diff --git a/examples/mqttnet.c b/examples/mqttnet.c
index 53111939..6959fcdb 100644
--- a/examples/mqttnet.c
+++ b/examples/mqttnet.c
@@ -391,37 +391,66 @@ static int NetRead(void *context, byte* buf, int buf_len,
  * MQTT_CODE_CONTINUE, or proceed with a smaller buffer read/write.
  * Used for testing nonblocking. */
 static int
-mqttcurl_test_nonblock(int* buf_len, int for_recv)
+mqttcurl_test_nonblock_read(int* buf_len)
 {
-    static int testNbAlt = 0;
-    static int testSmallerBuf = 0;
-    #if !defined(WOLFMQTT_DEBUG_SOCKET)
-    (void)for_recv;
-    #endif
+    static int testNbReadAlt = 0;
+    static int testSmallerRead = 0;
+
+    if (testNbReadAlt < WOLFMQTT_TEST_NONBLOCK_TIMES) {
+        testNbReadAlt++;
+        #if defined(WOLFMQTT_DEBUG_SOCKET)
+        PRINTF("mqttcurl_test_nonblock_read: returning early with CONTINUE");
+        #endif
+        return MQTT_CODE_CONTINUE;
+    }
+
+    testNbReadAlt = 0;
+
+    if (!testSmallerRead) {
+        if (*buf_len > 2) {
+            *buf_len /= 2;
+            testSmallerRead = 1;
+        #if defined(WOLFMQTT_DEBUG_SOCKET)
+            PRINTF("mqttcurl_test_nonblock_read: testing small buff: %d",
+                   *buf_len);
+        #endif
+        }
+    }
+    else {
+        testSmallerRead = 0;
+    }
+
+    return MQTT_CODE_SUCCESS;
+}
 
-    if (testNbAlt < WOLFMQTT_TEST_NONBLOCK_TIMES) {
-        testNbAlt++;
+static int
+mqttcurl_test_nonblock_write(int* buf_len)
+{
+    static int testNbWriteAlt = 0;
+    static int testSmallerWrite = 0;
+
+    if (testNbWriteAlt < WOLFMQTT_TEST_NONBLOCK_TIMES) {
+        testNbWriteAlt++;
         #if defined(WOLFMQTT_DEBUG_SOCKET)
-        PRINTF("mqttcurl_test_nonblock(%d): returning early with CONTINUE",
-               for_recv);
+        PRINTF("mqttcurl_test_nonblock_write: returning early with CONTINUE");
         #endif
         return MQTT_CODE_CONTINUE;
     }
 
-    testNbAlt = 0;
+    testNbWriteAlt = 0;
 
-    if (!testSmallerBuf) {
+    if (!testSmallerWrite) {
         if (*buf_len > 2) {
             *buf_len /= 2;
-            testSmallerBuf = 1;
+            testSmallerWrite = 1;
         #if defined(WOLFMQTT_DEBUG_SOCKET)
-            PRINTF("mqttcurl_test_nonblock(%d): testing small buff: %d",
-                   for_recv, *buf_len);
+            PRINTF("mqttcurl_test_nonblock_write: testing small buff: %d",
+                   *buf_len);
         #endif
         }
     }
     else {
-        testSmallerBuf = 0;
+        testSmallerWrite = 0;
     }
 
     return MQTT_CODE_SUCCESS;
@@ -745,7 +774,7 @@ static int NetWrite(void *context, const byte* buf, int buf_len,
 
