OPC UA data packet format

Question

As OPC UA works on top of TCP/IP, so the data packets format would be the same as that of TCP/IP or it will have different? I am interested in studying the data packets of OPC UA and its format and compare with MQTT data packets. If somebody has information about both, kindly share. Also the Overhead added to the data packet by OPC UA/MQTT to the original data.

Answer 1

You should see part 6 of the IEC 62541 series (publ. 2015), it deals with the concrete mapping of

• abstract services (part 4),
• data structures (part 5) and
• the security model (part 2)

to 'physical' protocols and contains all information you need.

Section 5 contains the data encoding for OPC UA binary (5.2) and XML (5.3). Section 6 describes the implementation of security protocols and section 7 contains the mappings to concrete transport protocols:

• sect. 7.1: OPC UA TCP
• sect. 7.2: SOAP/HTTP
• sect. 7.3: HTTPS