diff --git a/README.md b/README.md
index 2fd56d2..0c3bcf3 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,7 @@ enable EPEL Repo:
 # dnf install firewalld
 # firewall-cmd --add-service={http,https} --permanent
 # firewall-cmd --remove-service=cockpit --permanent
+# firewall-cmd --add-port=1883/tcp --permanent   ; only for MQTT
 # firewall-cmd --reload
 
 List Rules: