Ignore Acknowledge with invalid Code Class

src/CoAPNet/CoapClient.cs

@@ -198,6 +198,10 @@ await SendAsync(new CoapMessage
                                 Type = CoapMessageType.Reset
                             }, payload.Endpoint);
                         }
+                        if (message.Type == CoapMessageType.Acknowledgement
+                            && Coap.ReservedMessageCodeClasses.Contains(message.Code.Class))
+                            continue;
+
                         throw;
                     }
 
@@ -279,7 +283,7 @@ public void Dispose()
                 throw new ArgumentOutOfRangeException($"The current message id ({messageId}) is not pending a due response");
 
             if (responseTask.Task.IsCompleted)
-                return responseTask.Task.Result;
+                return await responseTask.Task;
 
             if (Endpoint == null)
                 throw new InvalidOperationException($"{nameof(CoapClient)} is in an invalid state");

src/CoAPNet/CoapMessage.cs

@@ -353,7 +353,7 @@ public void FromBytes(byte[] data)
             }
 
             // Performing this check after parsing the options to allow the chance of reading the message token
-            if (new int[] {1, 6, 7}.Contains(Code.Class))
+            if (Coap.ReservedMessageCodeClasses.Contains(Code.Class))
                 throw new CoapMessageFormatException("Message.Code can not use reserved classes");
 
             if (badOptions.Count == 1)

src/CoAPNet/Constants.cs

@@ -85,5 +85,7 @@ public static string GetMulticastIPv6ForScope(int scope)
                 throw new ArgumentOutOfRangeException(nameof(scope), "Scope must be in the range from 1 to 14. 0 and 15 are reserved. (See RFC 7346)");
             return MulticastIPv6.Replace("X", scope.ToString("X"));
         }
+
+        public static readonly int[] ReservedMessageCodeClasses = new int[] { 1, 6, 7 };
     }
 }

tests/CoAPNet.Tests/CoapClientTests.cs

@@ -448,9 +448,39 @@ public async Task TestIgnoreNonEmptyResetMessages()
         // TODO: Test Ignore Acknowledgement Messages With Reserved Code
         [Test]
         [Category("[RFC7252] Section 4.2")]
-        public void TestIgnoreAcknowledgementMessagesWithReservedCode()
+        public async Task TestIgnoreAcknowledgementMessagesWithReservedCode()
         {
-            Assert.Inconclusive("Not Implemented");
+            // Arrange
+            var mockClientEndpoint = new Mock<MockEndpoint> { CallBase = true };
+
+            var expected = new CoapMessage
+            {
+                Id = 0x1234,
+                Type = CoapMessageType.Acknowledgement,
+                Code = new CoapMessageCode(1, 0),
+                Options = new System.Collections.Generic.List<CoapOption>
+                    {
+                        new Options.ContentFormat(Options.ContentFormatType.ApplicationLinkFormat)
+                    },
+                Payload = Encoding.UTF8.GetBytes("</.well-known/core>")
+            };
+
+            mockClientEndpoint
+                .SetupSequence(c => c.MockReceiveAsync())
+                .Returns(Task.FromResult(new CoapPacket { Payload = expected.ToBytes() }))
+                .Returns(Task.Delay(2000).ContinueWith<CoapPacket>(_ => throw new CoapEndpointException("Endpoint closed")));
+
+            // Ack
+            using (var client = new CoapClient(mockClientEndpoint.Object))
+            {
+                var ct = new CancellationTokenSource(MaxTaskTimeout);
+                client.RetransmitTimeout = TimeSpan.FromMilliseconds(200);
+                client.MaxRetransmitAttempts = 3;
+                client.SetNextMessageId(0x1234);
+
+                // Assert
+                Assert.ThrowsAsync<CoapClientException>(async () => await client.GetAsync("coap://example.com/.well-known/core", ct.Token));
+            }
         }
 
         // TODO: Test Reached Max Failed Retransmit Attempts