Only update the native library and the c# calls that need to be made to clean up channels. (#5283)

Author: maryamhonari

com.unity.ml-agents/Plugins/ProtoBuffer/runtimes/osx/native/libgrpc_csharp_ext.x64.bundle

@@ -1,6 +1,9 @@
 # if UNITY_EDITOR || UNITY_STANDALONE_WIN || UNITY_STANDALONE_OSX || UNITY_STANDALONE_LINUX
 using Grpc.Core;
 #endif
+
+#if MLA_SUPPORTED_TRAINING_PLATFORM
+using Grpc.Core;
 #if UNITY_EDITOR
 using UnityEditor;
 #endif
@@ -49,9 +52,7 @@ internal class RpcCommunicator : ICommunicator
 # if UNITY_EDITOR || UNITY_STANDALONE_WIN || UNITY_STANDALONE_OSX || UNITY_STANDALONE_LINUX
         /// The Unity to External client.
         UnityToExternalProto.UnityToExternalProtoClient m_Client;
-#endif
-        /// The communicator parameters sent at construction
-        CommunicatorInitParameters m_CommunicatorInitParameters;
+        Channel m_Channel;
 
         /// <summary>
         /// Initializes a new instance of the RPCCommunicator class.
@@ -231,6 +232,10 @@ public UnityRLInitParameters Initialize(CommunicatorInitParameters initParameter
                     );
                     throw new UnityAgentsException("Incompatible trainer version.");
                 }
+                initParametersOut = new UnityRLInitParameters();
+                m_Channel.ShutdownAsync().Wait();
+                return false;
+            }
 
                 var packageVersionSupported = CheckPythonPackageVersionIsSupported(pythonPackageVersion);
                 if (!packageVersionSupported)
@@ -262,7 +267,14 @@ public UnityRLInitParameters Initialize(CommunicatorInitParameters initParameter
             }
 
             UpdateEnvironmentWithInput(input.RlInput);
-            return initializationInput.RlInitializationInput.ToUnityRLInitParameters();
+            initParametersOut = initializationInput.RlInitializationInput.ToUnityRLInitParameters();
+            // Be sure to shut down the grpc channel when the application is quitting.
+            Application.quitting += NotifyQuitAndShutDownChannel;
+            return true;
+#else
+            initParametersOut = new UnityRLInitParameters();
+            return false;
+#endif
         }
 
         /// <summary>
@@ -296,24 +308,33 @@ UnityInputProto Initialize(UnityOutputProto unityOutput,
         {
 # if UNITY_EDITOR || UNITY_STANDALONE_WIN || UNITY_STANDALONE_OSX || UNITY_STANDALONE_LINUX
             m_IsOpen = true;
-            var channel = new Channel(
-                "localhost:" + m_CommunicatorInitParameters.port,
-                ChannelCredentials.Insecure);
+            m_Channel = new Channel($"localhost:{port}", ChannelCredentials.Insecure);
 
-            m_Client = new UnityToExternalProto.UnityToExternalProtoClient(channel);
+            m_Client = new UnityToExternalProto.UnityToExternalProtoClient(m_Channel);
             var result = m_Client.Exchange(WrapMessage(unityOutput, 200));
             unityInput = m_Client.Exchange(WrapMessage(null, 200)).UnityInput;
 #if UNITY_EDITOR
             EditorApplication.playModeStateChanged += HandleOnPlayModeChanged;
 #endif
+            if (result.Header.Status != 200 || inputMessage.Header.Status != 200)
+            {
+                m_IsOpen = false;
+                NotifyQuitAndShutDownChannel();
+            }
             return result.UnityInput;
 #else
             throw new UnityAgentsException(
                 "You cannot perform training on this platform.");
 #endif
         }
 
-        #endregion
+        void NotifyQuitAndShutDownChannel()
+        {
+            QuitCommandReceived?.Invoke();
+            m_Channel.ShutdownAsync().Wait();
+        }
+
+#endregion
 
         #region Destruction
 
@@ -352,10 +373,10 @@ void SendCommandEvent(CommandProto command)
             switch (command)
             {
                 case CommandProto.Quit:
-                {
-                    QuitCommandReceived?.Invoke();
-                    return;
-                }
+                    {
+                        NotifyQuitAndShutDownChannel();
+                        return;
+                    }
                 case CommandProto.Reset:
                 {
                     foreach (var brainName in m_OrderedAgentsRequestingDecisions.Keys)
@@ -540,13 +561,13 @@ UnityInputProto Exchange(UnityOutputProto unityOutput)
                 // Not sure if the quit command is actually sent when a
                 // non 200 message is received.  Notify that we are indeed
                 // quitting.
-                QuitCommandReceived?.Invoke();
+                NotifyQuitAndShutDownChannel();
                 return message.UnityInput;
             }
             catch
             {
                 m_IsOpen = false;
-                QuitCommandReceived?.Invoke();
+                NotifyQuitAndShutDownChannel();
                 return null;
             }
 #else