Developers do not have to directly rely on the SDK to subscribe to the Stream API. Any language with a websocket client can directly subscribe to the Stream API and receive updates. The developer will need the following to subscribe:

• Base Endpoint:
  • Mainnet: wss://stream.openseabeta.com/socket/websocket
  • Testnet: wss://testnets-stream.openseabeta.com/socket/websocket
• API Key
• Collection they’d like to subscribe to
  • Can use * to subscribe to all
• Event types to subscribe to
  • item_metadata_updated
  • item_listed
  • item_sold
  • item_transferred
  • item_received_offer
  • item_received_bid
  • item_cancelled

  Step 1. Connecting

  Construct your full connection string as:
  **{base_endpoint}?token={api_key}**
  For example:
  wss://testnets-stream.openseabeta.com/socket/websocket?token=<API_KEY>
  And set up your client to connect to this endpoint. You should ping the Server every 30 seconds with a heartbeat message that should look as follows:
  JSON

  {
    "topic": "phoenix",
    "event": "heartbeat",
    "payload": {},
    "ref": 0
  }
  

  Step 2: Subscribing to a collection

  Figure out the slug of the collection you’d like to join and the event type you’d like to subscribe to. One current limitation is that you will only be able to subscribe to all events for this collection, and will therefore need to filter client-side as needed on event_types.
  Send the following message to subscribe to a collection:
  JSON

  {
    "topic": "collection:boredapeyachtclub",
    "event": "phx_join",
    "payload": {},
    "ref": 0
  }
  

  Keep track of the ref number used here, as it can be used later when unsubscribing

  Step 3: Unsubscribing from a collection

  To unsubscribe, you’ll need to just change the event field to phx_leave and pass in the same ref value used earlier. ref allows you to use multiple concurrent connection to different Collections as needed. You can also simply close your websocket client’s connection to disconnect.

  Example: Firecamp

  Firecamp is a popular API GUI client that supports making websocket requests. We’ve prepared a ready-to-use example in testnets that can be imported directly to your Firecamp app to see how we are able to connect to the Stream API and make requests. It also automatically pings for a heartbeat every 30 seconds to ensure your client remains connected.
  Stream API Example_firecamp.json
  Simply import this into your Firecamp UI to get a working, ready to use example of connecting to the Stream API Websocket
  Source for websocket connecting