System ($SYS) Topics - Coreflux Documentation

Overview

The Coreflux MQTT Broker provides a comprehensive set of $SYS topics that enable you to monitor broker status, read configuration, track connections, and access LoT entity code. These topics follow the MQTT standard convention of using the $SYS prefix for broker-specific information.

Topics starting with $ are special topics in MQTT. They are not included when subscribing with wildcards like # at the root level. You must explicitly subscribe to them.

Why Use $SYS Topics?

When managing an MQTT broker in production, you need visibility into what’s happening inside. How many clients are connected? What version is running? What LoT entities are deployed? System topics give you this insight without external monitoring tools.

Think of $SYS topics as the broker’s dashboard in MQTT form. Instead of a web interface, you get live data streams—subscribe to them like any other topic and watch the broker’s vital signs in real-time.

Topic Hierarchy & Quick Reference

System topics in Coreflux follow a hierarchical structure:

$SYS/
├── Coreflux/
│   ├── Command                    # Send commands to broker
│   ├── Command/Output             # Receive command responses
│   ├── Config/New                 # Publish new configuration
│   ├── Version                    # Broker version info
│   ├── License                    # License information
│   ├── Resources/                 # Memory usage stats
│   ├── Config                     # Current configuration
│   ├── Config/Users               # User list
│   ├── Config/Rules               # Rules count
│   ├── Comms/
│   │   ├── Sessions               # Active sessions
│   │   ├── Clients                # Connected clients
│   │   └── Logins                 # Login events
│   ├── Actions/<name>             # Action LoT code
│   ├── Models/<name>              # Model LoT code
│   ├── Routes/<name>              # Route LoT code
│   └── Rules/<name>               # Rule LoT code
└── <OS>/                          # Platform-specific (e.g., Linux-x64, Windows-x64)
    ├── Python/Info                # Python integration status
    └── Comms/
        ├── TCP/Listeners          # Active TCP listeners
        ├── TCP/ActiveConnections  # TCP connections
        └── UDP/                    # UDP statistics

Read-Only Topics

Topic	Content
`$SYS/Coreflux/Version`	Broker version JSON
`$SYS/Coreflux/License`	License status
`$SYS/Coreflux/Config`	Current configuration
`$SYS/Coreflux/Config/Users`	User list (passwords masked)
`$SYS/Coreflux/Comms/Sessions`	Active sessions
`$SYS/Coreflux/Comms/Clients`	Connected clients
`$SYS/Coreflux/Actions/{name}`	Action LoT code
`$SYS/Coreflux/Models/{name}`	Model LoT code
`$SYS/Coreflux/Routes/{name}`	Route LoT code
`$SYS/Coreflux/Rules/{name}`	Rule LoT code

Writable Topics

Topic	Purpose
`$SYS/Coreflux/Command`	Send broker commands
`$SYS/Coreflux/Config/New`	Update configuration

In This Page

Section	Description
Command Topics	Send commands and receive responses
LoT Entity Topics	Access Actions, Models, Routes, and Rules code
Broker Information	Version, license, and resource usage
Configuration Topics	Current config, users, and rules
Connection Monitoring	Sessions, clients, and logins
Platform Topics	OS-specific communication and Python info

Command Topics

Send commands to the broker and receive responses through a publish/subscribe pattern.

Subscribe to output

Using any MQTT client (such as MQTT Explorer), subscribe to $SYS/Coreflux/Command/Output to receive responses

Publish command

Publish your command to $SYS/Coreflux/Command

Receive response

The broker publishes the result to the output topic

$SYS/Coreflux/Command

Publish command strings to this topic to control the broker. Topic: $SYS/Coreflux/Command Direction: Client → Broker Example: Use any MQTT client (such as MQTT Explorer) to publish to this topic. The message payload contains the command to execute:

Field	Value
Topic	`$SYS/Coreflux/Command`
Payload	`-addAction DEFINE ACTION Heartbeat ON EVERY 10 SECONDS DO PUBLISH TOPIC "system/heartbeat" WITH TIMESTAMP "UTC"`
Auth	Use `root` credentials

$SYS/Coreflux/Command/Output

Subscribe to receive responses from commands. Topic: $SYS/Coreflux/Command/Output Direction: Broker → Client Example responses:

Action 'Heartbeat' added successfully

Failed to add action: Syntax error at line 3

LoT Entity Topics

These topics contain the actual LoT code for each entity running in the broker.

