This is a project for an app which should simulate a sensor on an Android device.
Also it can be an Android replacement for mosquitto_pub (or later also for mosquitto_sub)
Key words:
IoT platforms to publish on them:
Citation from https://blogs.oracle.com/javamagazine/post/java-mqtt-iot-message-queuing :
There are quite a few MQTT brokers available under varying license models. Additionally, there are cloud services that support MQTT integration, such as Oracle Internet of Things Production Monitoring Cloud Service and Oracle Internet of Things Cloud Service.
The following are a few open source MQTT implementations: