findIntersection - Cardano

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

This method finds the intersection between the node's chain and a set of candidate points supplied by the client. It is the first step of the chain-synchronization protocol and sets the position from which nextBlock streams. This protocol requires a WebSocket connection.

Parameters

Parameter	Type	Required	Description
points	array	Yes	Candidate points, each a slot and block id, newest first

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": "findIntersection", "params": {"points": [{"slot": 123456789, "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f"}]}, "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": "findIntersection", "params": {"points": [{"slot": 123456789, "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f"}]}, "id": "getblock.io"}))
        print(json.loads(await ws.recv()))

asyncio.run(main())

Response

{
    "jsonrpc": "2.0",
    "method": "findIntersection",
    "result": {
        "intersection": {
            "slot": 123456789,
            "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f"
        },
        "tip": {
            "slot": 123456799,
            "id": "3e6f2d8c9a1b4e7f0c2d5a8b1e4f7a0c3d6b9e2f5a8c1d4e7b0f3a6c9d2e5b8f"
        }
    },
    "id": "getblock.io"
}

Response Parameters

Field	Type	Description
intersection	object	The point found on both the client's list and the node's chain
tip	object	The node's current tip at the time of intersection

Use Cases

• Sync Start: Set the starting point for streaming blocks

• Resumption: Resume synchronization from the last processed point

• Reorg Recovery: Re-anchor after a rollback by offering recent points

• Checkpointing: Confirm a known point is still on the node's chain

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