Prologue

Prologue

OPyCua (IPA: /oʊ paɪ siː juː eɪ/) is an attempt to write an OPC UA communication stack using the Python programming language.

The Unified Architecture (UA) is THE next generation OPC standard that provides a cohesive, secure and reliable cross platform framework for access to real time and historical data and events.

~ OPC Foundation website

Some reading material

Read more about the OPC Unified Architecture over here:

• OPC Foundation website

  • About OPC Unified Architecture
    http://www.opcfoundation.org/Default.aspx/01_about/UA.asp

  • The OPC UA Licenses
    http://www.opcfoundation.org/Default.aspx/License/UALicense.asp

  • A list of existing OPC UA software ( Servers, Clients, SDK's, ... )
    http://www.opcfoundation.org/Default.aspx/OPCUAProducts.asp

  • The OPC Foundation memberlist
    http://www.opcfoundation.org/About/MemberList.aspx

  • OPC UA Downloads
    http://www.opcfoundation.org/Default.aspx/UASDK/Files/downloads.asp

• Other valuable resources

  • commsvr OPC UA eBook
    http://www.commsvr.com/UAModelDesigner/Index.aspx

  • OPC UA on Wikipedia
    http://en.wikipedia.org/wiki/OPC_Unified_Architecture

Goals

• 'share early, share often'
• Write a series of articles describing how opc ua works, using python code snippets.
• Create a consistent ua comunication stack in python for the binary TCP mapping.
• Create an API for writing OPC UA servers and clients.

Why python?

The Python Standard Library comes with all the tools we need to implement an OPC UA communication stack.

• There is socket to create TCP packets and throw them on the wire.
• There is ssl to create secure sockets. Using OpenSSL, which is also used by the OPC Foundation.
• There is struct to encode and decode binary data. ( But we'll probably use Construct )

Using these 3 modules we can implement the 'Transport Layer', the 'Secure Channel Layer' and the 'Serialization Layer'.