subscribe - Cosmos

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

Subscribes to events matching a Tendermint event query over WebSocket. Use queries like tm.event='NewBlock', tm.event='Tx', or transfer.recipient='cosmos1...'. Returns a subscription that streams matching events as separate WebSocket messages.

WebSocket-only method. This method is only available over the WebSocket transport at wss://go.getblock.io/<ACCESS-TOKEN>/websocket. It will not work via HTTP POST. Use a WebSocket client such as wscat, the @cosmjs/tendermint-rpc WebSocketClient, or Python's websockets library.

Parameters

Parameter

Type

Required

Description

query

string

Yes

Tendermint event query string

Request Example

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

# Then send:
{"jsonrpc": "2.0", "method": "subscribe", "params": {"query": "tm.event='NewBlock'"}, "id": "getblock.io"}

import WebSocket from 'ws';

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

ws.on('open', () => {
    ws.send(JSON.stringify({
    "jsonrpc": "2.0",
    "method": "subscribe",
    "params": {
        "query": "tm.event='NewBlock'"
    },
    "id": "getblock.io"
}));
});

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

import asyncio
import json
import websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/websocket') as ws:
        await ws.send(json.dumps({
    "jsonrpc": "2.0",
    "method": "subscribe",
    "params": {
        "query": "tm.event='NewBlock'"
    },
    "id": "getblock.io"
}))
        async for message in ws:
            print(json.loads(message))

asyncio.run(main())

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>/websocket").await?;

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "subscribe",
        "params": {
                "query": "tm.event='NewBlock'"
        },
        "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": {}
}

Response Parameters

Field

Type

Description

result

object

Empty object on success — streamed events arrive as separate WebSocket messages

Use Cases

Real-time block notifications (tm.event='NewBlock')
Live transaction streaming (tm.event='Tx')
Per-account activity feeds (transfer.recipient='cosmos1...')
IBC packet flow monitoring
Governance event tracking

Error Handling

Status Code

Error Message

Cause

404

Not Found

Missing or invalid <ACCESS-TOKEN>

-32602

Invalid params

Request parameters are missing or malformed

-32603

Internal error

Server-side error while processing the request

429

Too Many Requests

Rate limit exceeded for your plan

-32603

Subscription limit exceeded

Each WebSocket connection has a maximum subscription count (typically 5)

-32602

Invalid query

Query string is malformed or references unknown event types

SDK Integration

import { Tendermint37Client, WebsocketClient } from '@cosmjs/tendermint-rpc';

const wsClient = new WebsocketClient('wss://go.getblock.io/<ACCESS-TOKEN>/websocket');
const client = await Tendermint37Client.create(wsClient);

// Use the typed subscription methods on the client where available.
// For raw subscription access:
const stream = wsClient.listen({"jsonrpc": "2.0", "id": "sub-1", "method": "subscribe", "params": {"query": "tm.event='NewBlock'"}});
stream.subscribe({
    next: (event) => console.log(event),
    error: (err) => console.error(err)
});

# cosmpy does not expose CometBFT WebSocket subscriptions directly.
# Use the `websockets` library as shown in the Request Example above.
import asyncio
import json
import websockets

async def stream():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/websocket') as ws:
        await ws.send(json.dumps({'jsonrpc': '2.0', 'id': 'sub-1', 'method': 'subscribe', 'params': {"query": "tm.event='NewBlock'"}}))
        async for msg in ws:
            print(json.loads(msg))

asyncio.run(stream())

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