nextBlock - Cardano

Example code for the nextBlock WebSocket method. Complete guide on how to use nextBlock WebSocket in GetBlock Web3 documentation.

This method requests the next chain-synchronization instruction. The node responds with either a forward roll to the next block or a backward roll to a previous point after a reorganization. This protocol requires a WebSocket connection.

Parameters

This method does not require parameters.

Request

JavaScript

example.js

import WebSocket from 'ws';

const client = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');

client.once('open', () => {
    client.send(JSON.stringify({"jsonrpc": "2.0", "method": "nextBlock", "id": "getblock.io"}));
});

client.on('message', (msg) => {
    console.log(JSON.parse(msg.toString()));
    client.close();
});

Python

example.py

import asyncio
import json
import websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({"jsonrpc": "2.0", "method": "nextBlock", "id": "getblock.io"}))
        print(json.loads(await ws.recv()))

asyncio.run(main())

Response

{
    "jsonrpc": "2.0",
    "method": "nextBlock",
    "result": {
        "direction": "forward",
        "block": {
            "era": "conway",
            "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f",
            "slot": 123456789,
            "height": 10453789
        },
        "tip": {
            "slot": 123456799,
            "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f"
        }
    },
    "id": "getblock.io"
}

Response Parameters

Field	Type	Description
direction	string	forward for a new block, or backward for a rollback
block	object	The block rolled forward to, present on a forward roll
point	object	The point rolled back to, present on a backward roll
tip	object	The node's current tip

Use Cases

• Chain Indexing: Stream blocks sequentially into an off-chain store

• Reorg Handling: React to backward rolls by rewinding local state

• Event Pipelines: Drive downstream processing from each new block

• Explorers: Ingest the chain block by block

Error Handling

Error Code	Message	Description
-32602	Invalid params	The supplied points are missing or malformed
1000	Intersection not found	None of the supplied points are on the node's chain
-32603	Internal error	The node failed to advance the chain-sync protocol