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Subscribe to Blockchain Events

You can subscribe to different blockchain events in real time using subscription endpoints. Use filters to listen for particular contract addresses, account addresses, and/or token IDs.

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Subscribing to Events

Sequence Indexer SubscribeEvents Method:
  • Request: POST /rpc/Indexer/SubscribeEvents
  • Content-Type: application/json
  • Body (in JSON):
    • Filters ([]object) — an array of filters
      • contractAddresses ([]string) — a ERC20 / ERC721 / ERC1155 contract address
      • accounts ([]string) — wallet addresses
      • tokenIDs ([]int) optional — an array of token ids
      • events ([]string) — an array of event names
      • topicHashes ([]string) — an array of topic hashes
One of contractAddresses, accounts must be provided in the filter.

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Subscribing to Balance Updates

Sequence Indexer SubscribeBalanceUpdates Method:

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Subscribing to Receipts

Sequence Indexer SubscribeBalanceUpdates Method: Example SubscribeEvents 
curl -X POST \
  -H 'Content-type: application/json' \
  -H "X-Access-Key: c3bgcU3LkFR9Bp9jFssLenPAAAAAAAAAA" \
  https://polygon-indexer.sequence.app/rpc/Indexer/SubscribeBalanceUpdates \
  -d '{"contractAddress":"0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359"}'

import (
  "context"
  "log"

  "github.com/0xsequence/go-sequence/indexer"
  "github.com/0xsequence/go-sequence/lib/prototyp"
)

func SubscribeEvents() {
  seqIndexer := indexer.NewIndexer("https://polygon-indexer.sequence.app", "c3bgcU3LkFR9Bp9jFssLenPAAAAAAAAAA")

  reader, err := seqIndexer.SubscribeEvents(
    context.Background(),
    &indexer.EventFilter{
      ContractAddresses: []prototyp.Hash{prototyp.HashFromString("0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359")},
    },
  )
  if err != nil {
    log.Fatalf("SubscribeEvents: %v", err)
  }

  for {
    event, err := reader.Read()
    if err != nil {
      log.Fatalf("Read: %v", err)
    }

    log.Println("Event", event)
  }
}

// Works in both a Webapp (browser) or Node.js:
import { SequenceIndexer, WebrpcError } from '@0xsequence/indexer'

const indexer = new SequenceIndexer('https://polygon-indexer.sequence.app', 'c3bgcU3LkFR9Bp9jFssLenPAAAAAAAAAA')

const req = {
    filter: {
      contractAddresses: ['0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359'],
    },
}

const options = {
  onMessage: (msg: any) => {
    console.log('msg', msg)
  },
  onError: (err: WebrpcError) => {
    console.error('err', err)
  }
}

await indexer.subscribeEvents(req, options)