diff --git a/src/mms/inc_private/mms_client_internal.h b/src/mms/inc_private/mms_client_internal.h
index 86253325..45c64c25 100644
--- a/src/mms/inc_private/mms_client_internal.h
+++ b/src/mms/inc_private/mms_client_internal.h
@@ -79,8 +79,12 @@ struct sMmsConnection {
 	uint32_t connectTimeout;
 
 	IsoClientConnection isoClient;
-	AssociationState associationState;
-	ConnectionState connectionState;
+
+	volatile AssociationState associationState;
+	Semaphore associationStateLock;
+
+	volatile ConnectionState connectionState;
+	Semaphore connectionStateLock;
 
 	MmsConnectionParameters parameters;
 	IsoConnectionParameters isoParameters;
@@ -97,7 +101,8 @@ struct sMmsConnection {
 #endif
 
 	/* state of an active connection conclude/release process */
-	int concludeState;
+	volatile int concludeState;
+	Semaphore concludeStateLock;
 
 #if (MMS_OBTAIN_FILE_SERVICE == 1)
     int32_t nextFrsmId;
diff --git a/src/mms/iso_mms/client/mms_client_connection.c b/src/mms/iso_mms/client/mms_client_connection.c
index 7111b657..a9251905 100644
--- a/src/mms/iso_mms/client/mms_client_connection.c
+++ b/src/mms/iso_mms/client/mms_client_connection.c
@@ -39,6 +39,66 @@
 #define CONFIG_MMS_CONNECTION_DEFAULT_CONNECT_TIMEOUT 10000
 #define OUTSTANDING_CALLS 10
 
+static void
+setAssociationState(MmsConnection self, AssociationState newState)
+{
+    Semaphore_wait(self->associationStateLock);
+    self->associationState = newState;
+    Semaphore_post(self->associationStateLock);
+}
+
+static AssociationState
+getAssociationState(MmsConnection self)
+{
+    AssociationState state;
+
+    Semaphore_wait(self->associationStateLock);
+    state = self->associationState;
+    Semaphore_post(self->associationStateLock);
+
+    return state;
+}
+
+static void
+setConnectionState(MmsConnection self, ConnectionState newState)
+{
+    Semaphore_wait(self->connectionStateLock);
+    self->connectionState = newState;
+    Semaphore_post(self->connectionStateLock);
+}
+
+static ConnectionState
+getConnectionState(MmsConnection self)
+{
+    ConnectionState state;
+
+    Semaphore_wait(self->connectionStateLock);
+    state = self->connectionState;
+    Semaphore_post(self->connectionStateLock);
+
+    return state;
+}
+
+static void
+setConcludeState(MmsConnection self, int newState)
+{
+    Semaphore_wait(self->concludeStateLock);
+    self->concludeState = newState;
+    Semaphore_post(self->concludeStateLock);
+}
+
+static int
+getConcludeState(MmsConnection self)
+{
+    int state;
+
+    Semaphore_wait(self->concludeStateLock);
+    state = self->concludeState;
+    Semaphore_post(self->concludeStateLock);
+
+    return state;
+}
+
 static void
 handleUnconfirmedMmsPdu(MmsConnection self, ByteBuffer* message)
 {
@@ -310,7 +370,7 @@ sendRequestAndWaitForResponse(MmsConnection self, uint32_t invokeId, ByteBuffer*
     while (currentTime < waitUntilTime) {
         uint32_t receivedInvokeId;
 
-        if (self->associationState == MMS_STATE_CLOSED) {
+        if (getAssociationState(self) == MMS_STATE_CLOSED) {
             *mmsError = MMS_ERROR_CONNECTION_LOST;
             goto connection_lost;
         }
@@ -688,8 +748,8 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
     if (indication == ISO_IND_CLOSED) {
         if (DEBUG_MMS_CLIENT)
             printf("MMS_CLIENT: mmsIsoCallback: Connection lost or closed by client!\n");
-        self->connectionState = MMS_CON_IDLE;
-        self->associationState = MMS_STATE_CLOSED;
+        setConnectionState(self, MMS_CON_IDLE);
+        setAssociationState(self, MMS_STATE_CLOSED);
 
         /* Call user provided callback function */
         if (self->connectionLostHandler != NULL)
@@ -701,8 +761,8 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
     if (indication == ISO_IND_ASSOCIATION_FAILED) {
         if (DEBUG_MMS_CLIENT)
             printf("MMS_CLIENT: mmsIsoCallback: association failed!\n");
-        self->connectionState = MMS_CON_ASSOCIATION_FAILED;
-        self->associationState = MMS_STATE_CLOSED;
+        setConnectionState(self, MMS_CON_ASSOCIATION_FAILED);
+        setAssociationState(self, MMS_STATE_CLOSED);
         return;
     }
 
