From b38df9eecd1bc6416816664e6388baa406112dcf Mon Sep 17 00:00:00 2001
From: Christoph Stichlberger <christoph.stichlberger@copadata.com>
Date: Mon, 4 Jun 2018 16:00:03 +0200
Subject: [PATCH] Respect keep alive interval after sending

---
 Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs b/Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs
index 90790d5a..ae8442ee 100644
--- a/Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs
+++ b/Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs
@@ -419,12 +419,14 @@ namespace MQTTnet.Client
                         keepAliveSendInterval = _options.KeepAliveSendInterval.Value;
                     }
 
-                    if (_sendTracker.Elapsed > keepAliveSendInterval)
+                    var waitTime = keepAliveSendInterval - _sendTracker.Elapsed;
+                    if (waitTime <= TimeSpan.Zero)
                     {
                         await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket()).ConfigureAwait(false);
+                        waitTime = keepAliveSendInterval;
                     }
 
-                    await Task.Delay(keepAliveSendInterval, _cancellationTokenSource.Token).ConfigureAwait(false);
+                    await Task.Delay(waitTime, _cancellationTokenSource.Token).ConfigureAwait(false);
                 }
             }
             catch (Exception exception)