Device Simulator

The Device Simulator runs the current Device Agent before hardware is ready. It starts a browser device from the DeviceSpec, connects to MQTT, reports state, responds to commands, and verifies device lists, status, events, and message flow.

Validate the Device Flow

The simulator is useful when you need to:

• Confirm that commands, telemetry, and events match expectations after creating a Device Agent.
• Validate conversation control and status display before a hardware prototype is ready.
• Check field names, command parameters, and event definitions before SDK or MQTT access work starts.
• Demo or debug with a device that can come online immediately and respond to commands.

The simulator does not read real sensors, control actuators, or validate firmware, drivers, network behavior, or system permissions. It is for validating the Device Agent and DeviceSpec; production still requires a real device integration.

Start a Simulated Device

In the Device Agent workspace, click Try a simulated device in the Devices panel. The dialog shows the simulated device details:

• Device name: generated from the current Device Agent name.
• Device ID: a generated ID with a sim- prefix. You can regenerate it.
• Connection details: expand the section to view namespace, MQTT broker, username, and password status.

Click Connect. The browser starts the simulated device, connects it to MQTT, and reports the first status and state to the current Device Agent.

After it connects, the device list shows a device with the Sim badge. Select it to open the status panel, where you can inspect:

• Device online status.
• Current state.
• Available commands.
• Recent events.

State Reports

The simulator builds the initial state from telemetry fields in the DeviceSpec. If a field has a default value, the simulator uses it. Otherwise it generates a basic value by field type: false for booleans, 0 for numbers, {} for objects, [] for arrays, and an empty string for strings.

After connection, the simulated device keeps the MQTT connection open and regularly reports the current state. The status panel updates as new reports arrive.

If the DeviceSpec includes online or connected, the simulator sets those fields to true when connected and false when disconnected.

Conversation Control

Keep the simulated device selected, then enter a control request in the conversation area:

Set the target temperature to 24 degrees and switch to auto mode.

The Device Agent selects commands from the DeviceSpec and prepares parameters. The simulated device validates the command name and parameters against the DeviceSpec. If validation passes, it updates local state and reports the latest state again.

Use these signals to confirm that the command worked:

• Current state changed.
• The command is listed under available commands.
• The conversation shows a command result.

If the command name does not exist, required parameters are missing, or parameter types do not match, the simulator returns a failed result. In that case, adjust the command name, parameter fields, or field types in the DeviceSpec.

Simulate Events

If the DeviceSpec defines events, you can ask the simulated device to report one:

Have the current simulated device report an over-temperature event.

The Device Agent generates an event message that matches the current event definition. After it is reported, check Recent events in the status panel.

Events do not automatically update current state. If the state should also change, ask the simulated device to report a new state snapshot as well.

Disconnect and Reconnect

The simulated device runs in the current browser. If you close the page, refresh the page, or disconnect it, it goes offline. The device list may still keep the simulated device record, so you can review its last state or delete it and start a new simulated device.

Usually, one browser simulated device is enough for a Device Agent. To use a different device ID, delete the old simulated device and create a new one.

Move to a Real Device

Item	Simulated device	Real device
Runs in	Current browser	Device firmware, gateway, or backend service
State source	Generated from the DeviceSpec and command results	Real sensors, actuators, or business systems
Command behavior	Updates simulated state and returns a result	Controls real hardware or services
Best for	PoC, demos, and DeviceSpec debugging	Real integration, hardware testing, and production

Next Steps

• Read Use a Device Agent to select a simulated device and control it through conversation.
• Read SDK Access to connect the same DeviceSpec to real hardware.
• Read MQTT Access for the topics and payloads shared by simulated and real devices.