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This guide shows how to create a wallet monitor using the Ton Center API.
It continuously polls the blockchain for the latest transaction and balance of a given wallet address, and alerts when new transactions are detected. This recipe is useful for:
  • Building bots that notify users of incoming/outgoing payments
  • Tracking balances for custodial or exchange wallets
  • Exploring and debugging account activity in real time
The examples use the public Ton Center endpoint:
https://toncenter.com/api/v2/jsonRPC
For production, you should request your own API key and use a dedicated endpoint for higher rate limits and stability.

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1. Fetching transactions

Transactions for an account can be retrieved via the getTransactions method. Example request: 
curl -X POST https://toncenter.com/api/v2/jsonRPC \
  -H "Content-Type: application/json" \
  -d '{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "getTransactions",
    "params": [{ "address": "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2", "limit": 1 }]
  }'

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2. Checking balance

To query the balance of an account, use the getAddressBalance method. Example request: 
curl -X POST https://toncenter.com/api/v2/jsonRPC \
  -H "Content-Type: application/json" \
  -d '{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "getAddressBalance",
    "params": ["EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2"]
  }'

​
3. Code Implementation

The script polls every 5 seconds and prints balance updates and new transactions.
  • JavaScript (@ton/core)
Install dependencies:
yarn add ton ton-crypto ton-core buffer
Code:
import { TonClient, Address } from "ton";

const client = new TonClient({
  endpoint: "https://toncenter.com/api/v2/jsonRPC",
});

const address = Address.parse(
  "EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2"
);

let lastSeenLt = null;

async function checkTransactions() {
  try {
    const txs = await client.getTransactions(address, { limit: 1 });
    const latest = txs[0];

    if (latest) {
      if (lastSeenLt && latest.lt !== lastSeenLt) {
        console.log("  New transaction detected!");
        console.log("  lt:", latest.lt, "hash:", latest.hash().toString("base64"));
      }
      lastSeenLt = latest.lt;
    }

    const balance = await client.getBalance(address);
    console.log("Current balance:", balance.toString(), "nanotons");
  } catch (err) {
    console.error("Error:", err.message);
  }
}

setInterval(checkTransactions, 5000);

console.log("Monitoring transactions for", address.toString());
Output example:
Monitoring transactions for EQDtFpEwcFAEcRe5mLVh2N6C0x-_hJEM7W61_JLnSF74p4q2
Current balance: 1317379090350631577 nanotons
  New transaction detected!
  lt: 61948272000003n
hash: LrWzfCoHKUSHK9RqgznOuZ841KG3eyEeo3uZbcy/Hzs=
Current balance: 1317379090350537050 nanotons

​
4. Use Cases

  • Notification bots – Send Telegram/Discord alerts when a user’s wallet receives or spends TON.
  • Custodial wallets – Exchanges or custodians can track balances in real time for hot wallets.
  • Developer debugging – Easily follow transaction activity while testing dApps or smart contracts.
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