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If you need an API key, sign up here. WebSockets are reliable, well established and easily accessible - natively supported both in-browser (JavaScript) and server-side, with libraries and example code available in most programming languages.

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Table of Contents

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Fundamentals

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Basic Flow - Connect, Auth, Subscribe

  1. Connect to wss://fastforex.wsdx.io (and receive a connect message from the server)
  2. Send an auth message with your API key (get a free API key here)
  3. Send a subscribe message naming the stream you want, plus the desired pairs or instruments

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Streams - FX and Metals

The same connection serves both FX trading pairs and metals instruments. You choose which by setting stream on your subscribe message. Everything else works identically across the four - the same auth flow, the same message shapes, and the same price payload. Only the stream value and the symbols you subscribe to change. Use the symbols from /metals/instruments for the metals streams, and /fx/pairs for the FX streams. You can subscribe to more than one stream on a single connection - send a subscribe message for each. Access is granted per stream. If your plan does not include a stream, subscribing to it returns a 403 with No access to requested stream.

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JSON Message Format & Examples

Messages are sent and received in JSON format. All messages have an op field, which indicates the operation type. Messages from the server (“downstream”) will usually contain
  • a status field, which indicates the success or failure of the operation.
  • We follow HTTP status codes for this. e.g. 200 = success, 401 = not authenticated, etc.
  • a tsp field which indicates the timestamp of the message in milliseconds since epoch (Unix time).

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Upstream (sent to the WebSocket server)

Auth
Subscribe (FX)
Subscribe (Metals)

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Downstream

Connect (sent by server on connect)
Auth Response
Subscribe Response
Price
Metals prices arrive in the same shape, with the instrument symbol in sym

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Limitations, Message Volumes

Depending on your subscription plan, you may be limited on the number of concurrent WebSocket connections you can make, and to the maximum number of pairs per connect. Our standard offering allows for 2 connections and up to 5 pairs per connection. Contact us for higher limits. The symbol allowance is shared across streams on a connection - FX pairs and metals instruments count towards the same total. Subscribing to 5 FX pairs on a 5 symbol plan leaves no room for metals on that connection. Use a second connection, or spread your symbols across both. Subscribing beyond your allowance does not fail outright. The server subscribes you to as many symbols as it can and replies 429 with Capping concurrent symbols, so check the status on your subscribe response.
Warning - High Message Volume Popular pairs such as EURUSD can generate a lot of messages at peak times - up to hundreds of messages per second. Your application should be able to handle this. Connections may be closed if you cannot consume at the publish rate. Depending on your application needs, when sending your subscribe message, you can choose to use the fx1s or metals1s streams, which will produce at most one message per second, per subscribed symbol.

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Examples, Demos, Code Snippets & Client Libraries

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WebSocket Playground

WebSocket King is a great in-browser tool for testing WebSocket connections. You’ll need the following information and example payloads to get started:

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JSFiddle (JavaScript) Example

A really simple in-browser, native JavaScript example of connecting to the WebSocket server, authenticating and subscribing to a stream. https://jsfiddle.net/ycquz7px/