Subscribe to these topics to retrieve the current LoT code for any Action, Model, Route, or Rule. This is useful for backup, debugging, or understanding what’s running in the broker.

$SYS/Coreflux/Actions/{ActionName}

Contains the LoT code for the specified action. Topic Pattern: $SYS/Coreflux/Actions/{ActionName} Payload: The complete LoT action definition Example: Subscribe to a specific action using MQTT Explorer or any MQTT client:

Field	Value
Topic	`$SYS/Coreflux/Actions/Heartbeat`

Payload received:

DEFINE ACTION Heartbeat
ON EVERY 10 SECONDS DO
    PUBLISH TOPIC "system/heartbeat" WITH TIMESTAMP "UTC"

$SYS/Coreflux/Models/{ModelName}

Contains the LoT code for the specified model. Topic Pattern: $SYS/Coreflux/Models/{ModelName}

$SYS/Coreflux/Routes/{RouteName}

Contains the LoT code for the specified route. Topic Pattern: $SYS/Coreflux/Routes/{RouteName}

$SYS/Coreflux/Rules/{RuleName}

Contains the LoT code for the specified rule. Topic Pattern: $SYS/Coreflux/Rules/{RuleName} Use your MQTT client to subscribe to these wildcard topics:

Entity Type	Topic Pattern
All Actions	`$SYS/Coreflux/Actions/#`
All Models	`$SYS/Coreflux/Models/#`
All Routes	`$SYS/Coreflux/Routes/#`
All Rules	`$SYS/Coreflux/Rules/#`

Broker Information

$SYS/Coreflux/Version

Broker version and build information. Topic: $SYS/Coreflux/Version Payload:

{
  "version": {
    "major": 0,
    "minor": 0,
    "patch": 0,
    "branch": "release",
    "os": "Linux-x64",
    "stage": "stable",
    "timestamp": "2025-09-12T16:41:00Z",
    "notes": "New Features:\n- Python integration for LoT\n"
  }
}

$SYS/Coreflux/License

License status and feature availability. Topic: $SYS/Coreflux/License Payload:

{
  "LicensedTo": "N/A",
  "IsActive": false,
  "Features": {
    "EnableLOTAdvancedFunctions": false,
    "EnableRouteAdvancedTiers": false,
    "EnableCluster": false
  }
}

$SYS/Coreflux/Resources

Memory usage statistics for the broker.

Topic	Description
`$SYS/Coreflux/Resources/MemoryInfoTotal`	Total available memory (bytes)
`$SYS/Coreflux/Resources/MemoryInfoUsage`	Current memory usage (bytes)

Configuration Topics

$SYS/Coreflux/Config

The current broker configuration as JSON. Topic: $SYS/Coreflux/Config Payload:

{
  "Name": "Coreflux DataHub",
  "Port": 1883,
  "TlsPort": 8883,
  "WebsocketPortTls": 443,
  "WebsocketPort": 5000,
  "FullDebugLog": false,
  "AnonymousLogin": true,
  "BindIPForMQTT": "0.0.0.0",
  "BindIPForMQTTwithTls": "0.0.0.0",
  "BindIpForWebSockets": "0.0.0.0",
  "BindIpForWebSocketsTls": "0.0.0.0",
  "ServerCertificatePath": null,
  "ServerCertificateKeyPath": null,
  "ServerCertificatePassword": null,
  "RootCACertificatePath": null,
  "ClientCertificateSourcePath": null,
  "ClientCertificationValidation": false,
  "ClientCertificateRevocationListPath": null,
  "CheckCertificateRevokationList": false,
  "CheckCertificateChainValidation": false,
  "ResendRetainTopics": false
}

To update the configuration, publish to $SYS/Coreflux/Config/New. See Broker Configuration for details.

