diff --git a/session.cpp b/session.cpp
index 9b3a475..ae06448 100644
--- a/session.cpp
+++ b/session.cpp
@@ -90,11 +90,14 @@ std::unique_ptr<Session> Session::getCopy() const
     return s;
 }
 
-bool Session::clientDisconnected() const
-{
-    return client.expired();
-}
-
+/**
+ * @brief Session::makeSharedClient get the client of the session, or a null when it has no active current client.
+ * @return Returns shared_ptr<Client>, which can contain null when the client has disconnected.
+ *
+ * The lock() operation is atomic and therefore is the only way to get the current active client without race condition, because
+ * typically, this method is called from other client's threads to perform writes, so you have to check validity after
+ * obtaining the shared pointer.
+ */
 std::shared_ptr<Client> Session::makeSharedClient() const
 {
     return client.lock();
@@ -126,9 +129,10 @@ void Session::writePacket(const MqttPacket &packet, char max_qos, bool retain, u
     {
         if (qos == 0)
         {
-            if (!clientDisconnected())
+            std::shared_ptr<Client> c = makeSharedClient();
+
+            if (c)
             {
-                std::shared_ptr<Client> c = makeSharedClient();
                 c->writeMqttPacketAndBlameThisClient(packet, qos);
                 count++;
             }
@@ -150,9 +154,9 @@ void Session::writePacket(const MqttPacket &packet, char max_qos, bool retain, u
             std::shared_ptr<MqttPacket> copyPacket = qosPacketQueue.queuePacket(packet, nextPacketId);
             locker.unlock();
 
-            if (!clientDisconnected())
+            std::shared_ptr<Client> c = makeSharedClient();
+            if (c)
             {
-                std::shared_ptr<Client> c = makeSharedClient();
                 c->writeMqttPacketAndBlameThisClient(*copyPacket.get(), qos);
                 copyPacket->setDuplicate(); // Any dealings with this packet from here will be a duplicate.
                 count++;
@@ -183,9 +187,9 @@ uint64_t Session::sendPendingQosMessages()
 {
     uint64_t count = 0;
 
-    if (!clientDisconnected())
+    std::shared_ptr<Client> c = makeSharedClient();
+    if (c)
     {
-        std::shared_ptr<Client> c = makeSharedClient();
         std::lock_guard<std::mutex> locker(qosQueueMutex);
         for (const std::shared_ptr<MqttPacket> &qosMessage : qosPacketQueue)
         {
@@ -223,7 +227,7 @@ bool Session::hasExpired(int expireAfterSeconds)
 {
     std::chrono::seconds expireAfter(expireAfterSeconds);
     std::chrono::time_point<std::chrono::steady_clock> now = std::chrono::steady_clock::now();
-    return clientDisconnected() && (lastTouched + expireAfter) < now;
+    return client.expired() && (lastTouched + expireAfter) < now;
 }
 
 void Session::addIncomingQoS2MessageId(uint16_t packet_id)
diff --git a/session.h b/session.h
index ec2770e..c4c319d 100644
--- a/session.h
+++ b/session.h
@@ -66,7 +66,6 @@ public:
     std::unique_ptr<Session> getCopy() const;
 
     const std::string &getClientId() const { return client_id; }
-    bool clientDisconnected() const;
     std::shared_ptr<Client> makeSharedClient() const;
     void assignActiveConnection(std::shared_ptr<Client> &client);
     void writePacket(const MqttPacket &packet, char max_qos, bool retain, uint64_t &count);
diff --git a/subscriptionstore.cpp b/subscriptionstore.cpp
index 6628ebb..0922f27 100644
--- a/subscriptionstore.cpp
+++ b/subscriptionstore.cpp
@@ -212,13 +212,17 @@ void SubscriptionStore::registerClientAndKickExistingOne(std::shared_ptr<Client>
     {
         session = session_it->second;
 
-        if (session && !session->clientDisconnected())
+        if (session)
         {
             std::shared_ptr<Client> cl = session->makeSharedClient();
-            logger->logf(LOG_NOTICE, "Disconnecting existing client with id '%s'", cl->getClientId().c_str());
-            cl->setReadyForDisconnect();
-            cl->getThreadData()->removeClient(cl);
-            cl->markAsDisconnecting();
+
+            if (cl)
+            {
+                logger->logf(LOG_NOTICE, "Disconnecting existing client with id '%s'", cl->getClientId().c_str());
+                cl->setReadyForDisconnect();
+                cl->getThreadData()->removeClient(cl);
+                cl->markAsDisconnecting();
+            }
         }
     }
 
@@ -255,10 +259,9 @@ void SubscriptionStore::publishNonRecursively(const MqttPacket &packet, const st
 {
     for (const Subscription &sub : subscribers)
     {
-        std::weak_ptr<Session> session_weak = sub.session;
-        if (!session_weak.expired()) // Shared pointer expires when session has been cleaned by 'clean session' connect.
+        const std::shared_ptr<Session> session = sub.session.lock();
+        if (session) // Shared pointer expires when session has been cleaned by 'clean session' connect.
         {
-            const std::shared_ptr<Session> session = session_weak.lock();
             session->writePacket(packet, sub.qos, false, count);
         }
     }
@@ -469,7 +472,8 @@ int SubscriptionNode::cleanSubscriptions()
     auto it = subscribers.begin();
     while (it != subscribers.end())
     {
-        if (it->sessionGone())
+        std::shared_ptr<Session> ses = it->session.lock();
+        if (!ses)
         {
             Logger::getInstance()->logf(LOG_DEBUG, "Removing empty spot in subscribers vector");
             it = subscribers.erase(it);
@@ -539,9 +543,10 @@ void SubscriptionStore::getSubscriptions(SubscriptionNode *this_node, const std:
 {
     for (const Subscription &node : this_node->getSubscribers())
     {
-        if (!node.sessionGone())
+        std::shared_ptr<Session> ses = node.session.lock();
+        if (ses)
         {
-            SubscriptionForSerializing sub(node.session.lock()->getClientId(), node.qos);
+            SubscriptionForSerializing sub(ses->getClientId(), node.qos);
             outputList[composedTopic].push_back(sub);
         }
     }
@@ -702,7 +707,7 @@ bool Subscription::operator==(const Subscription &rhs) const
     const std::shared_ptr<Session> lhs_ses = session.lock();
     const std::shared_ptr<Session> rhs_ses = rhs.session.lock();
 
-    return lhs_ses->getClientId() == rhs_ses->getClientId();
+    return lhs_ses && rhs_ses && lhs_ses->getClientId() == rhs_ses->getClientId();
 }
 
 void Subscription::reset()
@@ -711,11 +716,6 @@ void Subscription::reset()
     qos = 0;
 }
 
-bool Subscription::sessionGone() const
-{
-    return session.expired();
-}
-
 void RetainedMessageNode::addPayload(const std::string &topic, const std::string &payload, char qos, int64_t &totalCount)
 {
     const int64_t countBefore = retainedMessages.size();
diff --git a/subscriptionstore.h b/subscriptionstore.h
index 93e3dc6..078aad5 100644
--- a/subscriptionstore.h
+++ b/subscriptionstore.h
@@ -39,7 +39,6 @@ struct Subscription
     char qos;
     bool operator==(const Subscription &rhs) const;
     void reset();
-    bool sessionGone() const;
 };
 
 class SubscriptionNode