Using Relayer for Sending Transactions

In this tutorial, we will explore how to use the Relayers to send transactions. We will cover:

Checking relayer information.
Sending a transaction.
Checking the relayer status.

By the end of this tutorial, you will have a basic understanding of how to use the Relayer to interact with smart contracts.

Pre-requisites

OpenZeppelin Defender account. You can sign up to Defender here.
NodeJS and NPM
Typescript for Node js
Any IDE or text editor

1. Set Up Relayer

Let’s start by creating a Relayer:

Open Defender Operate & Automate in a web browser.
Click on Create Relayer with the name ETH Sepolia Relayer and Sepolia network.
Fund it with some Sepolia ETH. This relayer will send and pay for the automated transactions.
To create an API key for a Relayer, click on the Relayer and then on the More button to expand the dropdown and select Create API Key
Now you can set API key expiration in minutes, hours or days.
Once the API Key is created, make sure to write down the secret key. The API secret is only visible once during the creation — if you don’t write it down, it’s lost forever.

2. Check Relayer Information

Let’s start by checking the information of our relayer.
Add Relayer in .env File
Edit .env file in your project root directory and add your Relayer API Key and Secret:
```
RELAYER_API_KEY=your_api_key
RELAYER_SECRET_KEY=your_api_secret
```
Create a file named storeObject.ts in the project.

Now let’s add the following code:

const { Defender } = require('@openzeppelin/defender-sdk');

const dotenv = require('dotenv');

dotenv.config();

async function main() {

const client = new Defender({

relayerApiKey: process.env.RELAYER_API_KEY,
relayerApiSecret: process.env.RELAYER_SECRET_KEY,
});

const info = await client.relaySigner.getRelayer();
console.log('Relayer Info:', JSON.stringify(info, null, 2));

}

main().catch((error) => {
console.error(error);
process.exitCode = 1;
});

Execute the script to check the relayer information:

ts-node storeObject.ts

Alternatively, if you want to use Node directly:

node storeObject.js

3. Send Transaction

Next, we will send a transaction using the relayer.

Let’s edit the same file and add the following code:

const tx = await client.relaySigner.sendTransaction({
    to: '0x1B9ec5Cc45977927fe6707f2A02F51e1415f2052',
    speed: 'fast',
    data: '0x6057361d000000000000000000000000000000000000000000000000000000000000000a',
    gasLimit: '80000',
  });
console.log('Transaction sent! Hash:', tx.hash);

Here we are using the Sepolia Box contract as the target, which is:

0x1B9ec5Cc45977927fe6707f2A02F51e1415f2052

and data is the encoded version of the store() function with ‘10’ as input parameter.

0x6057361d000000000000000000000000000000000000000000000000000000000000000a

Execute the script to send a transaction:

ts-node storeObject.ts

Alternatively, if you want to use Node directly:

node storeObject.js

4. Check Transaction Status

Finally, let’s check the status of our transaction status.

Edit the file again and add the following code:

const txUpdate = await client.relaySigner.getTransaction(tx.transactionId);
console.log('Tx Status', JSON.stringify(txUpdate, null, 2));

Execute the script to check the relayer status:

ts-node storeObject.ts

Alternatively, if you want to use Node directly:

node storeObject.js

5. Next Steps

Congratulations! You have successfully used the Relayer to check information, send transactions, and verify the transaction status. By following this tutorial, you have gained a fundamental understanding of how to interact with smart contracts using the Relayer.

For more information on using Relayer, refer to the Relayers documentation.
Explore the Actions to automate your smart contract operational tasks with easy integration with the rest of Defender.