$SYS/Coreflux/Config/Users

List of configured users (passwords are masked). Topic: $SYS/Coreflux/Config/Users Payload:

[
  {
    "UserName": "root",
    "Password": "********",
    "AllowedBaseTopic": "",
    "AllowedSystemConfiguration": true,
    "AllowedAssetManipulation": false,
    "AllowedUserManagement": false,
    "AllowedLogManagement": false
  }
]

User Permission Fields

Field	Description
`AllowedBaseTopic`	Base topic restriction for the user
`AllowedSystemConfiguration`	Can modify broker configuration
`AllowedAssetManipulation`	Can add/remove LoT entities
`AllowedUserManagement`	Can manage other users
`AllowedLogManagement`	Can access and manage logs

$SYS/Coreflux/Config/Rules

Information about configured rules. Topic: $SYS/Coreflux/Config/Rules

Connection Monitoring

$SYS/Coreflux/Comms/Sessions

Active MQTT sessions. Topic: $SYS/Coreflux/Comms/Sessions Payload:

[
  {
    "CreatedTimestamp": "2025-12-27T00:01:36.5008146Z",
    "DisconnectedTimestamp": null,
    "ExpiryInterval": 0,
    "Id": "mqtt-explorer-274f0040",
    "Items": {},
    "PendingApplicationMessagesCount": 0
  }
]

$SYS/Coreflux/Comms/Clients

Detailed information about connected clients. Topic: $SYS/Coreflux/Comms/Clients Payload:

[
  {
    "BytesReceived": 173,
    "BytesSent": 3943557,
    "ConnectedTimestamp": "2025-12-27T00:01:36.5008189Z",
    "Endpoint": "172.17.0.1:52256",
    "Id": "mqtt-explorer-274f0040",
    "LastNonKeepAlivePacketReceivedTimestamp": "2025-12-27T00:01:36.5168761Z",
    "LastPacketReceivedTimestamp": "2025-12-27T00:51:56.2986984Z",
    "LastPacketSentTimestamp": "2025-12-27T00:51:36.9346062Z",
    "ProtocolVersion": 4,
    "ReceivedApplicationMessagesCount": 16070,
    "ReceivedPacketsCount": 16124,
    "SentApplicationMessagesCount": 0,
    "SentPacketsCount": 53,
    "Session": {
      "CreatedTimestamp": "2025-12-27T00:01:36.5008146Z",
      "DisconnectedTimestamp": null,
      "ExpiryInterval": 0,
      "Id": "mqtt-explorer-274f0040",
      "Items": {},
      "PendingApplicationMessagesCount": 0
    }
  }
]

Client Fields

Field	Description
`BytesReceived`	Total bytes received from client
`BytesSent`	Total bytes sent to client
`ConnectedTimestamp`	When the client connected
`Endpoint`	Client IP and port
`Id`	Client ID
`ProtocolVersion`	MQTT protocol version (3=3.1, 4=3.1.1, 5=5.0)
`ReceivedApplicationMessagesCount`	Messages received
`SentApplicationMessagesCount`	Messages sent to client

$SYS/Coreflux/Comms/Logins

ClientId = lotvstudio-a6kjtbkwp, Endpoint = 172.17.0.1:53454, Username = root, Password = ******, CleanSession = True, ReasonCode = Success

Platform Topics

These topics are prefixed with the operating system identifier (e.g., Linux-x64, Windows-x64).

The OS prefix matches your broker’s platform. Check $SYS/Coreflux/Version to see the current OS identifier.

