What is Modbus protocol ?

    Modbus is a communication protocol developed by MODICON Inc. in 1979. It's a standard, truly open and the most widely used network communication protocol in industrial automation field. SCADA and HMI software can easily integrate serial devices together via Modbus protocol.

What is Modbus/TCP protocol ?

    Modbus/TCP protocol is a variant of Modbus protocol. It was developed in 1999 to allow Internet community access Ethernet devices.

What software supports Modbus and Modbus/TCP protocol ?

    Most of SCADA ( Supervisor Control And Data Acquisition ) and HMI software support Modbus. For example:
Citect, ICONICS, iFIX, InduSoft, Intouch, Entivity Studio, Entivity Live, Entivity VLC, Trace Mode, Wizcon, Wonderware... etc

What are the benefits of using Modbus and Modbus/TCP protocol ?

    1. Openness, no license fees.
    2. Widely supported by SCADA and HMI software
    3. Easy to use
    4. Easily integrate variant devices
    5. Low development cost
    6. Widely knowledge resource

Modbus Resource ?

http://www.modicon.com
Web page of original Modbus protocol inventor, MODICON Inc.

http://www.modbus.org
A community for Modbus users of Modbus users

http://www.modbustools.com
ActiveX component and test tools to communicate with equipments via Modbus (RTU/ASCII) or Modbus/TCP