The Short Answer
If your PLC is more than 5 years old — Modbus TCP. If you are deploying new Siemens, B&R, or Beckhoff equipment — OPC-UA. If you have both — use an OPC-UA gateway that speaks Modbus on one side and OPC-UA on the other.
Modbus TCP: Simple, Universal, Fast
Modbus TCP is a 40-year-old protocol that every industrial device supports. It is simple: you read and write registers by address. No security, no data types beyond registers, no browsing capability. Perfect for reading sensor values from legacy PLCs and simple I/O devices.
OPC-UA: Rich, Secure, Modern
OPC-UA carries data types, metadata, security certificates, and a browsable address space. Your software can discover what variables a PLC exposes without pre-configuring register addresses. Built-in encryption and authentication make it safe for cloud connectivity.
Our Recommendation for Indian Factories
Most factories we work with have a mix of legacy and new equipment. We deploy an OPC-UA server that reads Modbus from old devices and exposes everything through a unified OPC-UA interface to the cloud.
Do not pick one protocol — pick a gateway architecture that speaks both. Standardise your cloud layer on OPC-UA and let the gateway handle legacy Modbus devices.
Need Help With This?
Have a mix of old and new PLCs? We design protocol gateway architectures for Indian factories.
Talk to Our Team →