Port 502: Modbus
Port 502 is Modbus, a simple industrial protocol from the 1970s that is still the most common way PLCs and other factory-floor equipment talk to each other. It has no built-in security, which is a well-known concern in operational technology networks.
| Port number | 502 |
|---|---|
| Service | Modbus Protocol |
| Protocol | TCP |
| Category | IoT & automation |
| Default encryption | No |
Frequently asked questions
What is port 502 used for?
Port 502 is Modbus, a simple industrial protocol from the 1970s that is still the most common way PLCs and other factory-floor equipment talk to each other. It has no built-in security, which is a well-known concern in operational technology networks.
Is port 502 TCP or UDP?
Port 502 (Modbus) uses TCP.
Is port 502 secure?
Port 502 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 502 on my firewall?
Only if you specifically need Modbus. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.