@@ -728,12 +788,12 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
         printf("MMS_CLIENT: MMS-PDU: %02x\n", tag);
 
     if (tag == 0xa9) { /* initiate response PDU */
-        if (indication == ISO_IND_ASSOCIATION_SUCCESS) {
-            self->connectionState = MMS_CON_ASSOCIATED;
-        }
-        else {
-            self->connectionState = MMS_CON_ASSOCIATION_FAILED;
-        }
+
+        if (indication == ISO_IND_ASSOCIATION_SUCCESS)
+            setConnectionState(self, MMS_CON_ASSOCIATED);
+        else
+            setConnectionState(self, MMS_CON_ASSOCIATION_FAILED);
+
         self->lastResponse = payload;
 
         IsoClientConnection_releaseReceiveBuffer(self->isoClient);
@@ -746,7 +806,7 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
         if (DEBUG_MMS_CLIENT)
             printf("MMS_CLIENT: received conclude.request\n");
 
-        self->concludeState = CONCLUDE_STATE_REQUESTED;
+        setConcludeState(self, CONCLUDE_STATE_REQUESTED);
 
         /* TODO block all new user requests? */
 
@@ -756,7 +816,7 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
         if (DEBUG_MMS_CLIENT)
             printf("MMS_CLIENT: received conclude.reponse+\n");
 
-        self->concludeState = CONCLUDE_STATE_ACCEPTED;
+        setConcludeState(self, CONCLUDE_STATE_ACCEPTED);
 
         IsoClientConnection_release(self->isoClient);
 
@@ -766,7 +826,7 @@ mmsIsoCallback(IsoIndication indication, void* parameter, ByteBuffer* payload)
         if (DEBUG_MMS_CLIENT)
             printf("MMS_CLIENT: received conclude.reponse-\n");
 
-        self->concludeState = CONCLUDE_STATE_REJECTED;
+        setConcludeState(self, CONCLUDE_STATE_REJECTED);
 
         IsoClientConnection_releaseReceiveBuffer(self->isoClient);
     }
@@ -1030,6 +1090,10 @@ MmsConnection_create()
     self->lastResponseLock = Semaphore_create(1);
     self->outstandingCallsLock = Semaphore_create(1);
 
+    self->connectionStateLock = Semaphore_create(1);
+    self->concludeStateLock = Semaphore_create(1);
+    self->associationStateLock = Semaphore_create(1);
+
     self->lastResponseError = MMS_ERROR_NONE;
 
     self->outstandingCalls = (uint32_t*) GLOBAL_CALLOC(OUTSTANDING_CALLS, sizeof(uint32_t));
@@ -1065,6 +1129,10 @@ MmsConnection_destroy(MmsConnection self)
     Semaphore_destroy(self->lastResponseLock);
     Semaphore_destroy(self->outstandingCallsLock);
 
+    Semaphore_destroy(self->associationStateLock);
+    Semaphore_destroy(self->connectionStateLock);
+    Semaphore_destroy(self->concludeStateLock);
+
     GLOBAL_FREEMEM(self->outstandingCalls);
 
 #if (MMS_OBTAIN_FILE_SERVICE == 1)
@@ -1172,7 +1240,7 @@ waitForConnectResponse(MmsConnection self)
     uint64_t waitUntilTime = currentTime + self->requestTimeout;
 
     while (currentTime < waitUntilTime) {
-        if (self->connectionState != MMS_CON_WAITING)
+        if (getConnectionState(self) != MMS_CON_WAITING)
             break;
 
         Thread_sleep(10);
@@ -1200,7 +1268,7 @@ MmsConnection_connect(MmsConnection self, MmsError* mmsError, const char* server
     }
 #endif /* (CONFIG_MMS_RAW_MESSAGE_LOGGING == 1) */
 
-    self->connectionState = MMS_CON_WAITING;
+    setConnectionState(self, MMS_CON_WAITING);
 
     IsoClientConnection_associate(self->isoClient, self->isoParameters, payload,
             self->connectTimeout);
@@ -1208,25 +1276,24 @@ MmsConnection_connect(MmsConnection self, MmsError* mmsError, const char* server
     waitForConnectResponse(self);
 
     if (DEBUG_MMS_CLIENT)
-        printf("MmsConnection_connect: received response conState: %i\n", self->connectionState);
+        printf("MmsConnection_connect: received response conState: %i\n", getConnectionState(self));
 
-    if (self->connectionState == MMS_CON_ASSOCIATED) {
+    if (getConnectionState(self) == MMS_CON_ASSOCIATED) {
         mmsClient_parseInitiateResponse(self);
 
         releaseResponse(self);
 
-        self->associationState = MMS_STATE_CONNECTED;
-    }
-    else {
-        self->associationState = MMS_STATE_CLOSED;
+        setAssociationState(self, MMS_STATE_CONNECTED);
     }
+    else
+        setAssociationState(self, MMS_STATE_CLOSED);
 
-    self->connectionState = MMS_CON_IDLE;
+    setConnectionState(self, MMS_CON_IDLE);
 
     if (DEBUG_MMS_CLIENT)
-        printf("MmsConnection_connect: states: con %i ass %i\n", self->connectionState, self->associationState);
+        printf("MmsConnection_connect: states: con %i ass %i\n", getConnectionState(self), getAssociationState(self));
 
