+        /// An exception occurred with waiting for the network to become ready. Check HelperException property to find the <see cref="Exception"/> that was thrown.
         /// </summary>
-        Reconnecting,
+        ExceptionOccurred,
 
         /// <summary>
-        /// An exception occurred with waiting for the network to become ready. Check HelperException property to find the <see cref="Exception"/> that was thrown.
+        /// The network was previously ready but the IP address was lost. Waiting for the connection to be restored.
         /// </summary>
-        ExceptionOccurred
+        Reconnecting
     }
 }