OPC UA / IEC 62541 Client and Server for Python >= 3.7 and pypy3 . http://freeopcua.github.io/, https://github.com/FreeOpcUa/opcua-asyncio
opcua-asyncio is an asyncio-based asynchronous OPC UA client and server based on python-opcua, removing support of python < 3.7. Asynchronous programming allows for simpler code (e.g. less need for locks) and potentially performance gains. This library has also sync wrapper over async API which may can be used in sync code instead of python-opcua
OPC UA binary protocol implementation is quite complete and has been tested against many different OPC UA stacks. API offers both a low level interface to send and receive all UA defined structures and high level classes allowing to write a server or a client in a few lines. It is easy to mix high level objects and low level UA calls in one application.
Most low level code is autogenerated from xml specification, thus adding missing functionality to client or server is often trivial.
coverage.py reports a test coverage of over 95 % of code, most of non-tested code is autogenerated code that is not used yet.
With pip
pip install asyncua
We assume that you already have some experience with Python, the asyncio module, the async / await syntax and the concept of asyncio Tasks.
The Client
class provides a high level API for connecting to APU UA servers, session management and access to basic
address space services.
The client can be used as a context manager. The client will automatically connect before the code inside the with
statement is executed. When your code leaves the with
statement the client will disconnect.
from asyncua import Client
async with Client(url='opc.tcp://localhost:4840/freeopcua/server/') as client:
while True:
# Do something with client
node = client.get_node('i=85')
value = await node.read_value()
Of course you can also call the connect
, disconnect
methods yourself if you do not want to use the context manager.
See the example folder and the code for more information on the client API.
The Node
class provides a high level API for management of nodes as well as data access services.
The Subscription
class provides a high level API for management of monitored items.
The Server
class provides a high level API for creation of OPC UA server instances.
The API remains mostly unchanged in regards to python-opcua. Main difference is that many methods have been refactored to return coroutines. Please have a look at the examples and/or the code.
The original documentation (for python-opcua) is available here ReadTheDocs.
A simple GUI client is available: https://github.com/FreeOpcUa/opcua-client-gui
Browse the examples: https://github.com/FreeOpcUa/opcua-asyncio/tree/master/examples
A good starting point are the minimal examples. Minimal client example: https://github.com/FreeOpcUa/opcua-asyncio/blob/master/examples/client-minimal.py Minimal server example: https://github.com/FreeOpcUa/opcua-asyncio/blob/master/examples/server-minimal.py
A set of command line tools also available: https://github.com/FreeOpcUa/opcua-asyncio/tree/master/tools
uadiscover
(find_servers, get_endpoints and find_servers_on_network calls)uals
(list children of a node)uahistoryread
uaread
(read attribute of a node)uawrite
(write attribute of a node)uacall
(call method of a node)uasubscribe
(subscribe to a node and print datachange events)uaclient
(connect to server and start python shell)uaserver
(starts a demo OPC UA server)
tools/uaserver --populate --certificate cert.pem --private_key pk.pem
How to generate certificate: https://github.com/FreeOpcUa/opcua-asyncio/tree/master/examples/generate_certificate.sh
What works:
- connection to server, opening channel, session
- browsing and reading attributes value
- getting nodes by path and nodeids
- creating subscriptions
- subscribing to items for data change
- subscribing to events
- adding nodes
- method call
- user and password
- history read
- login with certificate
- communication encryption
- removing nodes
Tested servers: freeopcua C++, freeopcua Python, prosys, kepware, beckhoff, winCC, B&R, …
Not implemented yet:
- localized text feature
- XML protocol
- UDP
- WebSocket
- maybe automatic reconnection...
What works:
- creating channel and sessions
- read/set attributes and browse
- getting nodes by path and nodeids
- autogenerate address space from spec
- adding nodes to address space
- datachange events
- events
- methods
- basic user implementation (one existing user called admin, which can be disabled, all others are read only)
- encryption
- certificate handling
- removing nodes
- history support for data change and events
- more high level solution to create custom structures
Tested clients: freeopcua C++, freeopcua Python, uaexpert, prosys, quickopc
Not yet implemented:
- UDP
- WebSocket
- session restore
- alarms
- XML protocol
- views
- localized text features
- better security model with users and password
Setting up the standard address-space from XML is the most time-consuming step of the startup process which may lead to long startup times on less powerful devices like a Raspberry Pi. By passing a path to a cache-file to the server constructor, a shelve holding the address space will be created during the first startup. All following startups will make use of the cache-file which leads to significantly better startup performance (~3.5 vs 125 seconds on a Raspberry Pi Model B).
Code follows PEP8 apart for line lengths which should be max 160 characters and OPC UA structures that keep camel case from XML definition.
All protocol code is under opcua directory
asyncua/ua
contains all UA structures from specification, most are autogeneratedasyncua/common
contains high level objects and methods used both in server and clientasyncua/client
contains client specific codeasyncua/server
contains server specific codeasyncua/utils
contains some utilities function and classesasyncua/tools
contains code for command lines toolsschemas
contains the XML and text files from specification and the python scripts used to autogenerate codetests
contains testsdocs
contains files to auto generate documentation from doc stringsexamples
contains many example filesexamples/sync
contains many example files using sync APItools
contains python scripts that can be used to run command line tools from repository without installing
pytest -v -s
pytest -v -s --cov asyncua --cov-report=html