$SYS//Python/Info

Python integration status and available scripts. Topic: $SYS/Linux-x64/Python/Info (example for Linux) Payload:

{
  "Available": true,
  "Version": "3.11.2 (main, Apr 28 2025, 14:11:48) [GCC 12.2.0]",
  "Scripts": []
}

$SYS//Comms/TCP/Listeners

Active TCP listeners (ports the broker is listening on). Topic: $SYS/Linux-x64/Comms/TCP/Listeners Payload:

[
  {"Address": "0.0.0.0", "Port": "1883"},
  {"Address": "0.0.0.0", "Port": "80"},
  {"Address": "0.0.0.0", "Port": "443"},
  {"Address": "0.0.0.0", "Port": "5000"},
  {"Address": "::", "Port": "80"},
  {"Address": "::", "Port": "443"},
  {"Address": "::", "Port": "3000"}
]

$SYS//Comms/TCP/ActiveConnections

Currently active TCP connections. Topic: $SYS/Linux-x64/Comms/TCP/ActiveConnections Payload:

[
  {
    "State": "Established",
    "LocalEndPoint": "172.17.0.2:5000",
    "RemoteEndPoint": "172.17.0.1:52256"
  }
]

$SYS//Comms/UDP

UDP communication statistics. Topic: $SYS/Linux-x64/Comms/UDP

Access Control

By default, only authenticated users with appropriate permissions can access $SYS topics:

DEFINE RULE MonitoringAccess
    FOR USER "monitor-client"
    ALLOW SUBSCRIBE TO "$SYS/Coreflux/#"
    DENY PUBLISH TO "$SYS/Coreflux/Command"

Be careful when granting access to $SYS/Coreflux/Command. Users with publish access can execute administrative commands on the broker.

Quick Start

MQTT Broker

LoT Language

LoT Notebooks

Actions

Routes

Models

Rules

​Overview

​Why Use $SYS Topics?

​Topic Hierarchy & Quick Reference

​Read-Only Topics

​Writable Topics

​In This Page

​Command Topics

​$SYS/Coreflux/Command

​$SYS/Coreflux/Command/Output

​LoT Entity Topics

​$SYS/Coreflux/Actions/{ActionName}

​$SYS/Coreflux/Models/{ModelName}

​$SYS/Coreflux/Routes/{RouteName}

​$SYS/Coreflux/Rules/{RuleName}

​Subscribe to All Entities

​Broker Information

​$SYS/Coreflux/Version

​$SYS/Coreflux/License

​$SYS/Coreflux/Resources

​Configuration Topics

​$SYS/Coreflux/Config

​$SYS/Coreflux/Config/Users

​User Permission Fields

​$SYS/Coreflux/Config/Rules

​Connection Monitoring

​$SYS/Coreflux/Comms/Sessions

​$SYS/Coreflux/Comms/Clients

​Client Fields

​$SYS/Coreflux/Comms/Logins

​Platform Topics

​$SYS//Python/Info

​$SYS//Comms/TCP/Listeners

​$SYS//Comms/TCP/ActiveConnections

​$SYS//Comms/UDP

​Access Control

​Next Steps

Broker Configuration

Broker Commands

Overview

Why Use $SYS Topics?

Topic Hierarchy & Quick Reference

Read-Only Topics

Writable Topics

In This Page

Command Topics

$SYS/Coreflux/Command

$SYS/Coreflux/Command/Output

LoT Entity Topics

$SYS/Coreflux/Actions/{ActionName}

$SYS/Coreflux/Models/{ModelName}

$SYS/Coreflux/Routes/{RouteName}

$SYS/Coreflux/Rules/{RuleName}

Subscribe to All Entities

Broker Information

$SYS/Coreflux/Version

$SYS/Coreflux/License

$SYS/Coreflux/Resources

Configuration Topics

$SYS/Coreflux/Config

$SYS/Coreflux/Config/Users

User Permission Fields

$SYS/Coreflux/Config/Rules

Connection Monitoring

$SYS/Coreflux/Comms/Sessions

$SYS/Coreflux/Comms/Clients

Client Fields

$SYS/Coreflux/Comms/Logins

Platform Topics

$SYS//Python/Info

$SYS//Comms/TCP/Listeners

$SYS//Comms/TCP/ActiveConnections

$SYS//Comms/UDP

Access Control

Next Steps