EMQX — Scalable MQTT Broker for IoT and Connected Devices

What it is

EMQX is an open-source MQTT message broker designed for large-scale IoT deployments. It implements MQTT 5.0 and 3.1.1 protocols and is built on the Erlang/OTP platform, which gives it strong concurrency and fault-tolerance characteristics. EMQX powers IoT platforms, connected vehicles, industrial automation, and smart city infrastructure.

The broker targets IoT architects, embedded engineers, and backend teams building systems that need reliable pub/sub messaging at scale. If your application involves thousands to millions of devices publishing telemetry, EMQX is built for that workload.

How it saves time or tokens

EMQX eliminates the need to build custom message routing, device authentication, and connection management for IoT. Instead of stitching together a message queue, a connection pool, and an auth layer, you get a single binary that handles all three. Its rule engine processes and routes messages without writing custom code, and built-in integrations push data to databases and cloud services directly.

How to use

1. Run EMQX with Docker:

docker run -d --name emqx \
  -p 1883:1883 -p 8083:8083 \
  -p 8084:8084 -p 8883:8883 \
  -p 18083:18083 \
  emqx/emqx:latest

1. Access the dashboard at http://localhost:18083 with default credentials (admin / public).

1. Connect an MQTT client to port 1883 and start publishing messages.

1. Use the rule engine in the dashboard to route messages to databases, webhooks, or cloud services.

Example

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print(f'Connected with result code {rc}')
    client.subscribe('sensors/temperature')

def on_message(client, userdata, msg):
    print(f'{msg.topic}: {msg.payload.decode()}')

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect('localhost', 1883, 60)
client.loop_forever()

This subscribes to a temperature sensor topic. Any device publishing to sensors/temperature will have its messages printed.

Related on TokRepo

• Self-Hosted Solutions -- Self-hosted infrastructure platforms for IoT and beyond
• Monitoring Tools -- Tools for observing system health and device telemetry

Common pitfalls

• Default credentials on the dashboard are a security risk. Change the admin password immediately after deployment, especially in production.
• EMQX clustering requires proper network configuration. Nodes need to discover each other via DNS or static seeds, and firewalls must allow Erlang distribution ports.
• MQTT QoS 2 (exactly-once delivery) adds significant overhead. Use QoS 0 or 1 unless your application truly requires exactly-once semantics.