Discover Modbus Slaves

Scan unit IDs (slaves) on a known Modbus TCP host using a read-only FC3 probe. Subnet-wide host discovery stays in the Discovery panel.

When to use

• You know the PLC/gateway IP but not which unit IDs respond.
• Map multi-drop Modbus TCP gateways before wiring modbusTcp.request nodes.

Properties

Property	Type	Description
IP Address / Host	text	Required.
Port	number	Default 502.
Unit ID start	number	Default 1.
Unit ID end	number	Default 32 (max 247).
Timeout (ms)	number	Per-probe timeout. Default 2000.

Outputs

slaves[] with unitId, responseTimeMs, and exception flags. Dry Run returns an empty list.

See also

• Modbus TCP Request
• Test Modbus Connection
• Discovery