MQTT full form is message queuing telemetry transport.
MQTT is the lightweight network protocol for resource-constrained devices. A low 2byte header and 256MB message size make the MQTT protocol a perfect use case for IoT/IIOT devices. MQTT Protocol is used in Smart home systems, smart cities, Industrial machines, vehicle tracking, and other applications. MQTT vs HTTP is important to understand to implement IoT applications.
MQTT works on the publish/subscribe pattern, it publishes a Topic with payload to MQTT Broker & then any of the other MQTT Clients can subscribe to the same topic. So, It’s not dependent on other clients if any of the clients stopped working.
Even LWT(Last will testament ) option would publish a message when an MQTT Client disconnected from the network to all the subscribed MQTT Clients.
There are 3 levels of quality of service(QoS) in MQTT
QoS 0 – at most once – ensures the best possible delivery without acknowledgment.
QoS 1 – at least once – ensures that the message must deliver at least once, but it can deliver more than once. It is the best possible method to be used with most of the applications to reduce network latency and usages.
QoS 2 – only once – ensures that the message reaches a subscriber & receives the acknowledgment until it publishes continuously.
Retained messages are the other functionality of MQTT where MQTT Broker retains the message with retain flag from MQTT Client and keep it retained until it has cleared with the retain flag.
MQTT vs HTTP shows the importance of IoT Applications as just QoS is important for MQTT to publish/subscribe the messages.
Read more about [Understanding retained messages](https://www.ioctrl.com/post/mqtt-retained-messages) in our other blog.
HTTP full form is Hypertext Transfer Protocol
HTTP is a universal web protocol used with HTML to communicate with web browsers. It needs more RAM & Power resources.
It is being used vastly for different applications that work in request/response patterns. It works in P2P(peer to peer) technology means the client/server model.
HTTP’s header size is large & response time is also more as compared to MQTT Protocol.
HTTP is used for high bandwidth & high payload applications as it is extendable.MQTT uses functions PUBLISH, SUBSCRIBE, CONNECT, DISCONNECT & UNSUBSCRIBE, but HTTP has huge library functions. MQTT secures the data layer with TLS/SSL, but HTTP secures it with HTTPS only. MQTT uses port 1883/8883, HTTP uses port 80.
HTTP uses base64 data structure HTTP transfer the data over UDP as compared to MQTT which uses TCP.
MQTT vs HTTP shows the importance of IoT Applications.
MQTT vs HTTP
IoT/IIOT Devices communicate with the cloud through MQTT/HTTP protocols. Both the protocols are perfect for IoT applications however, it depends on the use cases.
For example- if you would like to connect resource-constrained devices to the cloud, which requires less battery usage & low network bandwidth then MQTT is better to use as compared to HTTP. MQTT is specifically designed for M2M & IOT/IIOT applications.