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WebSocket

Publishes processed events to web clients via WebSocket transport, ideal for real-time dashboards and applications

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Overview

The WebSocket Publisher Transport enables real-time event streaming to web clients, ideal for dashboards and interactive applications. Processed events are published as Json to subscribing client processes.

The example WebSocket client provided connects to a local WebSocket server (ws://localhost:7070/joule/ws/stream/quotes) and logs incoming event data to the browser console, allowing users to verify the streaming functionality.

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Client library: io.javalin:javalin:5.6.3arrow-up-right

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Examples & DSL attributes

This simple example leverages the default setting resulting in events published as StreamEvent JSON object to connected clients.

websocketPublisher:
  topic: quotes

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Example client

This HTML page acts as a WebSocket client to test data streaming from a Joule server.

Open it in Chrome, go to Developer Tools > Console, and click Start Streaming to view live event data streamed from ws://localhost:7070/joule/ws/stream/quotes.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>WebSocket Client</title>
</head>

<body>
    <button onclick="contactServer">Start Streaming</button>
</body>

<script>
    const socket = new WebSocket('ws://localhost:7070/joule/ws/stream/quotes');
    socket.addEventListener('open', function (event) {
        socket.send('Connection Established');
    });

    socket.addEventListener('message', function (event) {
        console.log(event.data);
    });

    const contactServer = () => {
        socket.send("Initialize");
    }
</script>
</html>

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Attributes schema

Attribute
Description
Data Type
Required

topic

User defined topic this stream relates too

String

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