Imagine coming home from work to find the lights automatically turned on, the air conditioning set to the most comfortable temperature, and your phone alerting you with a message saying “Living Room Temperature 26 ℃”. This is not magic, but rather the “group chat” completed in a second by MQTT—sensors act like chatterboxes, throwing data into a group called “Living Room/Temperature” where the lights, air conditioning, and phone are all participants, executing commands immediately upon receiving messages. What would happen if we used HTTP instead? You would first have to call the air conditioning: “What’s the temperature now?” The air conditioning would call back: “26.” Then you would call the lights: “Can you turn on?” The lights would call back: “I’m on.” After all this, you would be exhausted.
HTTP is like a traditional phone: you have to dial, wait, and hang up every time, even if you just want to say “Are you there?” You have to go through the complete etiquette, and the overhead is large enough to fit a love poem. MQTT, on the other hand, is like a never-disconnecting WeChat group: once connected, you can speak anytime, and messages are just tiny notes of two bytes that fly out and are immediately seen by all relevant devices; there’s no fear of disconnection, as it helps you cache offline messages and continues the conversation without losing a word.
Therefore, when you need an Internet of Things scenario that is “always online, instant synchronization, and power consumption down to milliamps,” let MQTT help you create a group; when you are just browsing the web or downloading images, the HTTP “phone call” etiquette remains appropriate. In short: for real-time group chats, use MQTT; for polite Q&A, use HTTP.