 #if defined(WOLFMQTT_NONBLOCK) && defined(WOLFMQTT_TEST_NONBLOCK)
     if (sock->mqttCtx->useNonBlockMode) {
-        if (mqttcurl_test_nonblock(&buf_len, 0)) {
+        if (mqttcurl_test_nonblock_write(&buf_len)) {
             return MQTT_CODE_CONTINUE;
         }
     }
@@ -773,8 +802,19 @@ static int NetWrite(void *context, const byte* buf, int buf_len,
      * payload will be transferred in a single shot without buffering.
      * todo: add buffering? */
     for (size_t i = 0; i < MQTT_CURL_NUM_RETRY; ++i) {
+    #ifdef WOLFMQTT_MULTITHREAD
+        int rc = wm_SemLock(&sock->mqttCtx->client.lockCURL);
+        if (rc != 0) {
+            return rc;
+        }
+    #endif
+
         res = curl_easy_send(sock->curl, buf, buf_len, &sent);
 
+    #ifdef WOLFMQTT_MULTITHREAD
+        wm_SemUnlock(&sock->mqttCtx->client.lockCURL);
+    #endif
+
         if (res == CURLE_OK) {
             #if defined(WOLFMQTT_DEBUG_SOCKET)
             PRINTF("info: curl_easy_send(%d) returned: %d, %s", buf_len, res,
@@ -828,7 +868,7 @@ static int NetRead(void *context, byte* buf, int buf_len,
 
 #if defined(WOLFMQTT_NONBLOCK) && defined(WOLFMQTT_TEST_NONBLOCK)
     if (sock->mqttCtx->useNonBlockMode) {
-        if (mqttcurl_test_nonblock(&buf_len, 1)) {
+        if (mqttcurl_test_nonblock_read(&buf_len)) {
             return MQTT_CODE_CONTINUE;
         }
     }
@@ -856,8 +896,19 @@ static int NetRead(void *context, byte* buf, int buf_len,
      * payload will be transferred in a single shot without buffering.
      * todo: add buffering? */
     for (size_t i = 0; i < MQTT_CURL_NUM_RETRY; ++i) {
+    #ifdef WOLFMQTT_MULTITHREAD
+        int rc = wm_SemLock(&sock->mqttCtx->client.lockCURL);
+        if (rc != 0) {
+            return rc;
+        }
+    #endif
+
         res = curl_easy_recv(sock->curl, buf, buf_len, &recvd);
 
+    #ifdef WOLFMQTT_MULTITHREAD
+        wm_SemUnlock(&sock->mqttCtx->client.lockCURL);
+    #endif
+
         if (res == CURLE_OK) {
             #if defined(WOLFMQTT_DEBUG_SOCKET)
             PRINTF("info: curl_easy_recv(%d) returned: %d, %s", buf_len, res,
diff --git a/src/mqtt_client.c b/src/mqtt_client.c
index f8e6b7d8..5aff6e80 100644
--- a/src/mqtt_client.c
+++ b/src/mqtt_client.c
@@ -1551,6 +1551,11 @@ int MqttClient_Init(MqttClient *client, MqttNet* net,
     if (rc == 0) {
         rc = wm_SemInit(&client->lockClient);
     }
+    #ifdef ENABLE_MQTT_CURL
+    if (rc == 0) {
+        rc = wm_SemInit(&client->lockCURL);
+    }
+    #endif
 #endif
 
     if (rc == 0) {
@@ -1573,6 +1578,9 @@ void MqttClient_DeInit(MqttClient *client)
         (void)wm_SemFree(&client->lockSend);
         (void)wm_SemFree(&client->lockRecv);
         (void)wm_SemFree(&client->lockClient);
+    #ifdef ENABLE_MQTT_CURL
+        (void)wm_SemFree(&client->lockCURL);
+    #endif
 #endif
     }
 #ifdef WOLFMQTT_V5
diff --git a/src/mqtt_socket.c b/src/mqtt_socket.c
index 03e062bb..ab68c426 100644
--- a/src/mqtt_socket.c
+++ b/src/mqtt_socket.c
@@ -64,7 +64,7 @@ int MqttSocket_TlsSocketReceive(WOLFSSL* ssl, char *buf, int sz,
     (void)ssl; /* Not used */
 
     rc = client->net->read(client->net->context, (byte*)buf, sz,
-        client->tls.timeout_ms);
+        client->tls.timeout_ms_read);
 
