subscribe - Nervos

Example code for the subscribe JSON-RPC method. Complete guide on how to use subscribe JSON-RPC in GetBlock Web3 documentation.

Subscribes to a topic over WebSocket. Available topics: new_tip_header (new tip headers), new_tip_block (new tip blocks with transactions), new_transaction (new transactions entering the pool), proposed_transaction (transactions moved to proposed state), rejected_transaction (transactions rejected from the pool). Returns a subscription ID; events arrive as separate WebSocket messages.

WebSocket-only method. This method is part of the Subscription module and is only available over the WebSocket transport at wss://go.getblock.io/<ACCESS-TOKEN>/. It will not work via HTTP POST.

Parameters

Parameter	Type	Required	Description
topic	string	Yes	One of new_tip_header, new_tip_block, new_transaction, proposed_transaction, rejected_transaction

Request Example

cURL

# WebSocket-only method. Use wscat (or similar) to connect first:
wscat -c 'wss://go.getblock.io/<ACCESS-TOKEN>/'

# Then send:
{"jsonrpc": "2.0", "method": "subscribe", "params": ["new_tip_header"], "id": "getblock.io"}

JavaScript (Axios)

import WebSocket from 'ws';

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

ws.on('open', () => {
    ws.send(JSON.stringify({
    "jsonrpc": "2.0",
    "method": "subscribe",
    "params": [
        "new_tip_header"
    ],
    "id": "getblock.io"
}));
});

ws.on('message', (data) => {
    console.log(JSON.parse(data.toString()));
});

Python (Requests)

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": "subscribe",
    "params": [
        "new_tip_header"
    ],
    "id": "getblock.io"
}))
        async for message in ws:
            print(json.loads(message))

asyncio.run(main())

Rust (Reqwest)

use tokio_tungstenite::connect_async;
use tokio_tungstenite::tungstenite::Message;
use serde_json::json;
use futures_util::{SinkExt, StreamExt};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (mut ws_stream, _) = connect_async("wss://go.getblock.io/<ACCESS-TOKEN>/").await?;

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "subscribe",
        "params": [
                "new_tip_header"
        ],
        "id": "getblock.io"
});
    ws_stream.send(Message::Text(payload.to_string())).await?;

    while let Some(msg) = ws_stream.next().await {
        println!("{:?}", msg?);
    }
    Ok(())
}

Response Example

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0xf1"
}

Response Parameters

Field	Type	Description
result	string	Subscription ID — used to match incoming notifications and to call unsubscribe

Use Cases

• Real-time block notifications for indexers

• Live wallet activity (subscribe to new_transaction filtered to your address)

• Mempool monitoring dashboards

• Detecting rejected transactions for RBF logic

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid <ACCESS-TOKEN>
-32602	Invalid params	Request parameters are missing or malformed
-32601	Method not found	Method does not exist or is not enabled on this node
-32603	Internal error	Server-side error while processing the request
429	Too Many Requests	Rate limit exceeded for your plan
-32600	Invalid Request	subscribe was called over HTTP; use a WebSocket connection instead
-32602	Invalid topic	Topic string is not one of the supported topics

SDK Integration

@ckb-lumos/lumos / ws

// Lumos doesn't expose CKB subscription methods directly. Use a raw
// WebSocket as shown in the Request Example above, or use the @ckb-ccc/core
// subscription helpers if available.
import WebSocket from 'ws';

const ws = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');
ws.on('open', () => {
    ws.send(JSON.stringify({
        jsonrpc: '2.0',
        id: 'sub-1',
        method: 'subscribe',
        params: ["new_tip_header"]
    }));
});
ws.on('message', (data) => console.log(JSON.parse(data.toString())));

websockets (Python)

# CKB SDK Python doesn't expose subscriptions directly — use websockets.
import asyncio, json, websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({
            'jsonrpc': '2.0', 'id': 'sub-1',
            'method': 'subscribe', 'params': ["new_tip_header"]
        }))
        async for msg in ws:
            print(json.loads(msg))

asyncio.run(main())