Market Data WebSocket

Overview

Priceboard Realtime streams live market data (matched quotes, bid/offer) over Socket.IO. It is a completely separate channel from Order & Account data — see Connecting to Order & Account for that.

This channel does not require an access token — you only need to connect and subscribe to the correct symbol.

Connection details

Setting	Value
Host (Production)	`https://flashapi.phs.vn`
Socket.IO path	`/ws/socket.io`
Transport	`websocket` (required — do not fall back to `polling`)
Client library	`socket.io-client`

The path must be exact. Using the wrong path (e.g. missing /ws) causes the server to return a 301 redirect to its documentation site instead of completing the Socket.IO handshake, which surfaces as a generic connection error on the client.

Connection steps

Initialize the client

Connect to the host + path above, forcing the websocket transport.

Subscribe to symbols

After the connect event, send each topic via the subscribe event (a plain string, not an object).

Listen for data

The server pushes updates through the publish event whenever a quote or bid/offer changes.

Example code (Node.js / JavaScript)

const io = require("socket.io-client");

const socket = io("https://flashapi.phs.vn", {
  path: "/ws/socket.io",
  transports: ["websocket"],
});

socket.on("connect", () => {
  console.log("Connected:", socket.id);

  // Subscribe per symbol — repeat for each symbol you want to track
  socket.emit("subscribe", "market.quoteKrx.ACB");
  socket.emit("subscribe", "market.bidofferKrx.ACB");
});

socket.on("publish", (data) => {
  console.log("Received:", data);
});

socket.on("connect_error", (err) => {
  console.error("Connection error:", err.message);
});

socket.on("disconnect", (reason) => {
  console.log("Disconnected:", reason);
});

Subscribe topic	Symbol (`<symbol>`)	Meaning
`market.quoteKrx.<symbol>`	e.g. `ACB`	Realtime matched quote
`market.bidofferKrx.<symbol>`	e.g. `ACB`	Bid/offer depth (3 price levels)

Field mapping for `publish`

Real sample response:

{
  "type": "publish",
  "data": {
    "s": "ACB", "rc": "ACB", "m": "HOSE",
    "n1": "Ngân hàng Thương mại Cổ phần Á Châu",
    "marketId": "STO", "ti": 1787642809879,
    "vo": 6489300, "va": 145709955000,
    "bb": [{"p":22300,"v":67700},{"p":22250,"v":167500},{"p":22200,"v":152500}],
    "bo": [{"p":22350,"v":5500},{"p":22400,"v":68300},{"p":22450,"v":144600}],
    "tbo": 0, "too": 0
  }
}

Field	Type	Meaning
`s`	string	Symbol
`rc`	string	Root code — usually the same as `s`
`m`	string	Exchange (Market) — e.g. `HOSE`, `HNX`, `UPCOM`
`n1`	string	Full listed company name
`marketId`	string	Market segment code (`STO` = underlying/stock)
`ti`	number	Update timestamp — Unix epoch in milliseconds
`vo`	number	Cumulative matched volume for the session
`va`	number	Cumulative matched value for the session, in VND
`bb`	array `{p, v}`	Best Bid book — up to 3 price levels; `p` = price (VND), `v` = order volume
`bo`	array `{p, v}`	Best Offer book — up to 3 price levels; `p` = price (VND), `v` = order volume
`tbo`	number	total bid order volume
`too`	number	total offer order volume

This payload combines quote and bid/offer data in a single publish event — there is no field indicating whether it originated from the quoteKrx or bidofferKrx topic. If subscribing to both for the same symbol, use s to identify the symbol and check for the presence/change of bb/bo to detect bid/offer updates.

Troubleshooting

Symptom	Likely cause	How to check
Connects but no `publish` events arrive	Wrong subscribe format (sent an object instead of a string), or wrong symbol	Log the exact topic string sent and compare against the format above
`connect_error` immediately on connect	Wrong `path`, wrong host, or client allows `polling` before `websocket`	Confirm `path: "/ws/socket.io"` and `transports: ["websocket"]`
Receives HTML / 301 instead of a Socket.IO handshake	Connected to the wrong path (e.g. the Order & Account path)	Confirm Priceboard uses `/ws/socket.io`, distinct from `/realtime/eqt(or fno)/socket.io` used by Order & Account

Next step

For realtime order, buying power, and portfolio data, see Connecting to Order & Account (EQT/FNO).

API documentation

Terms and conditions

Market Data WebSocket

Overview

Connection details

Connection steps

Example code (Node.js / JavaScript)

Field mapping for `publish`

Troubleshooting

Next step

​Overview

​Connection details

​Connection steps

​Example code (Node.js / JavaScript)

​Subscribe topic mapping

​Field mapping for publish

​Troubleshooting

​Next step

Overview

Connection details

Connection steps

Example code (Node.js / JavaScript)

Subscribe topic mapping

Field mapping for `publish`

Troubleshooting

Next step