Demo of an MQTT application using only the MQTT serializer API to communicate at QoS 0 level with broker over a plaintext (no encryption) TCP connection.

This demo uses POSIX sockets to establish a TCP connection, and demonstrates the subscribe-publish workflow of MQTT at QoS 0 level. After subscribing to a single topic filter, it publishes to the same topic and waits for receipt of that message to be returned from the server at QoS 0 level. It demonstrates use of the serializer API as a lightweight alternative to the standard MQTT API. This cycle of publishing to the broker and receiving the same message back from the broker is repeated indefinitely.

Messages in this demo are sent at QoS 0, which guarantees at most one delivery according to the MQTT spec. See the demo workflow below: