OPC UA communication
9.1 What you need to know about OPC UA
Communication
Function Manual, 11/2019, A5E03735815-AH
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Independence of a specific transport layer
OPC UA currently supports the following transport mechanisms and protocols:
● The transfer of messages as a binary stream directly via TCP/IP
● The transfer of messages with XML via TCP/IP and HTTP. This transport mechanism
allows only a slow transfer and is therefore almost never used. S7-1500 CPUs do not
support this transport mechanism.
Binary data exchange is supported by all OPC UA applications (required in OPC UA
specification).
Simple client-server principle
An OPC UA server provides a great deal of information within a network, e.g. relating to the
CPU, the OPC UA server itself, the data and the data types. An OPC UA client accesses this
information.
Implementation in different programming languages
The OPC Foundation has implemented the OPC UA standard in several programming
languages: Stacks for .NET, ANSI C and Java are available, although maintenance has
been discontinued for the stacks for ANSI C and Java.
The OPC Foundation offers the .NET stack as well as example programs as open source
software. See Github (https://github.com/opcfoundation
).
A number of companies offer Software Development Kits (SDK). These development
packages contain the stacks of the OPC Foundation and other functionalities that facilitate
the development of solutions.
Advantages of using SDKs:
● Support from the supplier
● Tested software
● Detailed documentation
● Clear license conditions (important for selling of solutions)
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