MQTT 5.0

MQTT 5.0 implementation with enhanced flow control, properties, and session handling.

Additional Features

• Reason Codes & User Properties
• Shared Subscriptions
• Topic Aliases
• Message Expiry
• Server Keep Alive (server-enforced)
• Receive Maximum (client/server)
• Enhanced Session Expiry

Quick Start

protocols:
  mqtt:
    version: "5.0"
    port: 1883

---

Configuration (5.0)

Fields below map to MqttConfigDTO and MqttV5ConfigDTO.

Field	Type	Default	Description
maximumSessionExpiry	long (s)	86400	Max session expiry the server will accept from clients.
maximumBufferSize	long (bytes)	10485760	Max per-connection buffer before backpressure.
serverReceiveMaximum	int	10	Server’s Receive Maximum (limits in-flight QoS>0 publishes to the server).
clientReceiveMaximum	int	65535	Maximum Receive Maximum advertised to clients (limits in-flight QoS>0 publishes to the client).
clientMaximumTopicAlias	int	32767	Max topic aliases a client may use (client→server).
serverMaximumTopicAlias	int	0	Max topic aliases the server will use (server→client).
strictClientId	boolean	false	Enforce strict client ID validation.
minServerKeepAlive	int (s)	0	Minimum server keep-alive interval enforced on clients.
maxServerKeepAlive	int (s)	60	Maximum server keep-alive interval enforced on clients.

Example with flow-control & aliases

protocols:
  mqtt:
    version: "5.0"
    port: 1883
    maximumBufferSize: 2097152       # 2 MiB
    maximumSessionExpiry: 604800     # 7 days
    serverReceiveMaximum: 50
    clientReceiveMaximum: 1000
    clientMaximumTopicAlias: 256
    serverMaximumTopicAlias: 32
    minServerKeepAlive: 10
    maxServerKeepAlive: 120
    strictClientId: true

Shared Subscriptions

MAPS fully supports shared subscriptions as defined in the MQTT 5 specification (§4.8).
This allows multiple clients in the same subscription group to share the load of receiving messages from a topic.

• Syntax:

  $share/{group}/{topic}

• {group} is the name of the subscription group.
• {topic} is the normal MQTT topic filter.

Example

If two clients subscribe to:

$share/analytics/sensors/temperature

then MAPS will balance delivery across the clients in the analytics group — each message is delivered to only one client in the group, rather than broadcasting to all subscribers.

This is useful for load-balancing consumers (e.g., analytics workers, stream processors).

Diagram

---