Modbus
Use Modbus TCP to integrate Gateway Pro sensor data with third‑party automation and control systems.
Modbus TCP protocol basics
Gateway Pro uses Modbus TCP (Modbus over TCP/IP).
Key protocol points:
Transport: TCP.
Default port:
502.Client/server roles: the data consumer is commonly called the client (or master). The device serving data is the server (or slave).
Data model: values are exposed through addressable objects (commonly called coils and registers). A register map defines which values are available and where.
Unit ID: a device identifier included in Modbus TCP frames. It is mainly used for routing through TCP-to-serial gateways. Many Modbus clients still require it to be set and to match the server configuration.
Modbus address notation varies by tool.
Some clients show 0-based register offsets. Others show 1-based addresses (for example, “4xxxx” holding registers).
Prerequisites
You have an Aranet Cloud account.
Your Gateway Pro is connected to Aranet Cloud. See Connecting to Aranet Cloud.
Use the latest Gateway Pro firmware. See Updating the Firmware.
Enable Modbus integration
On Gateway Pro, open Settings.
Press Integrations.
Verify that the Gateway Pro is connected to Aranet Cloud.
If the Gateway Pro is not connected, you’ll see the following screen:
Press Connect to Aranet Cloud. Scan the QR code to add the Gateway Pro to a workspace.
You can also connect from Aranet Cloud directly: https://help.aranet.com/aranet-cloud-page/aranet-cloud-landing-page/gateway-management/connect-gateway
In Aranet Cloud:
Open the Gateway Pro.
Click MANAGE.
Open Integration configuration.
Select MODBUS and enable it.
Configure the required fields:
Port (default:
502)Unit ID (must match the Unit ID used by your Modbus client/master)
JSON file: the register layout definition. This file defines how Gateway Pro data is mapped to Modbus addresses. Aranet Cloud provides an auto-generated default register layout file that you can download and review.
Click Save.
Close the Cloud management tab when you’re done.
The Gateway Pro UI may be unresponsive while the remote management session is open.
Integration status
The Gateway Pro Dashboard shows an integration icon. Icon color indicates the current status.
Green means Modbus is active and healthy.
Yellow means Modbus is active, but there is a warning. Press the integration icon to view details.
Red means Modbus has an error and is unavailable. Press the integration icon to view details.
Status messages
Green icon + status text Active:
All statuses with _INFO_ except _INFO_DISABLED_BY_USER.
MODBUS_INFO_NO_ERR
Yellow icon + status text Warning:
All statuses with _WARNING_.
MODBUS_WARNING_MAP_ADDR_COLLISION
MODBUS_WARNING_MAP_OFFSET_INVALID
Red icon + status text Error:
All statuses with _ERROR_ except _ERROR_DISABLED_BY_LICENCE.
MODBUS_ERROR_CONTEXT_NULL
MODBUS_ERROR_CONTEXT_FAILED
MODBUS_ERROR_MAP_ALLOC_FAILED
MODBUS_ERROR_MAP_JSON_FAILED
MODBUS_ERROR_MAP_OFFSET_MISSING
MODBUS_ERROR_SETTINGS_CONFIG_FAILED
MODBUS_ERROR_SETTINGS_JSON_EMPTY
MODBUS_ERROR_SETTINGS_WRONG_PORT
MODBUS_ERROR_SETTINGS_WRONG_UNIT_ID
MODBUS_ERROR_LISTEN_FAILED
MODBUS_ERROR_UNKNOWN_ERROR
Red icon + status text Expired:
MODBUS_ERROR_DISABLED_BY_LICENCE
You can also see the status in Aranet Cloud:
Modbus details shown on Gateway Pro
On the Gateway Pro display, Modbus details include:
Status (message): current Modbus integration state.
Updated: timestamp of the last status refresh.
Port: configured Modbus TCP port.
Unit ID: configured Unit ID.
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