From cae7206733052918f32b5d7348a63697c149977e Mon Sep 17 00:00:00 2001
From: Christian <6939810+chkr1011@users.noreply.github.com>
Date: Wed, 6 Sep 2023 20:08:13 +0200
Subject: [PATCH] Fix NullReferenceException when calling Ping (#1834)

* Check connection status before doing ping

* Fix broken reconnect sample

* Update ReleaseNotes.md
---
 .github/workflows/ReleaseNotes.md           | 1 +
 Samples/Client/Client_Connection_Samples.cs | 3 +++
 Source/MQTTnet/Client/MqttClient.cs         | 9 +++++++--
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ReleaseNotes.md b/.github/workflows/ReleaseNotes.md
index e69de29bb..a3c59fc92 100644
--- a/.github/workflows/ReleaseNotes.md
+++ b/.github/workflows/ReleaseNotes.md
@@ -0,0 +1 @@
+* [Client] Fixed NullReferenceExeption when performing a Ping when the client is not connected (#1831).
diff --git a/Samples/Client/Client_Connection_Samples.cs b/Samples/Client/Client_Connection_Samples.cs
index 6fca63398..5c1f65112 100644
--- a/Samples/Client/Client_Connection_Samples.cs
+++ b/Samples/Client/Client_Connection_Samples.cs
@@ -430,6 +430,9 @@ public static void Reconnect_Using_Timer()
                         }
                     }
                 });
+
+            Console.WriteLine("Press <Enter> to exit");
+            Console.ReadLine();
         }
     }
 }
\ No newline at end of file
diff --git a/Source/MQTTnet/Client/MqttClient.cs b/Source/MQTTnet/Client/MqttClient.cs
index 02d551f41..a62530643 100644
--- a/Source/MQTTnet/Client/MqttClient.cs
+++ b/Source/MQTTnet/Client/MqttClient.cs
@@ -238,6 +238,11 @@ public async Task DisconnectAsync(MqttClientDisconnectOptions options, Cancellat
 
         public async Task PingAsync(CancellationToken cancellationToken = default)
         {
+            cancellationToken.ThrowIfCancellationRequested();
+            
+            ThrowIfDisposed();
+            ThrowIfNotConnected();
+
             if (cancellationToken.CanBeCanceled)
             {
                 await Request<MqttPingRespPacket>(MqttPingReqPacket.Instance, cancellationToken).ConfigureAwait(false);
@@ -441,7 +446,7 @@ async Task<MqttClientConnectResult> Authenticate(IMqttChannelAdapter channelAdap
 
                 if (receivedPacket is MqttConnAckPacket connAckPacket)
                 {
-                    result = MqttClientResultFactory.ConnectResult.Create(connAckPacket, _adapter.PacketFormatterAdapter.ProtocolVersion);
+                    result = MqttClientResultFactory.ConnectResult.Create(connAckPacket, channelAdapter.PacketFormatterAdapter.ProtocolVersion);
                 }
                 else if (receivedPacket is MqttAuthPacket)
                 {
@@ -513,7 +518,7 @@ async Task<MqttClientConnectResult> ConnectInternal(IMqttChannelAdapter channelA
             using (var effectiveCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(backgroundCancellationToken, cancellationToken))
             {
                 _logger.Verbose("Trying to connect with server '{0}'", Options.ChannelOptions);
-                await _adapter.ConnectAsync(effectiveCancellationToken.Token).ConfigureAwait(false);
+                await channelAdapter.ConnectAsync(effectiveCancellationToken.Token).ConfigureAwait(false);
                 _logger.Verbose("Connection with server established");
 
                 _publishPacketReceiverQueue?.Dispose();