ModbusTools are cross-platform (Windows, Linux) GUI simulators (client/server) that support TCP, UDP, RTU, ASCII, RTU/ASCII over TCP/UDP Modbus protocol types.

Cross platform GUI MODBUS TCP/RTU simulator & gateway. Interprets data types including ascii float and int.

Modbus simulator based on modbus-tk and kivy

Free Modbus Slave Simulator in the form of a standalone Windows app supporting Modbus RTU, TCP, UDP and ASCIIoverRTU protocols. The simulator does allow setting values before the connection is established as well as running multiple instances of the app at the same time. Also included are Linux and Mac OS X Mono versions.

Standalone Windows app supporting Modbus RTU, TCP, UDP, RTUoverTCP, RTUoverUDP, ASCIIoverRTU, ASCIIoverTCP and ASCIIoverUDP protocols. It is designed to allow running multiple instances of the app at the same time, just use a different port. Also included are Linux and Mac OS X Mono versions.

Modbus Process Simulator (early ModbusPal Enhanced, early Modbus Slave Simulator) is a Java MODBUS Protocol Slave Simulator.

Modbus simulator CLI is a high-performance modbus TCP server with customizable simulation. Available as CLI tool or as docker image

Cross-platform Modbus TCP simulator with GUI (Master & Slave) built in Python and PySide6.

Android tablet app for testing WiFi communication with Allen Bradley and/or Modbus programmable logic controllers (PLC) on a local network. Master to communicate with slave devices. This is using libplctag / jna libraries.

Standalone Windows application - Master for Allen Bradley, some Omron and Modbus PLCs. It is using libplctag library and C# Wrapper. Also included is the Mono version for Mac OS X (which should work fine in Windows as well as Linux Mono - see notes).

Modbus RTU/TCP test tool for Windows

Dead simple modbus simulator

A simple tool to simulate Modbus TCP and/or Modbus RTU slave