Improve serial read/receive operations

nanoFramework.Tools.DebugLibrary.Shared/WireProtocol/Controller.cs

@@ -14,6 +14,7 @@ public class Controller : IControllerLocal
     {
         private ushort lastOutboundMessage;
         private readonly Semaphore _sendSemaphore = new Semaphore(1, 1);
+        private readonly Semaphore _receiveSemaphore = new Semaphore(1, 1);
         private readonly int nextEndpointId;
         private readonly object incrementLock = new object();
 
@@ -46,7 +47,10 @@ private void ProcessExit()
 
         public async Task<bool> SendAsync(MessageRaw raw, CancellationToken cancellationToken)
         {
-            _sendSemaphore.WaitOne();
+            if(!_sendSemaphore.WaitOne())
+            {
+                return false;
+            }
 
             // check for cancellation request
             if (cancellationToken.IsCancellationRequested)
@@ -149,6 +153,11 @@ private async Task<uint> SendRawBufferAsync(byte[] buffer, TimeSpan waiTimeout,
 
         internal async Task<int> ReadBufferAsync(byte[] buffer, int offset, int bytesToRead, TimeSpan waitTimeout, CancellationToken cancellationToken)
         {
+            if (!_receiveSemaphore.WaitOne())
+            {
+                return 0;
+            }
+
             // check for cancellation request
             if (cancellationToken.IsCancellationRequested)
             {
@@ -194,6 +203,10 @@ internal async Task<int> ReadBufferAsync(byte[] buffer, int offset, int bytesToR
                 // catch everything else, doesn't matter
                 return 0;
             }
+            finally
+            {
+                _receiveSemaphore.Release();
+            }
 
             return bytesToReadRequested - bytesToRead;
         }