CAS Modbus Scanner - A free tool for communicating with Modbus devices
List of Modbus Monitoring Software - DEV Community
ModRSsim2 Modbus Slave/Server RTU/TCP and DF1 Simulator | Support of ACE AUTOMATION Europe
Modbus Test Utility - Free alternative to Modscan / Modbus Poll / Simply Modbus - Software and Tools - Industrial Automation, PLC Programming, scada & Pid Control System