ModbusLab

Windows desktop software · Current version 1.0.0

Modbus RTU-to-SNMP gateway

Poll points from Modbus RTU devices, keep their latest values and expose a configured OID map to an SNMP manager.

Read the gateway setup guide · Check installer availability and Windows requirements

Modbus sources

The gateway can read the simulator's internal device model for a one-computer lab test, or use a selected serial port to poll a physical Modbus RTU bus. The physical source needs matching serial settings and an available COM port. Do not run another master on the same half-duplex bus at the same time.

Point mapping

Each enabled mapping selects a unit ID, a Modbus data area and PDU address, an SNMP OID suffix, an access mode and a poll interval. Supported point representations include Boolean, unsigned 16-bit, signed 16-bit and 32-bit floating point. Byte and word swapping, scaling, offset and consecutive-error limits are configurable. The application generates a MIB from the configured map.

The polling client reads coils, discrete inputs, input registers and holding registers with function codes 01-04. SNMP v1 and v2c requests supported by the agent include GET, GETNEXT, GETBULK and SET. A writable coil or holding-register mapping translates SNMP SET requests to Modbus writes using function code 05, 06 or 16.

SNMP versions and network scope

The implemented agent supports community-based SNMP v1 and v2c. It does not implement SNMPv3. SNMP community strings are not encrypted by v1/v2c; the default local preset binds to 127.0.0.1:1161 and uses public for reads and private for writes. Keep the bind address on loopback for a local test. Do not expose the agent to an untrusted network.

Scope

  • The gateway is software within the ModbusLab Windows desktop app, not a separate hardware appliance.
  • Its Modbus source is RTU over a serial connection or the internal simulator. It does not provide Modbus TCP transport.
  • Do not use the example enterprise number 99999 in a distributed MIB. Configure an enterprise number assigned to your organization.
  • Application version metadata is 1.0.0. The website does not currently have a public installer link; see the download status.

References