You can use this to push data from a "OPC UA Subscription" over a WebSocket to the Browser/WebSocket-Client
"opcua-sub-to-websocket" can support multiple WebSocket-Clients and pushes all received subscription-notifications to all WebSocket-Clients.
Startup on Localhost:
Console1: python server.py
Console2: python client.py
Console3: python ws_client.py
And as many Browser instances of test.html as you want!
Provided is a sample "OPC UA Server" which generates random events and datachanges!
The timing can be adjusted in server.py:
async def random_updater(random_node):
while True:
await asyncio.sleep(random.randint(1,10)/10) #<-------------
random_node.set_value(ua.DataValue(ua.Variant(random.randint(70,90), ua.VariantType.UInt64)))
print(datetime.now(), "datachange")
async def event_gen(myevgen):
count = 0
while 1:
await asyncio.sleep(random.randint(1,10)/10) #<-------------
myevgen.event.Message = ua.LocalizedText("MyFirstEvent %d" % count)
myevgen.event.Severity = count
myevgen.event.MyNumericProperty = count
myevgen.event.MyStringProperty = "Property " + str(count)
myevgen.trigger()
count += 1
print(datetime.now(), "event")also provided is a test HTML-Page with some basic JavaScript to connect/reconnect to WebSockets:
<!DOCTYPE html>
<html lang="de">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Andreas Heine</title>
</head>
<body>
<div id="content"> </div>
<script>
var content = {}
let data
function connect() {
let url = "ws://127.0.0.1:8000";
let s = new WebSocket(url);
s.onopen = function(event) {
console.log(event);
}
s.onclose = function(event) {
console.log(event);
setTimeout(function() {
connect();
}, 2000);
}
s.onerror = function(event) {
console.log(event);
}
s.onmessage = function(event){
data = JSON.parse(event.data);
//console.log(data);
if (data.topic == "datachange notification"){
content[data.payload.node] = {
value: data.payload.value,
data: data.payload.data,
};
}
if (data.topic == "event notification"){
content["Event"] = data;
}
if (data.topic == "status change notification"){
content["Status"] = data;
}
document.getElementById("content").innerHTML = JSON.stringify(content);
}
}
connect();
</script>
</body>
</html>aswell as an python based WebSocket Client :
import asyncio, websockets
async def request():
uri = "ws://127.0.0.1:8000"
async with websockets.connect(uri) as websocket:
while 1:
msg = await websocket.recv()
print(msg)
asyncio.get_event_loop().run_until_complete(request())Interested? Contact me: info@andreas-heine.net