Modbus Master-Slave Communication
An accurate visualization of Modbus protocol communication & security vulnerabilities
Modbus is a serial communication protocol developed in 1979 for use with programmable logic controllers (PLCs). It has become a de facto standard in industrial communication and is now commonly used for connecting industrial electronic devices.
Network Architecture
Master (Client)
Initiates communication by sending requests to slaves
Slave (Server)
Responds to the master's requests by providing data or performing actions
Device Addressing
Each slave has a unique address (1-247)
Network Topology
Only one master can exist on a standard Modbus network
Interactive Modbus Communication Simulation
Experience real-time industrial communication protocols and security vulnerabilities
Configuration Panel
Network Topology
Real-Time Device Data
Slave 1
IdleSlave 2
IdleSlave 3
Idle📡 Communication Log
Modbus Frame Structure
Interactive visualization of Modbus RTU and TCP/IP frame structures with real-world examples
RTU Frame Format
RTU Protocol Benefits
The RTU (Remote Terminal Unit) frame uses a compact binary format optimized for serial communication. The CRC ensures data integrity across noisy industrial environments, making it ideal for RS-485 networks where reliability is critical.
TCP/IP Frame Format
TCP/IP Protocol Benefits
Modbus TCP/IP extends the protocol for Ethernet networks. It replaces CRC with TCP's built-in error detection and adds the MBAP header for transaction management, enabling multiple simultaneous connections and better scalability in modern industrial networks.
Example: Read Holding Registers (Function 03)
Request Frame
Response Frame
Request Analysis
This request asks slave device 01 to read 3 holding registers starting from address 107 (0x006B). Function code 03 specifically targets holding registers, commonly used for process values.
Response Analysis
The response contains 6 bytes of data (3 registers × 2 bytes each). Values: Register 1 = 555 (0x022B), Register 2 = 0 (0x0000), Register 3 = 100 (0x0064).