MQTT (Message Queuing Telemetry Transport) protocol was designed in 1999 for machine-to-machine (M2M) communication and recently gained its popularity also within Internet of Things (IoT) scenarios. The support for MQTT is also offered by SAP Cloud Platform.
MQTT is a lightweight messaging protocol based on publish-subscribe infrastructure. There is a central message broker and clients can connect to it to send and receive messages. With ABAP platform 1809 the MQTT protocol (Version 3.1.1) is also supported in ABAP stack. ABAP application server acts as a client and can publish messages and subscribe to the message broker to receive events.
The implementation of MQTT in ABAP platform is very similar to the existing ABAP channels infrastructure. ABAP platform offers the API to implement MQTT clients, which is event-driven, and contains the typical event handler methods like on_connect, on_message, on_subscribe etc. MQTT implementation in ABAP supports the following ABAP Push Channel connection types: WebSockets and TCP Sockets.
MQTT client is already used in the SAP product SAP Enterprise Messaging within its feature Enterprise Event Enablement, which allows to publish business events via MQTT. You can also use MQTT client in ABAP to develop event-driven extensions to SAP S/4HANA on SAP Cloud Platform.
Get your hands on MQTT in ABAP
For more details on MQTT see the official SAP Help documentation on MQTT Client.