IEC 104 Connector

What Is It?

The IEC 104 Connector makes your IoT sensor data available to industrial control systems (SCADA). It acts as a server that SCADA clients can connect to in order to read real-time process data — such as temperatures, voltages, or switch states — using the widely adopted IEC 60870-5-104 standard.

In short: the IEC 104 Connector is the outbound gateway that delivers your data to control rooms and monitoring systems.

How It Works

1. The connector reads data points from the central data store.
2. It listens for incoming connections from SCADA clients on a configurable TCP port.
3. When a client connects, it can request all current data points or receive live updates as values change.

IoT Sensors → MQTT → Data Store → IEC 104 Connector → SCADA Client

The connector continuously monitors the data store for changes and pushes updates to all connected clients automatically.

Connection Details

Setting	Default
Protocol	TCP/IP
Port	2404
Port Range	2404–2420
Mode	Server (clients connect to it)
Max Clients	Up to 100 simultaneous connections

The connector only operates as a server. It does not connect to other IEC 104 systems as a client.

IEC 104 Addressing

Every data point in the IEC 104 protocol is identified by two addresses:

Address	What It Means	Range
CASDU	Station address — identifies a group or location	0–65,535
IOA	Data point address — identifies a specific measurement	0–16,777,215

The combination of CASDU and IOA must be unique across the system. Think of CASDU as the "building" and IOA as the "sensor" within that building.

Example:

• CASDU 150, IOA 100 → Temperature in Transformer Room 1
• CASDU 150, IOA 101 → Pump Status in Transformer Room 1
• CASDU 200, IOA 100 → Temperature in Transformer Room 2

Supported Data Types

The connector supports the following IEC 104 data types:

Monitoring types (inbound data):

Type	Name	Used For	Examples
Type 1	Single Point	On/off states	Door open/closed, alarm active/inactive
Type 3	Double Point	Two-bit states	Breaker open/closed/transit/invalid
Type 13	Measured Normalized	Normalized measurements	Proportional values, percentages
Type 30	Single Point with Timestamp	On/off states with time	Switch state changes with exact time
Type 31	Double Point with Timestamp	Two-bit states with time	Breaker state changes with exact time
Type 32	Step Position with Timestamp	Transformer tap positions	-64 to 63
Type 36	Float with Timestamp	Measurements	Temperature, voltage, current, humidity

Command types (outbound control):

Type	Name	Used For	Examples
Type 45	Single Command	On/off commands	true/false
Type 46	Double Command	Open/close/stop commands	0–3 (not permitted, off, on, not permitted)
Type 47	Regulating Step Command	Step up/down commands	0–3 (not permitted, lower, higher, not permitted)
Type 50	Set-point Normalized	Analog set-point values	Floating-point set-points

Recommendation: Use Type 36 for analog measurements and Type 30 for binary states. Both include a timestamp for traceability.

Configuration

The connector is configured in two ways:

1. Management UI / API — The primary method. When you create an IEC 104 connector in the Management UI, the configuration (network settings, protocol parameters, linked mappings) is stored in the database and automatically pushed to the connector via the data store.
2. Command-line / TOML file — For initial startup parameters (connector ID, data store connection, log level). A TOML configuration file can be generated with the config-gen subcommand.

Startup Parameters

These parameters are passed via command line or TOML file when starting the connector:

Parameter	Description	Required	Default
--id	Unique connector ID (from the Management UI)	Yes	—
--log-level	Log verbosity (trace, debug, info, warning, error, critical, off)	No	info
--config	Path to a TOML configuration file	No	—

Redis subcommand — Connection to the data store:

Parameter	Description	Default
--host	Data store host (with optional port, e.g., datastore:6379)	127.0.0.1
--port	Data store port (overrides port in --host)	6379
--pwd	Data store password	—

Managed Settings (via Management UI)

The following settings are configured through the Management UI and pushed to the connector automatically. You do not need to set them manually.

Network Settings:

Setting	Description	Default
Host	Which network interface to listen on (0.0.0.0 = all)	0.0.0.0
Port	TCP port the server listens on	2404
Max Connections	Maximum number of simultaneous client connections	1

Protocol Timing Parameters:

Setting	Description	Default
T1	Timeout for sent messages awaiting acknowledgment	15 seconds
T2	Timeout for sending an acknowledgment	10 seconds
T3	Idle timeout before a test message is sent	20 seconds
K	Maximum number of unacknowledged messages	12
W	Number of received messages before an acknowledgment is sent	8

In most cases, the default timing parameters do not need to be changed. Only adjust them if your SCADA system vendor recommends specific values.

Dynamic Configuration Updates

When you change a connector's settings or linked mappings in the Management UI, the backend pushes the updated configuration to the data store. The connector detects the change and automatically restarts its services with the new configuration — no manual restart required.

Configuration Error Handling

The connector includes robust error handling for configuration issues:

• Invalid configuration — If the connector receives an invalid configuration from the data store, it logs a detailed error message and continues running with the previous valid configuration.
• Partial failures — Network interruptions or malformed data are handled gracefully without crashing the connector.
• Recovery — Once a valid configuration is published, the connector automatically picks it up and reconfigures itself.

Check the connector logs for specific error details when troubleshooting configuration issues.

Data Store Integration

The connector reads data points from the central data store. The backend publishes connector configuration and mapping data to the data store under:

connectors:{CONNECTOR_ID}:config     — connector settings (including stream configuration)
connectors:{CONNECTOR_ID}:mapping    — linked mapping definitions

The connector's data streams (input, output, error) are configured via the Management UI and included in the published configuration. The input stream is used to receive data point updates from other connectors.

Process image data points are stored under:

process:image:casdu:{CASDU}:ioa:{IOA}

When a value changes in the data store, the connector automatically pushes the update to all connected SCADA clients.

Client Interaction

Initial Data Request

When a SCADA client connects and sends a "General Interrogation" request, the connector responds with all current data points. This gives the client a complete snapshot of the current system state.

Live Updates

After the initial data dump, the connector sends updates whenever new data is written to the data store. Each update is forwarded to all connected SCADA clients immediately.

Cause of Transmission (CoT)

The connector forwards the Cause of Transmission (CoT) from the original data point. For example, if a data point was written with CoT "spontaneous", that same CoT is sent to the SCADA client. This preserves the semantic meaning of each update through the entire data pipeline.

Connection Monitoring

The connector and connected clients exchange periodic test messages to verify the connection is still alive. If a client disconnects, its session is cleaned up automatically.

Tested Compatibility

The IEC 104 Connector has been tested with the following SCADA systems and devices:

• Siemens RTU A8000 (ETI4)
• Vivavis HIGHLEIT
• PSIcontrol

Connector Health Reporting

The connector publishes its operational state to the central data store, enabling the Management UI to display real-time health information:

State	Meaning
Starting	The connector is initializing and loading configuration
Running	The connector is connected and processing data normally
Error	Configuration loading failed or a critical error occurred
Stopped	The connector is shutting down gracefully

The connector also reports its software version at startup, which is visible in the Management UI.

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