Mitsubishi Electric MELSEC iQ-F Series User Manual page 54

■Connecting to a broker (Connect)
• For TCP connection
FX5 CPU module
(ladder program)
To connect to a broker, the MQTT client (Ethernet module) sends the CONNECT command to a broker.
When a session is established, the broker returns CONNACK and allows publishing and subscribing. Generally, when using
TCP connection (not using TLS connection), TCP port 1883 is used. Other ports can be used if they are supported by the
broker.
When a firewall is set up between this Ethernet module and the Internet, permission must be given to a port to be used. Set
permission according to the instructions by the system administrator.
A user name and password can be included in the CONNECT command. Brokers can provide their own authentication
mechanism, and the authentication mechanism of the OS (local) can be used. However, if TLS connection is not used and the
above authentication data is not obfuscated, man-in-the-middle attacks or replay attacks may be made.
4 FUNCTION LIST
52
4.3 Other Functions
FB: MQTT_Connect FB: MQTT_Connect
i_bConnect=OFF→ON i_bConnect=OFF→ON
FB: MQTT_Connect: return FB: MQTT_Connect: return
o_bOK=ON o_bOK=ON
Ethernet module
CONNECT (ClientID, Username, Password) CONNECT (ClientID, Username, Password)
CONNACK CONNACK
Broker