# Introduction

EMQ X (Erlang/Enterprise/Elastic MQTT Broker) is an open source IoT MQTT message broker based on the Erlang/OTP platform.

Erlang/OTP is an excellent Soft-Realtime, Low-Latency and Distributed development platform.

MQTT is a lightweight message exchange protocol using publish-subscribe pattern.

EMQ X is designed for massive clients access and realizes fast and low-latency message routing between massive physical network devices:

  1. Stable to host large-scale MQTT client connections, and a single server node supports 2 million connections.
  2. Distributed cluster, fast and low-latency message routing, and single-cluster supports tens of thousands of routes.
  3. Extensible, support customized plugins, such as authentication and other functions.
  4. Comprehensive IoT protocol support, including MQTT, MQTT-SN, CoAP, LwM2M, and other TCP/UDP based proprietary protocol.

# Features List

  • Full MQTT V3.1/V3.1.1 and V5.0 protocol specification support
    • QoS0, QoS1, QoS2 message support
    • Persistent conversation and offline message support
    • Retained message support
    • Last Will message support
  • TCP/SSL connection support
  • MQTT/WebSocket/SSL support
  • HTTP message publishing interface support
  • $SYS/# system theme support
  • Client online status query and subscription support
  • Client ID or IP address authentication support
  • User name and password authentication support
  • LDAP authentication
  • Redis, MySQL, PostgreSQL, MongoDB, HTTP authentication integration
  • Browser cookie authentication
  • Access control (ACL) based on client ID, IP address, user name
  • Multi-server node cluster (Cluster)
  • Support manual, mcast, dns, etcd, k8s and other cluster discovery methods
  • Automatic network partition healing
  • Message rate limit
  • Connection rate limit
  • Configure nodes by partition
  • Multi-server node bridge (Bridge)
  • MQTT Broker bridge support
  • Stomp protocol support
  • MQTT-SN protocol support
  • CoAP protocol support
  • Stomp/SockJS support
  • Delay Publish ($delay/topic)
  • Flapping detection
  • Blacklist support
  • Shared subscription($share/<group>/topic)
  • TLS/PSK support
  • Rule engine
    • No action (debug)
    • Message republish
    • Bridge data to MQTT Broker
    • Check (debug)
    • Send data to web service