subscriptions.md

In this session we'll demonstrate how to coordinate via the XRPL.

The XRPL is a public ledger, meaning that when you write on chain anyone can read. In this session we will demonstrate how to subscribe to events as they happen on chain.

First off we will create a pair of accounts:

import xrpl from "xrpl";

const serverURL = "wss://s.altnet.rippletest.net:51233"; // For testnet

const main = async () => {
  const client = new xrpl.Client(serverURL)
  await client.connect()

  // do something useful
  console.log("lets fund 2 accounts...")
  const { wallet: wallet1, balance: balance1 } = await client.fundWallet()
  const { wallet: wallet2, balance: balance2 } = await client.fundWallet()

  console.log("wallet1", wallet1)
  console.log("wallet2", wallet2)

  console.log({
    balance1,
    address1: wallet1.address, //wallet1.seed
    balance2,
    address2: wallet2.address,
  })

  // end
  client.disconnect()
};

main()

You'll check the logs and find the seed for both accounts, this is what we will use later to reuse these accounts deterministically.

Here is how we would generate a payment transaction between the two accounts.

import xrpl from "xrpl";

const serverURL = "wss://s.altnet.rippletest.net:51233"; // For testnet

const wallet1 = xrpl.Wallet.fromSeed("sEdVYquTyQbwn7URKzzdbJ6L4tx1n5u");
const wallet2 = xrpl.Wallet.fromSeed("sEdTxX3LJChazh9FDU51nVDd11n5nDQ");

// Call the function to read transactions

const main = async () => {
  const client = new xrpl.Client(serverURL);
  await client.connect();

  // do something useful
  console.log("funding wallet");
  console.log(
    wallet1.classicAddress,
    await client.getBalances(wallet1.classicAddress),
  );
  console.log(
    wallet2.classicAddress,
    await client.getBalances(wallet2.classicAddress),
  );

  const tx = {
    TransactionType: "Payment",
      Account: wallet1.classicAddress,
      Destination: wallet2.classicAddress,
      Amount: "1234",
  }

  const result = await client.submitAndWait(tx, {
    autofill: true,
    wallet: wallet1,
  });
  console.log(result)

  // end
  client.disconnect()
};

main()

One way to retrieve transactions for a given account is to simply create a request for transactions. Here is an example.

// ... define wallet1 before this point
const request = {
  command: 'account_tx',
  account: wallet1.classicAddress,
  ledger_index_min: -1, // To get transactions from all ledgers
  ledger_index_max: -1, // To get transactions up to the most recent ledger
  limit: 10, // Limit the number of transactions (optional)
}
const response = await client.request(request)
console.log('Account Transactions:', response.result.transactions)

And finally we will demonstrate how to listen for transactions affecting a given account, so as to catch all transactions. You could use this to build a notification bot that lets you know when anything happens to your account.

import xrpl from 'xrpl';

const serverURL = 'wss://s.altnet.rippletest.net:51233'; // For testnet
const walletAddress = 'rfwGxAj4B1NkBihbuL83CiGjvsp9BVzrKX'

const main = async () => {
  const client = new xrpl.Client(serverURL)
  await client.connect()

  // do something useful
    const subscriptionRequest = {
      command: 'subscribe',
      accounts: [walletAddress]
    };

    await client.request(subscriptionRequest)
    console.log(`Subscribed to transactions for account: ${walletAddress}`)

    // Event listener for incoming transactions
    client.on('transaction', (transaction) => {
      console.log('Transaction:', transaction);
    })

    // Event listener for errors
    client.on('error', (error) => {
      console.error('Error:', error);
    })

  // end
  // keep open
  console.log('all done')
}

main()
setInterval(() => {
  console.log('One second has passed!');
}, 1000)