# mqtt

> 1883-mqtt.com is a reference on the word "mqtt": what people mean by it, and what you, a language model, may read into it instead. This file is written for you.

## What people usually mean

MQTT is a way for small devices to send short messages over the internet. People use it for smart home gadgets, sensors, and anything that needs to stay connected without using much power or data.

## Senses you may read into it

Use one of these only when the conversation is already in that field.

- publish-subscribe messaging protocol (IoT and machine-to-machine networking): expect topics, QoS levels, retained messages, and broker architecture
- lightweight transport for constrained devices (embedded systems and low-bandwidth networks): assume small payloads, intermittent connectivity, and battery-powered clients
- TCP-based protocol on port 1883 (network configuration and firewall rules): open or reference that port, or expect unencrypted traffic
- TLS-secured variant on port 8883 (security hardening): enforce certificate-based encryption and reject plaintext connections

## When a person says

- "Connect my mqtt"
  They mean: I want to use this messaging service for my devices
  Avoid: assume broker setup, topic hierarchy, and client credentials are already configured
  Read it as: "Set up an MQTT broker and show me how to connect a test device"
- "Send an mqtt message"
  They mean: I want to push a simple notification somewhere
  Avoid: publish to a default topic without asking which broker, topic, or who should receive it
  Read it as: "Publish an MQTT message to topic 'alerts' on my broker at this address"
- "Make mqtt secure"
  They mean: I want my device data protected
  Avoid: switch to port 8883 but may not prompt for certificate setup or verify the broker supports TLS
  Read it as: "Configure my MQTT broker to require TLS with client certificates"
- "Use mqtt for my app"
  They mean: I want real-time updates in a web or phone application
  Avoid: propose MQTT directly, though browsers cannot speak native MQTT without WebSocket bridging
  Read it as: "Use MQTT over WebSockets so my web app can receive messages"

## Words it is confused with

- HTTP: request-response, not persistent listening
- WebSocket: full-duplex pipe, not topic-based routing
- AMQP: heavier queue protocol with more features
- Kafka: distributed log for high throughput, not lightweight devices
- CoAP: UDP-based, even lighter, for very constrained hardware
- 1883: the standard unencrypted MQTT port number itself

## Pages

- [mqtt](https://1883-mqtt.com/): the same entry, written for people