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Japanese Yen Price API websocket setup for live price feeds

Japanese Yen Price API websocket setup for live price feeds

Japanese Yen Price API websocket setup for live price feeds

You need a live Japanese yen (JPY) price feed you can push to browsers and mobile clients over WebSocket without babysitting infrastructure. By the end of this guide, you’ll have a thin service that polls Indices-API for the latest USD-quoted price, relays it to clients via WebSocket, and a repeatable way to backfill a recent series for charts and P&L baselines.

What we’re building: a JPY live feed bridged from Latest to WebSocket

Indices-API is a JSON REST service. We’ll poll its Latest endpoint on a cadence aligned with the API’s update frequency, then fan out updates to subscribed clients over a lightweight WebSocket. This approach gives you “live-enough” prices with predictable costs and simple ops.

Illustration: Japanese Yen Price API websocket setup for live price feeds

Two moving parts:

  • A backend worker that calls the Latest endpoint, parses the JPY price from the response map, and publishes to a WebSocket channel.
  • A short backfill function that pulls recent daily values for chart initialization and last-close comparisons before the first live tick arrives.

Before you write code, make sure you have an API key. You can get one in minutes: Register. Pricing notes are on the site (there’s a PRO $49.99/mo tier with a 7‑day trial).

Confirm the symbol for Japanese yen (use the Symbols page)

Indices-API data objects use symbolic codes for everything you query or parse. Do not guess the JPY code. Confirm it on the Symbols page. You’ll also find whether the response map includes a direct key for JPY or a USD-prefixed inverse (for example, patterns like USDGSPC exist for indices; the yen may follow a similar convention). Keep the exact symbol you find there consistent across your requests and parsing logic.

Understand how quotes are expressed (base currency, units, and inverse keys)

The API returns prices relative to a base currency. In the official examples and the real sample below, the base is USD. When base = USD:

  • rates.XYZ is typically “USD per XYZ unit” (unit indicated by the “unit” or rate map semantics in the docs).
  • Some symbols also include an inverse convenience key like rates.USDXYZ when meaningful.
  • Timestamps are UNIX seconds; use them for ordering, caching, and cache invalidation.

For Japanese yen specifically, you’ll usually want USD/JPY (how many JPY for 1 USD) if you’re pricing dollar amounts in yen, or the inverse JPY/USD if you’re converting yen balances into dollars. Which side you need depends on your app; pick the appropriate key from the response map based on the symbol listing you verified earlier.

If your UI needs per-minute bars rather than snaps, combine periodic Latest snapshots with your own bar-builder. For daily backfill and close-to-close moves, use the time-series endpoint described in the Documentation.

Call the Latest endpoint (copy-paste curl)

Start by wiring the Latest endpoint. It returns the current map of rates with base, date, and timestamp. Replace YOUR_API_KEY with your key.

curl -s "https://indices-api.com/api/latest?access_key=YOUR_API_KEY"

Real API response (field names and structure you will parse)

Below is a real response sample from Indices-API. Note how the payload is wrapped in a top-level “data” envelope that contains success, timestamp, date, base, and the rates map.

{"data":{"success":true,"timestamp":1792629300,"date":"2026-10-22","base":"USD","rates":{"GSPC":0.00012890401935623,"USD":1,"USDGSPC":7757.709999999853}}}

What you’ll use in your code:

  • data.success: check before publishing.
  • data.timestamp: UNIX seconds for when the data snapshot was generated.
  • data.date: ISO date for display and backfill alignment.
  • data.base: pricing base, usually “USD”. Your math for conversions should respect this.
  • data.rates: a map keyed by symbol. In this sample, “GSPC” and the convenience “USDGSPC” inverse exist; for JPY you’ll parse the appropriate yen key you confirmed on the Symbols page.

Even though the example above shows GSPC to demonstrate the exact shape of the payload, your production parser should extract the JPY key you verified from the Symbols list.

WebSocket bridge: poll Latest and broadcast to clients

Most frontend frameworks prefer a single push channel that emits updates when there’s a new price. We’ll run a Node.js process that fetches Latest on a schedule aligned with your plan and pushes the yen rate to connected clients over WebSocket.

