MQTT (Message Queue Telemetry Transport) is a simple protocol on TCP/IP level. It is suitable for messaging between devices with minimum functionality and for transmission via unreliable networks. With the LMQTT library, the MQTT protocol is implemented in SIMATIC S7-1200/1500 Controllers.
Lean and fast: MQTT
MQTT 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 LMQTT library provides you with one function block for S7-1500 and S7-1200 CPUs. The “LMQTT_Client” function block integrates the MQTT client function and allows you to transmit MQTT messages to a broker (publisher role) and to create subscriptions (subscriber 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.