❗️
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

Chain Group	Chains
Ethereum-Compatible	Ethereum, Base, Polygon, Arbitrum, Avalanche, Optimism
Solana	Solana
Polkadot	Polkadot, Kusama

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

Supported Methods	Event Types	Compute Units
`eth_subscribe`	`logs`	30 CU per block
	`newHeads`	5 CU per message
	`newPendingTransactions`	20 CU per second
`eth_unsubscribe`

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

Description	Count	CU per Action	Total CU
🔼 Open WebSocket connection	1	1 CU	1
🔼 Send `eth_subscribe` request	1	1 CU	1
🔽 Receive confirmation from node	1	1 CU	1
🔽 Receive `newHeads` messages	5	10 CU	50
🔼 Send `eth_unsubscribe` request	1	1 CU	1
🔽 Receive unsubscribe confirmation	1	1 CU	1
Total Compute Units			55 CU

Solana

Supported Methods	CU per Subscription	Subscribes To	CU per Message
`accountSubscribe`	1 CU	`accountNotification`	5 CU
`accountUnsubscribe`	1 CU

`logsSubscribe`	1 CU	`logsNotification`	5 CU
`logsUnsubscribe`	1 CU

`programSubscribe`	1 CU	`programNotification`	10 CU
`programUnsubscribe`	1 CU

`signatureSubscribe`	1 CU	`signatureNotification`	5 CU
`signatureUnsubscribe`	1 CU

`slotSubscribe`	1 CU	`slotNotification`	5 CU
`slotUnsubscribe`	1 CU

`slotsUpdatesSubscribe`	1 CU	`slotsUpdatesNotification`	5 CU
`slotsUpdatesUnsubscribe`	1 CU

- 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

Description	Count	CU per Action	Total CU
🔼 Send `accountSubscribe` request	1	1 CU	1
🔽 Receive confirmation response	1	1 CU	1
🔽 Receive `accountNotification` messages	8	5 CU	40
🔼 Send `accountUnsubscribe` request	1	1 CU	1
🔽 Receive unsubscribe confirmation	1	1 CU	1
Total Compute Units			44 CU

Polkadot

Supported Methods	CU per Subscription	Subscribes To	CU per Message
`beefy_subscribeJustifications`	1 CU	`beefy_justifications`	1 CU
`beefy_unsubscribeJustifications`	1 CU

`chain_subscribeFinalizedHeads`	1 CU	`chain_finalizedHead`	1 CU
`chain_unsubscribeFinalizedHeads`	1 CU

`chain_subscribeAllHeads`	1 CU	`chain_allHead`	1 CU
`chain_unsubscribeAllHeads`	1 CU

`chain_subscribeNewHeads`	1 CU	`chain_newHead`	1 CU
`chain_unsubscribeNewHeads`	1 CU

`grandpa_subscribeJustifications`	1 CU	`grandpa_justifications`	1 CU
`grandpa_unsubscribeJustifications`	1 CU

`state_subscribeRuntimeVersion`	1 CU	`state_runtimeVersion`	1 CU
`state_unsubscribeRuntimeVersion`	1 CU

`state_subscribeStorage`	1 CU	`state_storage`	5 CU
`state_unsubscribeStorage`	1 CU

- 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

Description	Count	CU per Action	Total CU
🔼 Send `state_subscribeStorage` request	1	1 CU	1
🔽 Receive confirmation response	1	1 CU	1
🔽 Receive `state_storage` notifications	6	5 CU	30
🔼 Send `state_unsubscribeStorage` request	1	1 CU	1
🔽 Receive unsubscribe confirmation	1	1 CU	1
Total Compute Units			34 CU

How to Connect

To connect to the WebSocket endpoint, follow these steps:

Authorize your request using one of the following methods:

curl --header "Authorization: Bearer YOUR_API_KEY"

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

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

Connect to the WebSocket URL with the following URL pattern:

wss://svc.blockdaemon.com/:protocol/:network/native

For example, for Ethereum Mainnet:

wscat --header "Authorization: Bearer YOUR_API_KEY" \
-c wss://svc.blockdaemon.com/ethereum/mainnet/native

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

// 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}