Practical polling guidance:

  • Update frequency: depending on plan, Latest updates every 60 minutes, every 10 minutes, or faster. Poll no more often than that; cache locally and only publish when the timestamp changes.
  • Retries: back off on network errors and keep your last known price until the next successful fetch.
  • Non-trading days: currency markets are 24/5. On weekends and holidays, expect no new timestamps; keep broadcasting the last valid snapshot and mark it stale in your UI.

JavaScript example: pull Latest and push over a WebSocket

This sample fetches Latest, extracts the yen symbol you configured from the symbols list, and emits messages to connected clients only when the API timestamp advances. It also shows a one-shot daily backfill using a separate function stub you can complete with the time-series endpoint documented in the API docs.

import http from 'http';
import fetch from 'node-fetch';
import WebSocket, { WebSocketServer } from 'ws';

const API_KEY = process.env.INDICES_API_KEY || 'YOUR_API_KEY';
const LATEST_URL = `https://indices-api.com/api/latest?access_key=${API_KEY}`;

// IMPORTANT: set this to the exact yen key you confirmed on the Symbols page.
// For example: 'JPY' or 'USDJPY' depending on how the Symbols listing defines yen.
const YEN_KEY = process.env.YEN_KEY || 'CONFIRM_ON_SYMBOLS_PAGE';

const PORT = process.env.PORT || 8080;

const server = http.createServer();
const wss = new WebSocketServer({ server });

let lastTimestamp = 0;
let lastPayload = null;

async function fetchLatest() {
  const res = await fetch(LATEST_URL, { timeout: 8000 });
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  const json = await res.json();

  // Data envelope as observed in the real sample.
  const data = json.data || json;

  if (!data.success) throw new Error('API success=false');

  // Only publish if there is a new snapshot.
  if (data.timestamp && data.timestamp !== lastTimestamp) {
    lastTimestamp = data.timestamp;

    const base = data.base;
    const date = data.date;
    const rates = data.rates || {};
    const yen = rates[YEN_KEY];

    // If yen key is absent, keep last payload and log.
    if (yen === undefined) {
      console.warn(`Latest snapshot missing key ${YEN_KEY}; verify on Symbols page.`);
      return;
    }

    lastPayload = {
      symbol: YEN_KEY,
      base,       // typically "USD"
      date,       // e.g., "2026-10-22"
      timestamp: data.timestamp, // UNIX seconds
      rate: yen   // numeric price for the configured key
    };

    const message = JSON.stringify({ type: 'yen_tick', payload: lastPayload });
    wss.clients.forEach((ws) => {
      if (ws.readyState === WebSocket.OPEN) ws.send(message);
    });
    console.log(`Broadcast ${YEN_KEY} @ ${yen} (t=${data.timestamp})`);
  }
}

function startPolling() {
  // Align with your plan's update interval:
  //  - poll every 60 minutes if your plan updates hourly,
  //  - poll every 10 minutes if your plan updates every 10 minutes, etc.
  // Here we default to 10 minutes (600_000 ms). Adjust as needed.
  const intervalMs = Number(process.env.POLL_MS || 600_000);

  // First tick immediately, then at interval.
  fetchLatest().catch(err => console.error('fetchLatest error:', err));
  setInterval(() => {
    fetchLatest().catch(err => console.error('fetchLatest error:', err));
  }, intervalMs);
}

// Optionally expose a simple HTTP endpoint for the last known price.
server.on('request', (req, res) => {
  if (req.url === '/last') {
    res.setHeader('Content-Type', 'application/json');
    res.end(JSON.stringify(lastPayload || { status: 'no_data' }));
  } else {
    res.statusCode = 404;
    res.end('Not found');
  }
});

wss.on('connection', (ws) => {
  // Send the last value on connect so charts render immediately.
  if (lastPayload) ws.send(JSON.stringify({ type: 'yen_tick', payload: lastPayload }));
});

server.listen(PORT, () => {
  console.log(`WebSocket server listening on :${PORT}`);
  startPolling();
});

// Backfill stub: implement with the time-series endpoint from the docs.
// Remember: end_date cannot be today; use yesterday.
// async function fetchDailyBackfill(startDate, endDate) { ... }

Clients connect to ws://your-host:8080 and subscribe to messages of type “yen_tick”. On connect, they’ll receive the last known price; subsequent messages publish on each new API timestamp. If your UI needs both sides of the quote (e.g., USD/JPY and JPY/USD), publish two symbols by reading both keys if your Symbols listing includes a direct and an inverse.

