Here, I would like to share a MQTT Client Application Example for SIMATIC S7-1500 I created and tested with the following main features:

• Both Publisher and Subscriber are implemented
• Subscribe and unsubscribe for max. ten topics at a time (expandable)
• Handle max. ten incoming messages from the broker, arrived on the same packet (expandable)
• Demo project for HMI Comfort Panel is integrated
• Full QoS 0/1/2 handling mechanism
• Open code without know-how protection, free for use/modification
• Version for S7-1200 is also possible with minimum change of codes

Best regards,

Yu-wen

Dear SMJE,

Thanks a lot.

Yes, you are right. Siemens has made an "MQTT Publisher Application Example", as your link. But it's a MQTT "publisher", which can only "publish" message; neither "subscribe/unsusbcribe" messages nor receive messages from the broker are implemented.

This is exactly the reason why I create my version of  MQTT Client for my customer and share here.

The first point of my post has already highlighted the difference:

           - Both Publisher and Subscriber are implemented.

Best regards,

Yu-wen

Dear Yu-wen,

Your Implementation of subscription is secured?

Thanks in advance

Dear medea,

Yes, optional encryption of messages via SSL/TLS is possible. Please refer to the document attached to this Application Example (page 8):

Security function configuration

To activate the security functionality of the connection, the related parameters declared in the Static of the instance DB of MQTT_Client FB must be set according to your specifications.

Note:

The security function configuration is not included in the scope of this document. For secured communication via SSL/TLS, please refer to the chapter 3.6 of "SIMATIC S7-1500, ET 200MP, ET 200SP, ET 200AL, ET 200pro Communication Function Manual" (https://support.industry.siemens.com/cs/document/59192925/).

The information on the secured communication between MQTT broker and S7-1500 CPU via TLS can also be found in the chapter 2.3 of "MQTT Publisher for SIMATIC S7-1500" (https://support.industry.siemens.com/cs/document/109748872/)

Best regards,

Yu-wen

Very nice job and an even nicer documentation!

Thanks a lot!

Dear Yu-wen Tang,

Thank you so much for your quick reply