diff --git a/Nefarius.Peripherals.SerialPort/SerialPort.cs b/Nefarius.Peripherals.SerialPort/SerialPort.cs
index 1836c73..6c549ea 100644
--- a/Nefarius.Peripherals.SerialPort/SerialPort.cs
+++ b/Nefarius.Peripherals.SerialPort/SerialPort.cs
@@ -22,6 +22,7 @@ public partial class SerialPort : IDisposable
     private readonly ManualResetEvent _writeEvent = new(false);
     private bool _auto;
     private bool _checkSends = true;
+    private CancellationTokenSource _cts;
 
     private Handshake _handShake;
     private SafeFileHandle _hPort;
@@ -30,7 +31,6 @@ public partial class SerialPort : IDisposable
     private Exception _rxException;
     private bool _rxExceptionReported;
     private Thread _rxThread;
-    private CancellationTokenSource _cts;
     private int _stateBrk = 2;
     private int _stateDtr = 2;
     private int _stateRts = 2;
@@ -177,22 +177,24 @@ public partial class SerialPort : IDisposable
     /// </summary>
     public void Close()
     {
-        if (_online)
+        if (!_online)
         {
-            _auto = false;
-            BeforeClose(false);
-            InternalClose();
-            _rxException = null;
+            return;
         }
+
+        _auto = false;
+        BeforeClose(false);
+        InternalClose();
+        _rxException = null;
     }
 
     private void InternalClose()
     {
-        _cts.Cancel();
         PInvoke.CancelIo(_hPort);
 
         if (_rxThread != null)
         {
+            _cts.Cancel();
             _rxThread.Join();
             _rxThread = null;
         }
@@ -407,6 +409,9 @@ public partial class SerialPort : IDisposable
     {
     }
 
+    /// <summary>
+    ///     Invoked when a single character has been received.
+    /// </summary>
     public event Action<byte> DataReceived;
 
     /// <summary>
@@ -482,7 +487,7 @@ public partial class SerialPort : IDisposable
                 {
                     if (Marshal.GetLastWin32Error() == (int)WIN32_ERROR.ERROR_IO_PENDING)
                     {
-                        sg.WaitOne();
+                        WaitHandle.WaitAny(new[] { sg, _cts.Token.WaitHandle });
                     }
                     else
                     {
diff --git a/PInvokeSerialPort.Sample/Program.cs b/PInvokeSerialPort.Sample/Program.cs
index 8ebda6f..8668ba6 100755
--- a/PInvokeSerialPort.Sample/Program.cs
+++ b/PInvokeSerialPort.Sample/Program.cs
@@ -20,5 +20,7 @@ internal class Program
         serialPort.Write("START\r\n");
 
         Console.ReadKey();
+
+        serialPort.Close();
     }
 }
\ No newline at end of file