RabbitMQ STOMP and MQTT

RabbitMQ natively speaks AMQP, but many devices and applications use other messaging protocols. The STOMP and MQTT plugins extend RabbitMQ to support these additional protocols, making it a multi-protocol message broker that serves IoT devices, browser-based clients, and legacy systems alongside standard AMQP applications.

STOMP Protocol

STOMP stands for Simple Text Orientated Messaging Protocol. It is a simple, text-based protocol that works over TCP. Any language or platform that can open a TCP connection and read text can implement a STOMP client. STOMP clients connect to RabbitMQ and send/receive messages using plain text frames, making it easy to debug with raw tools like Telnet or Netcat.

Enabling STOMP

rabbitmq-plugins enable rabbitmq_stomp

STOMP listens on port 61613 by default.

STOMP Frame Structure

SEND
destination:/queue/my-queue
content-type:text/plain

Hello from STOMP client!
^@   (null byte terminates the frame)

A STOMP frame has a command (SEND, SUBSCRIBE, CONNECT), headers (key:value pairs), and a body. This simplicity is why STOMP is popular for scripting and rapid prototyping.

STOMP Destinations and RabbitMQ Mapping

STOMP Destination         Maps To
/queue/my-queue         → direct exchange, queue "my-queue"
/exchange/my-exchange   → named exchange "my-exchange"
/topic/my.routing.key   → amq.topic exchange, routing key "my.routing.key"
/temp-queue/xyz         → exclusive, auto-delete queue

WebSocket STOMP (rabbitmq_web_stomp)

The rabbitmq_web_stomp plugin wraps STOMP over WebSocket, allowing browser JavaScript to connect to RabbitMQ directly and receive real-time messages:

rabbitmq-plugins enable rabbitmq_web_stomp
# WebSocket STOMP listens on port 15674

In a browser:

const ws = new WebSocket('ws://localhost:15674/ws');
// Use a STOMP.js library over this WebSocket connection

MQTT Protocol

MQTT (Message Queuing Telemetry Transport) is a lightweight publish-subscribe protocol designed for constrained devices and low-bandwidth networks. It is the dominant protocol in IoT (Internet of Things) deployments. Smart home sensors, factory machines, GPS trackers, and remote weather stations all commonly use MQTT.

Why MQTT Is Different

Extremely small message overhead (2-byte minimum header)
Built-in Quality of Service (QoS) levels
Last Will and Testament — the broker publishes a message on behalf of a client that disconnects unexpectedly
Retained messages — the broker keeps the last message on a topic and delivers it to new subscribers immediately

Enabling MQTT

rabbitmq-plugins enable rabbitmq_mqtt

MQTT listens on port 1883 (plain TCP) and port 8883 (TLS).

MQTT QoS Levels

QoS 0 (At most once):
  Fire and forget. Message may be lost. Fastest.

QoS 1 (At least once):
  Message delivered at least once but may be duplicated.
  Consumer must handle duplicates.

QoS 2 (Exactly once):
  Message delivered exactly once. Safest but slowest.
  Four-step handshake between client and broker.

MQTT and RabbitMQ Routing

MQTT uses topic strings like sensor/building1/temperature. RabbitMQ maps these to AMQP routing via the amq.topic exchange. The MQTT topic separator / maps to the AMQP topic separator ..

MQTT topic:    sensor/building1/temperature
AMQP key:      sensor.building1.temperature

MQTT wildcard + (single level):  sensor/+/temperature
AMQP wildcard *:                 sensor.*.temperature

MQTT wildcard # (multi-level):   sensor/#
AMQP wildcard #:                 sensor.#

MQTT Configuration in rabbitmq.conf

mqtt.listeners.tcp.default = 1883
mqtt.allow_anonymous       = false
mqtt.vhost                 = /
mqtt.exchange              = amq.topic
mqtt.subscription_ttl      = 86400000  # 24 hours
mqtt.prefetch              = 10

WebSocket MQTT (rabbitmq_web_mqtt)

rabbitmq-plugins enable rabbitmq_web_mqtt
# WebSocket MQTT listens on port 15675

STOMP vs MQTT: Which to Use

Criterion              STOMP                MQTT
---------------------------------------------------
Target use case        Web/scripting        IoT devices
Protocol style         Text-based           Binary, compact
Browser support        Yes (web_stomp)      Yes (web_mqtt)
QoS levels             No (manual ack)      Yes (0, 1, 2)
Retained messages      No                   Yes
Last Will              No                   Yes
Overhead               Low                  Very low
Debugging ease         High (text frames)   Lower (binary)

Use MQTT for resource-constrained IoT devices, mobile apps, and any client where packet size matters. Use STOMP for web applications, scripting, and environments where simplicity and text-based debugging are priorities.

AMQP Clients Still Work

STOMP and MQTT clients publish messages that end up in the same RabbitMQ exchanges and queues as AMQP messages. A temperature reading from an MQTT sensor lands in a queue that an AMQP Java service can consume. A STOMP browser client can subscribe to events published by a Python AMQP producer. All protocols are first-class citizens in the same broker.

Summary

STOMP is a simple text-based protocol ideal for web clients, scripting, and any platform that can open a TCP socket. Enable it with rabbitmq_stomp on port 61613. MQTT is a lightweight binary protocol designed for IoT devices with QoS, retained messages, and Last Will support. Enable it with rabbitmq_mqtt on port 1883. Both protocols integrate with RabbitMQ's native AMQP routing through the amq.topic exchange. WebSocket variants (web_stomp, web_mqtt) enable browser-based real-time messaging.

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