diff --git a/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketReader.cs b/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketReader.cs
index ef07848..5359d99 100644
--- a/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketReader.cs
+++ b/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketReader.cs
@@ -24,14 +24,17 @@ namespace MQTTnet.Serializer
 
         public static async Task<MqttPacketHeader> ReadHeaderFromSourceAsync(Stream stream, CancellationToken cancellationToken)
         {
-            byte[] singleByteBuf = new byte[1];
-            var readCount = await stream.ReadAsync(singleByteBuf, 0, singleByteBuf.Length).ConfigureAwait(false);
+            // Wait for the next package which starts with the header. At this point there will probably
+            // some large delay and thus the thread should be put back to the pool (await). So ReadByte()
+            // is not an option here.
+            var buffer = new byte[1];
+            var readCount = await stream.ReadAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
             if (readCount <= 0)
             {
                 return null;
             }
 
-            var fixedHeader = singleByteBuf[0];
+            var fixedHeader = buffer[0];
             var controlPacketType = (MqttControlPacketType)(fixedHeader >> 4);
             var bodyLength = await ReadBodyLengthFromSourceAsync(stream, cancellationToken).ConfigureAwait(false);
 
@@ -88,8 +91,7 @@ namespace MQTTnet.Serializer
             var value = 0;
             byte encodedByte;
 
-            byte[] singleByteBuf = new byte[1];
-
+            var buffer = new byte[1];
             var readBytes = new List<byte>();
             do
             {
@@ -98,13 +100,13 @@ namespace MQTTnet.Serializer
                     throw new TaskCanceledException();
                 }
 
-                int readCount = await stream.ReadAsync(singleByteBuf, 0, singleByteBuf.Length).ConfigureAwait(false);
+                var readCount = await stream.ReadAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
                 if (readCount <= 0)
                 {
                     throw new MqttCommunicationException("Connection closed while reading remaining length data.");
                 }
 
-                encodedByte = singleByteBuf[0];
+                encodedByte = buffer[0];
                 readBytes.Add(encodedByte);
 
                 value += (byte)(encodedByte & 127) * multiplier;
diff --git a/Frameworks/MQTTnet.NetStandard/Server/MqttClientPendingMessagesQueue.cs b/Frameworks/MQTTnet.NetStandard/Server/MqttClientPendingMessagesQueue.cs
index e092d3b..62a4d78 100644
--- a/Frameworks/MQTTnet.NetStandard/Server/MqttClientPendingMessagesQueue.cs
+++ b/Frameworks/MQTTnet.NetStandard/Server/MqttClientPendingMessagesQueue.cs
@@ -43,6 +43,7 @@ namespace MQTTnet.Server
 
             _queue.Enqueue(packet);
             _queueWaitSemaphore.Release();
+
             _logger.Trace<MqttClientPendingMessagesQueue>("Enqueued packet (ClientId: {0}).", _session.ClientId);
         }
 
@@ -70,9 +71,11 @@ namespace MQTTnet.Server
             try
             {
                 await _queueWaitSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
-                if (!_queue.TryDequeue(out packet)) {
+                if (!_queue.TryDequeue(out packet))
+                {
                     throw new InvalidOperationException(); // should not happen
                 }
+
                 await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, packet).ConfigureAwait(false);
 
                 _logger.Trace<MqttClientPendingMessagesQueue>("Enqueued packet sent (ClientId: {0}).", _session.ClientId);
diff --git a/Tests/MQTTnet.Core.Tests/MqttClientTests.cs b/Tests/MQTTnet.Core.Tests/MqttClientTests.cs
new file mode 100644
index 0000000..d434325
--- /dev/null
+++ b/Tests/MQTTnet.Core.Tests/MqttClientTests.cs
@@ -0,0 +1,37 @@
+using System;
+using System.Net.Sockets;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Client;
+using MQTTnet.Exceptions;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class MqttClientTests
+    {
+
+        [TestMethod]
+        public async Task ClientDisconnectException()
+        {
+            var factory = new MqttFactory();
+            var client = factory.CreateMqttClient();
+
+            var exceptionIsCorrect = false;
+            client.Disconnected += (s, e) =>
+            {
+                exceptionIsCorrect = e.Exception is MqttCommunicationException c && c.InnerException is SocketException;
+            };
+
+            try
+            {
+                await client.ConnectAsync(new MqttClientOptionsBuilder().WithTcpServer("wrong-server").Build());
+            }
+            catch
+            {
+            }
+            
+            Assert.IsTrue(exceptionIsCorrect);
+        }
+    }
+}
diff --git a/Tests/MQTTnet.Core.Tests/MqttPacketReaderTests.cs b/Tests/MQTTnet.Core.Tests/MqttPacketReaderTests.cs
index 606d1da..4d0e9b0 100644
--- a/Tests/MQTTnet.Core.Tests/MqttPacketReaderTests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttPacketReaderTests.cs
@@ -12,7 +12,7 @@ namespace MQTTnet.Core.Tests
         public void MqttPacketReader_EmptyStream()
         {
             var memStream = new MemoryStream();
-            var header = MqttPacketReader.ReadHeaderFromSource(memStream, CancellationToken.None);
+            var header = MqttPacketReader.ReadHeaderFromSourceAsync(memStream, CancellationToken.None).GetAwaiter().GetResult();
 
             Assert.IsNull(header);
         }
diff --git a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
index 9f51b86..5a75490 100644
--- a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
@@ -405,7 +405,7 @@ namespace MQTTnet.Core.Tests
 
             using (var headerStream = new MemoryStream(Join(buffer1)))
             {
-                var header = MqttPacketReader.ReadHeaderFromSource(headerStream, CancellationToken.None);
+                var header = MqttPacketReader.ReadHeaderFromSourceAsync(headerStream, CancellationToken.None).GetAwaiter().GetResult();
 
                 using (var bodyStream = new MemoryStream(Join(buffer1), (int)headerStream.Position, header.BodyLength))
                 {