What is MQTT and how it Works?

A Publish Subscribe Messaging protocol allowing a message to be published once and multiple consumers (application / devices) to receive message providing decoupling between the producer and consumer.

Ø  A Producer sends (publishes) a message (publication) on a topic (subject).

Ø  A consumer subscribes (makes a subscription) for messages on a topic (subject).

Ø  A Message server or broker matches publications to subscriptions.

·         If no matches the message is discarded.

·         If one or more matches the message is delivered to each messaging subscriber or consumer.

MQTT Model:

1)    MQTT Client:

                MQTT client plays the role of both publisher and subscriber. MQTT Client subscribes to topics to publish and receive messages. Hence the Subscriber and Publisher are two different roles that a client can play. This client application can collect data from the telemetry device connects to a message server or broker and uses a topic to publish the message which can be used by other clients or applications to receive it.

Few Famous MQTT clients:

Websphere MQ Telemetry clients: It comes along with IBM Websphere MQ version starting from 7.1. This is a precompiled MQTT client which supports the implementation of MQTT 3.1 protocol. It is a licensed version.

Eclipse Paho Clients: This is an open source MQTT client for M2M communication with C and Java based implementations of MQTT. This is an open source.

2)    MQTT Server or MQTT Broker:

                MQTT Server or broker which run topics i.e. A server can receive subscriptions from clients on topics, it can receive messages from clients and forward these messages to the interested clients based on client’s subscriptions.MQTT brokers are the mediator which implements the MQTT protocol and mediates between MQTT clients and the enterprise integration layer.