diff --git a/prj/TCPClient/Middle/QDXnetworkStack/qdx_port.c b/prj/TCPClient/Middle/QDXnetworkStack/qdx_port.c
index 627a29a..2836ff1 100644
--- a/prj/TCPClient/Middle/QDXnetworkStack/qdx_port.c
+++ b/prj/TCPClient/Middle/QDXnetworkStack/qdx_port.c
@@ -428,3 +428,20 @@ void qdx_port_tcp_close(qdx_socket_t sock)
     ring_init(&ctx->rx_ring);
     free_sock_ctx(ctx);
 }
+
+/* ============================================================
+ * WCHNET global lock — exposed for task_wchnet_entry in main.c
+ * All WCHNET API calls must be serialized through this mutex.
+ * ============================================================ */
+
+void qdx_port_net_lock(void)
+{
+    if (g_wchnet_mutex)
+        xSemaphoreTake(g_wchnet_mutex, portMAX_DELAY);
+}
+
+void qdx_port_net_unlock(void)
+{
+    if (g_wchnet_mutex)
+        xSemaphoreGive(g_wchnet_mutex);
+}
diff --git a/prj/TCPClient/User/main.c b/prj/TCPClient/User/main.c
index c9c558c..dc1c22d 100644
--- a/prj/TCPClient/User/main.c
+++ b/prj/TCPClient/User/main.c
@@ -168,6 +168,8 @@ extern void qdx_port_sock_recv_notify(uint8_t sockid);
 extern void qdx_port_sock_connect_notify(uint8_t sockid);
 extern void qdx_port_sock_disconnect_notify(uint8_t sockid);
 extern void qdx_port_init(void);
+extern void qdx_port_net_lock(void);
+extern void qdx_port_net_unlock(void);
 
 
 void WCHNET_HandleSockInt(u8 socketid, u8 intstat)
@@ -247,9 +249,11 @@ static void task_wchnet_entry(void *pvParameters)
     (void)pvParameters;
     while (1)
     {
+        qdx_port_net_lock();
         WCHNET_MainTask();
         if (WCHNET_QueryGlobalInt())
             WCHNET_HandleGlobalInt();
+        qdx_port_net_unlock();
         vTaskDelay(pdMS_TO_TICKS(5));
     }
 }