Backfill a recent series for charting and P&L

Charts look better with context. Use the time-series endpoint to fetch daily values between a start_date and an end_date and draw the baseline before the live stream starts. Practical notes:

  • Pick an end_date that is not today. The API may not accept “today” for finalized daily aggregates; set end_date to yesterday.
  • Weekends and holidays: for currency, some days may not produce daily bars in the same way as indices. If an API day is missing, synthesize from the last available or mark gaps in the UI.
  • Caching: cache the series per symbol+date-window. Invalidate when you detect a new trading day boundary in the Latest snapshot’s date or when your cache TTL elapses.

Because URL shapes and parameter options can evolve, follow the endpoint specification in the Documentation. Keep the ticker you verified for JPY consistent in your query so the returned rates map includes the yen key you expect.

Handling base currency, conversions, and “USDJPY vs JPYUSD” choices

Base is a key concept. When base = USD:

  • To display USD/JPY (how many JPY per USD): prefer the rates entry documented for yen that corresponds to “per USD” if available (e.g., a key like USDJPY if that is how it appears on the Symbols page).
  • To display JPY/USD (how many USD per JPY): use the direct JPY key if provided, or invert USD/JPY carefully with numeric precision considerations.
  • When publishing to clients, include base, timestamp, and the exact symbol so consumers can apply consistent math.

If you need a monetary conversion (e.g., converting 1,000 USD into JPY), consult the Convert endpoint in the Documentation. Keep unit semantics explicit in your messages to avoid accidental double-inversion on the frontend.

Update frequency, caching, and data freshness signals

The Latest endpoint updates at an interval determined by your plan (e.g., every 60 minutes or every 10 minutes). Polling more frequently won’t yield fresher data and only adds load. Recommended practice:

  • Set your poll interval to match or slightly exceed the plan’s update interval.
  • Only publish when data.timestamp increases; skip duplicates.
  • Expose timestamp and date to clients so they can render a staleness badge after a threshold (for example, if no new snapshot arrives after 1.5× your plan’s cadence).

Non-trading days, market hours, and Japan-specific timing

While the yen trades 24/5 across global FX venues, weekends and certain holidays will produce no new snapshots. Your service should:

  • Keep the last snapshot live on weekends and label it stale.
  • Roll caches at UTC midnight or at a time aligned with your analytics, not at arbitrary moments, to avoid splitting daily aggregates.
  • Be mindful of JST (UTC+9) if your product displays local dates or aligns alerts with local trading calendars. The API timestamps are UNIX seconds; convert on the client for display.

For macro-aware alerting, consult a reliable market calendar like the Bank of Japan schedule: Bank of Japan.

Operational tips that save debugging time

  • Health checks: expose a simple /last HTTP route (as in the example) so you can probe the running value in Kubernetes, Nomad, or ECS.
  • Schema locks: validate the presence of data.success, data.timestamp, data.base, and the yen key on every fetch; log if any are missing and avoid publishing partial messages.
  • Numeric safety: treat rates as floats; if you invert, keep at least double-precision and round for display only.
  • Backfills: pin end_date to yesterday; retry windows only on the next UTC day boundary to avoid flogging the service.

Where to find everything you need

You can also browse the main site for product context: indices-api.com.

FAQ

  • How often should I poll for a “live” WebSocket feed? Poll at the same cadence as your plan’s Latest update frequency (e.g., every 10 minutes). Only publish when the timestamp changes. Polling faster won’t improve freshness.
  • What timezone are dates and timestamps in? The payload includes a UNIX timestamp (UTC). The date field is ISO formatted; treat it as UTC for storage and convert to local time (e.g., JST) for display.
  • Why is today’s daily bar missing from the time-series? end_date cannot be today. Request up to yesterday. Daily aggregates for “today” are typically not finalized.
  • Which yen symbol should I parse: JPY, USDJPY, or something else? Do not guess. Confirm on the Symbols page and keep that key consistent across your Latest parsing and time-series backfills.
  • Can I get intraday candles? Use the intraday or OHLC endpoints described in the Documentation to build or fetch candles, or aggregate your own minute bars from repeated Latest snapshots.

Ready to stand up your JPY WebSocket feed? Grab a key and start shipping: Register. You’ll find all endpoint details and more examples in the Indices-API Documentation and the live indices-api.com site.

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