MQTT vs HTTP Comparison: Which Protocol is Best for IoT?

1.Design and package

MQTT is data centric while HTTP is document centric. HTTP is a request-response protocol for client computers and is not always optimized for mobile devices. The main benefits of MQTT are compactness (MQTT transfers data as a byte array) and publisher/subscriber model, making it perfect for resource-constrained devices and helping to save energy.

Besides, the publisher / subscriber model provides customers with independent existence and improves the reliability of the whole system. When one customer is inactive, the entire system can continue to function normally.

2.Compare the speed of 2 protocols MQTT and HTTP

According to measurements in 3G networks, the throughput of MQTT is 93 times faster than HTTP.

In addition, compared to HTTP, the MQTT Protocol guarantees the highest quality of delivery.

There are 3 levels of Quality of Service (Qos):

• at most once (QoS = 0): ensure the best information delivery.
• at least once (QoS = 1): ensures that a message will be delivered at least once. But the message can also be sent more than once.
• exactly once (QoS = 2): ensures that each message is received only once by the counterparty.

MQTT also provides users with options for final and retained messages. This means that in the event of an unexpected client disconnection, all subscribed clients will receive a message from the broker.

Retained messages mean that a new customer subscriber will receive an immediate status update.

The HTTP protocol does not have these capabilities.

3.Message complexity and size

MQTT has a pretty short specification. Only the CONNECT, PUBOUND, SUBSCRIBE, UNSUBSCRIBE and DISCONNECT types make sense to developers. While the HTTP spec is much longer.

When comparing the message size between MQTT and HTTP : MQTT has a very short message header and the smallest packet message size is 2 bytes. Using the text message format using the HTTP protocol allows it to compose long headers and messages.

This eliminates the hassle as it is human readable, but at the same time, it is not necessary for devices that are resource constrained and only need to pass binary parameters.

The following table compares the MQTT and HTTP protocols.

Features and characteristics	MQTT	HTTP
Complete forms	Message queuing remotely	Hypertext Transfer Protocol
Design method	Protocol is data center	Protocol is the central document
Architecture	Publisher / Subscriber: Here devices can publish any topic and also subscribe to any updated topic.	Request/Response
Complexity	Simple	More complex
Data security	Have	Not yet secure, so HTTPS is used to provide security
Upper layer protocol	Runs on TCP	Run on UDP
Message size	Small, binary with header taking up 2 Bytes	Big, in ASCIILarge format, print ASCII format
Service Levels (QoS)	3	1
Library	30KB C, 100KB Java	Big
Port	1883	80 or 8080
Data partition	1 to 0/1/N	one to one

3.Conclusion

The MQTT protocol is very easy to use, responds well to unstable connection conditions, and low bandwidth. This makes MQTT very suitable for IoT applications.