     /* save network read response */
     client->tls.sockRcRead = rc;
@@ -87,7 +87,7 @@ int MqttSocket_TlsSocketSend(WOLFSSL* ssl, char *buf, int sz,
     (void)ssl; /* Not used */
 
     rc = client->net->write(client->net->context, (byte*)buf, sz,
-        client->tls.timeout_ms);
+        client->tls.timeout_ms_write);
 
     /* save network write response */
     client->tls.sockRcWrite = rc;
@@ -116,7 +116,8 @@ int MqttSocket_Init(MqttClient *client, MqttNet *net)
     #if defined(ENABLE_MQTT_TLS) && !defined(ENABLE_MQTT_CURL)
         client->tls.ctx = NULL;
         client->tls.ssl = NULL;
-        client->tls.timeout_ms = client->cmd_timeout_ms;
+        client->tls.timeout_ms_read = client->cmd_timeout_ms;
+        client->tls.timeout_ms_write = client->cmd_timeout_ms;
     #endif
 
         /* Validate callbacks are not null! */
@@ -134,8 +135,9 @@ static int MqttSocket_WriteDo(MqttClient *client, const byte* buf, int buf_len,
 
 #if defined(ENABLE_MQTT_TLS) && !defined(ENABLE_MQTT_CURL)
     if (MqttClient_Flags(client,0,0) & MQTT_CLIENT_FLAG_IS_TLS) {
-        client->tls.timeout_ms = timeout_ms;
+        client->tls.timeout_ms_write = timeout_ms;
         client->tls.sockRcWrite = 0; /* init value */
+
         rc = wolfSSL_write(client->tls.ssl, (char*)buf, buf_len);
         if (rc < 0) {
         #if defined(WOLFMQTT_DEBUG_SOCKET) || defined(WOLFSSL_ASYNC_CRYPT)
@@ -236,8 +238,9 @@ static int MqttSocket_ReadDo(MqttClient *client, byte* buf, int buf_len,
 
 #if defined(ENABLE_MQTT_TLS) && !defined(ENABLE_MQTT_CURL)
     if (MqttClient_Flags(client,0,0) & MQTT_CLIENT_FLAG_IS_TLS) {
-        client->tls.timeout_ms = timeout_ms;
+        client->tls.timeout_ms_read = timeout_ms;
         client->tls.sockRcRead = 0; /* init value */
+
         rc = wolfSSL_read(client->tls.ssl, (char*)buf, buf_len);
         if (rc < 0) {
             int error = wolfSSL_get_error(client->tls.ssl, 0);
diff --git a/wolfmqtt/mqtt_client.h b/wolfmqtt/mqtt_client.h
index ddb70afe..d3789bce 100644
--- a/wolfmqtt/mqtt_client.h
+++ b/wolfmqtt/mqtt_client.h
@@ -209,6 +209,9 @@ typedef struct _MqttClient {
     wm_Sem lockSend;
     wm_Sem lockRecv;
     wm_Sem lockClient;
+    #ifdef ENABLE_MQTT_CURL
+    wm_Sem lockCURL;
+    #endif
     struct _MqttPendResp* firstPendResp; /* protected with client lock */
     struct _MqttPendResp* lastPendResp;  /* protected with client lock */
 #endif
diff --git a/wolfmqtt/mqtt_socket.h b/wolfmqtt/mqtt_socket.h
index cb1465e6..410c6c6b 100644
--- a/wolfmqtt/mqtt_socket.h
+++ b/wolfmqtt/mqtt_socket.h
@@ -71,7 +71,8 @@ typedef struct _MqttTls {
     WOLFSSL             *ssl;
     int                 sockRcRead;
     int                 sockRcWrite;
-    int                 timeout_ms;
+    int                 timeout_ms_read;
+    int                 timeout_ms_write;
 } MqttTls;
 #endif