-    if (self->associationState == MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) == MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_NONE;
         return true;
     }
@@ -1241,7 +1308,7 @@ MmsConnection_close(MmsConnection self)
 {
     self->connectionLostHandler = NULL;
 
-    if (self->associationState == MMS_STATE_CONNECTED)
+    if (getAssociationState(self) == MMS_STATE_CONNECTED)
         IsoClientConnection_close(self->isoClient);
 }
 
@@ -1254,7 +1321,7 @@ MmsConnection_abort(MmsConnection self, MmsError* mmsError)
 
     bool success = true;
 
-    if (self->associationState == MMS_STATE_CONNECTED)
+    if (getAssociationState(self) == MMS_STATE_CONNECTED)
         success = IsoClientConnection_abort(self->isoClient);
 
     if (success == false) {
@@ -1278,16 +1345,16 @@ sendConcludeRequestAndWaitForResponse(MmsConnection self)
 
     mmsClient_createConcludeRequest(self, concludeMessage);
 
-    self->concludeState = CONCLUDE_STATE_REQUESTED;
+    setConcludeState(self, CONCLUDE_STATE_REQUESTED);
 
     IsoClientConnection_sendMessage(self->isoClient, concludeMessage);
 
     while (currentTime < waitUntilTime) {
 
-        if (self->associationState == MMS_STATE_CLOSED)
+        if (getAssociationState(self) == MMS_STATE_CLOSED)
             goto exit_function;
 
-        if (self->concludeState != CONCLUDE_STATE_REQUESTED) {
+        if (getConcludeState(self) != CONCLUDE_STATE_REQUESTED) {
             success = true;
             break;
         }
@@ -1310,7 +1377,7 @@ exit_function:
 void
 MmsConnection_conclude(MmsConnection self, MmsError* mmsError)
 {
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1324,12 +1391,12 @@ MmsConnection_conclude(MmsConnection self, MmsError* mmsError)
 
     releaseResponse(self);
 
-    if (self->concludeState != CONCLUDE_STATE_ACCEPTED) {
+    if (getConcludeState(self) != CONCLUDE_STATE_ACCEPTED) {
 
-        if (self->associationState == MMS_STATE_CLOSED)
+        if (getAssociationState(self) == MMS_STATE_CLOSED)
             *mmsError = MMS_ERROR_CONNECTION_LOST;
 
-        if (self->concludeState == CONCLUDE_STATE_REJECTED)
+        if (getConcludeState(self) == CONCLUDE_STATE_REJECTED)
             *mmsError = MMS_ERROR_CONCLUDE_REJECTED;
     }
 
@@ -1359,7 +1426,7 @@ mmsClient_getNameListSingleRequest(
 {
     bool moreFollows = false;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1462,7 +1529,7 @@ MmsConnection_readVariable(MmsConnection self, MmsError* mmsError,
 {
     MmsValue* value = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1491,7 +1558,7 @@ MmsConnection_readArrayElements(MmsConnection self, MmsError* mmsError,
 {
     MmsValue* value = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1520,7 +1587,7 @@ MmsConnection_readMultipleVariables(MmsConnection self, MmsError* mmsError,
 {
     MmsValue* value = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1549,7 +1616,7 @@ MmsConnection_readNamedVariableListValues(MmsConnection self, MmsError* mmsError
 {
     MmsValue* value = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1580,7 +1647,7 @@ MmsConnection_readNamedVariableListValuesAssociationSpecific(
 {
     MmsValue* value = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1609,7 +1676,7 @@ MmsConnection_readNamedVariableListDirectory(MmsConnection self, MmsError* mmsEr
 {
     LinkedList attributes = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1639,7 +1706,7 @@ MmsConnection_readNamedVariableListDirectoryAssociationSpecific(MmsConnection se
 {
     LinkedList attributes = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1667,7 +1734,7 @@ void
 MmsConnection_defineNamedVariableList(MmsConnection self, MmsError* mmsError,
         const char* domainId, const char* listName, LinkedList variableSpecs)
 {
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1695,7 +1762,7 @@ void
 MmsConnection_defineNamedVariableListAssociationSpecific(MmsConnection self,
         MmsError* mmsError, const char* listName, LinkedList variableSpecs)
 {
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1726,7 +1793,7 @@ MmsConnection_deleteNamedVariableList(MmsConnection self, MmsError* mmsError,
 {
     bool isDeleted = false;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1755,7 +1822,7 @@ MmsConnection_deleteAssociationSpecificNamedVariableList(MmsConnection self,
 {
     bool isDeleted = false;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1785,7 +1852,7 @@ MmsConnection_getVariableAccessAttributes(MmsConnection self, MmsError* mmsError
 {
     MmsVariableSpecification* typeSpec = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }
@@ -1812,7 +1879,7 @@ MmsConnection_identify(MmsConnection self, MmsError* mmsError)
 {
     MmsServerIdentity* identity = NULL;
 
-    if (self->associationState != MMS_STATE_CONNECTED) {
+    if (getAssociationState(self) != MMS_STATE_CONNECTED) {
         *mmsError = MMS_ERROR_CONNECTION_LOST;
         goto exit_function;
     }