Compute Unit (CU) values are subject to change as we assess and adjust our pricing to better reflect usage and associated costs.

Blockdaemon's RPC API supports WebSocket connections for real-time blockchain data on supported chains. This guide covers how to connect, which methods are available, and how Compute Units (CUs) are calculated.

Supported Chains

WebSocket Methods & Compute Units

Non-subscription RPC methods over web-socket connection are billed the same as regular RPC methods over HTTP.

• Ethereum
• Polkadot

Ethereum-Compatible Chains

• Subscribe / Unsubscribe request: 1 CU per request
• Confirmation responses: 1 CU
• Event messages (e.g., newHeads): CU varies by event type

The minimum charge is 1 CU per action.

Billing Example – Subscribe to eth_subscribe with newHeads

Solana

- Subscribe / Unsubscribe request: 1 CU per request - Confirmation responses: 1 CU - Event messages (e.g., slotNotification): CU varies by event type

Each subscription type has a specific event type tied to it. For example, you send slotSubscribe → you’ll receive messages of type slotNotification.

Billing Example – Subscribe to accountSubscribe and receive accountNotification

Polkadot

- Subscribe / Unsubscribe request: 1 CU per request - Confirmation responses: 1 CU - Event messages (e.g., chain_newHead): CU varies by event type

Each subscription type has a specific event type tied to it. For example, you send state_subscribeStorage → you’ll receive messages of type state_storage.

Billing Example – Subscribe to state_subscribeStorage and receive state_storage notifications

How to Connect

To connect to the WebSocket endpoint, follow these steps:

1. Authorize your request using one of the following methods:

   Bearer Token

   curl --header "Authorization: Bearer YOUR_API_KEY"
   

   API Key

   curl --header "X-API-KEY: YOUR_API_KEY"
   

2. You'll need to install a WebSocket client like wscat, or any other tool you prefer to connect.

    npm install -g wscat   //One-time installation
    ```

3. **Connect** to the WebSocket URL with the following URL pattern:

```undefined
    wss://svc.blockdaemon.com/:protocol/:network/native
    ```
    
    For example, for Ethereum Mainnet:
    
    ```undefined
    wscat --header "Authorization: Bearer YOUR_API_KEY" \
    -c wss://svc.blockdaemon.com/ethereum/mainnet/native
    ```

4. Once connected, you can **send and receive** messages using JSON-RPC:

JSON
    
    ```json
    // Subscribe to a WebSocket event (e.g., newHeads)
    {"jsonrpc":"2.0","method":"eth_subscribe","params":["newHeads"],"id":1}
    
    // Server responds with a subscription ID
    {"jsonrpc":"2.0","id":1,"result":"0xb544f3328760ac404b9e3a4aec6f2ec0"}
    
    // You’ll receive real-time updates as events happen
    {"jsonrpc":"2.0","method":"eth_subscription","params":{
      "subscription":"0xb544f3328760ac404b9e3a4aec6f2ec0",
      "result":{ /* event data */ }
    }}
    
    // To unsubscribe from the event stream
    {"jsonrpc":"2.0","method":"eth_unsubscribe","params":["0xb544f3328760ac404b9e3a4aec6f2ec0"],"id":2}
    
    // Confirmation that you’ve successfully unsubscribed
    {"jsonrpc":"2.0","id":2,"result":true}
    ```

## Need Help?

Contact us through [email](mailto:support@blockdaemon.com) or our [support page](/content/support/index.html) for any issues, bugs, or assistance you may need.