MQTT Publisher for SIMATIC CPU
The “Message Queue Telemetry Transport” is a simply structured binary Publish/ Subscribe protocol on TCP/IP level. It is suitable for messaging between devices with minimum functionality and for transmission via unreliable networks with low bandwith and high latency. With these characteristics, MQTT plays a vital role for the IoT and in M2M communication.
The application example provides you with a function block for the SIMATIC CPU. The “LMqtt_Publisher” function block integrates the MQTT client function and allows you to transmit MQTT messages to a broker (publisher role). In this, the communication can be secured via a TLS connection. You can reach the broker with a static ip address or a qualified domain name.
The following picture shows the secure mqtt-messaging with a SIMATIC S7-1500.
Advantages of MQTT
The MQTT protocol stands out with the following characteristics:
Light-weight protocol with low transport overhead
Minimum requirement for network bandwith thanks to push mechanism
Function for re-connecting after disconnection
Re-sending messages after disconnection
Mechanism for notifying interested parties after an unpredicted disconnection of a client
Simple use and implementation thanks to a small set of commands
Quality of Service (QoS level) with different reliability levels for the message delivery
Optional encryption of messages via SSL/TLS
Authentification of publishers and subscribers via user name and password
Documentation and project example for an unsecure messaging (S7-1500, S7-1200, S7-300)
Library for S7-1200 / S7-1500 (TIA Portal V15) (1,7 MB)
Library for S7-300 (TIA Portal V15) (956,6 KB)
Documentation (1,3 MB)
In the archive you find the old libraries for TIA Portal V14 SP1
Archive (2,1 MB)
Integration of the variant, to reach the broker with a qualified domain name.