What is the standard port number for Modbus TCP?

The standard port number for Modbus TCP is 502. Modbus TCP is a widely-used communication protocol for industrial automation and control systems, operating over TCP/IP networks. Each application and service typically uses a specific port number, which helps network devices correctly route the traffic.

Port 502 is designated specifically for Modbus TCP, allowing devices such as Programmable Logic Controllers (PLCs) and other industrial equipment to communicate seamlessly and accurately. This designation is part of the Internet Assigned Numbers Authority (IANA) service name and transport protocol port number registry, which standardizes these essential communication protocols across various devices and systems.

Knowing this port number helps security professionals implement appropriate security measures, like firewalls and intrusion detection systems, to protect the integrity and availability of industrial control systems using Modbus TCP. Additionally, since Modbus can operate both on serial connections and over TCP/IP, understanding the specific port used for TCP communication is vital for network configuration and troubleshooting.