In this blog, we will implement a simple MQTT client using lwIP's MQTT library, providing a reference for those who want to develop MQTT services and applications based on lwIP.

This blog will provide a step-by-step guide on how to connect a serverless MQTT broker in React using the MQTT.js library.

The Message Expiry Interval is a new feature introduced in MQTT 5.0, which allows the publisher to set an expiry interval for time-sensitive messages.

To achieve the Enhanced Authentication, MQTT introduced the AUTH packet to implement any number of authentication data exchanges, to support various types of authentication mechanisms, such as SCRAM, Kerberos authentication, and so on.

In MQTT, both the client and the server can send a DISCONNECT packet to the other party before disconnecting the network connection, indicating the reason for the connection closure.

MQTT has a type of packet used to simulate heartbeats between the client and server to maintain the connection. They are PINGREQ and PINGRESP packets, which we often call heartbeat packets.

In MQTT, the SUBSCRIBE packet is used to initiate a subscription request, while the SUBACK packet is used to return the subscription result. The UNSUBSCRIBE and UNSUBACK packets are used when unsubscribing.

This blog will introduces the PUBLISH packet used to deliver application messages in MQTT, and its response packets.

RabbitMQ is an open-source message-broker software that transmits data between applications and services. Kafka is an open-source distributed message streaming platform.

MQTT connection requires CONNECT and CONNACK packets. CONNECT initiates the request and server responds with CONNACK indicating connection result.

This blog will introduce each new feature introduced in 5.0 in turn, and use the MQTTX CLI tool to demonstrate how we can use these features in EMQX.

This blog provides a simple Unity3d project for using M2MQTT with Unity. The project includes an example scene with a user interface for managing the connection to the broker and testing messaging.