WebSockets — Complete Guide
WebSockets — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of HTML Tutorial on Toolliyo Academy.
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HTML Tutorial · Lesson 55 of 100
WebSockets
Basics ✓ → Forms & semantics ✓ → APIs & performance → Projects
APIs & performance · 3 — HTML5, CSS/JS, security · ~10 min · HTML — HTML5 APIs & Advanced Features
What is this?
WebSockets open a persistent two-way channel between browser and server for live updates.
Why should you care?
MarkupVerse trading and chat widgets push prices without polling.
See it live — copy this example
Save as demo.html and open in your browser, or use Run Example below.
<section aria-live="polite">
<h2>Live FX — MarkupVerse Pay</h2>
<p>USD/INR: <strong id="rate">—</strong></p>
<p id="ws-status">Connecting…</p>
</section>
<script>
const ws = new WebSocket('wss://echo.websocket.events');
ws.onopen = () => { document.getElementById('ws-status').textContent = 'Connected'; ws.send('USDINR'); };
ws.onmessage = e => { document.getElementById('rate').textContent = e.data || '83.42'; };
ws.onclose = () => { document.getElementById('ws-status').textContent = 'Disconnected'; };
</script>
Run Example »
Edit the code below and click Run to see the result in Toolliyo’s live editor.
What happened?
- Use wss:// in production.
- Reconnect on close.
- Show connection state to users.
Practice next
- Open a WebSocket.
- Send a symbol on open.
- Update DOM on message.
- Add exponential backoff reconnect.
- Show last-updated timestamp.
Remember
Persistent socket. wss in prod. Handle reconnect.
MarkupVerse live rates
Pay page shows USD/INR tick updates.
Outcome: Rate changes without refresh.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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