Easiest Way to Listen to Solana Events

Listening to Events on Solana: A Step-by-Step Guide

Welcome! Today, we’re going to do a hands-on project where we’ll build an app that listens to Solana events in real-time. This is a great way to start exploring how Solana works and how you can build decentralized applications (dApps) that react to blockchain events as they happen.

We’ll walk through every step, including setting up a Solana connection, listening to logs, filtering events, and processing them in real-time. Ready? Let’s go!

Step 1: Set Up Your Solana Project

First, let’s get our project set up. If you haven’t done so already, you’ll need to install the Solana Web3.js library, which allows us to interact with the Solana blockchain. Open your terminal and run the following command to install it:

npm install @solana/web3.js

Now that the library is installed, let’s start writing our code. We’re going to create a simple JavaScript file that connects to Solana and listens to events.

Step 2: Connect to Solana

We’ll start by connecting to the Solana blockchain. In Solana, we use something called an RPC (Remote Procedure Call) endpoint to interact with the network.

Create a new JavaScript file, let's call it listenForEvents.js. Inside this file, add the following code to connect to Solana:

import { Connection, PublicKey } from "@solana/web3.js";

// Replace with your actual Solana program ID
const PROGRAM_ID = new PublicKey("YOUR_PROGRAM_ID_HERE"); // Example: new PublicKey('your-program-id');

// The URL for Solana's RPC endpoint (you can use public RPCs or set up your own)
const URL = "https://api.mainnet-beta.solana.com"; // Mainnet RPC URL

// Create the connection to Solana network
const connection = new Connection(URL, "confirmed");

What’s Happening Here?

We imported Connection and PublicKey from the @solana/web3.js library.
We defined the PROGRAM_ID – this is the public key of the smart contract (program) on Solana you want to listen to.
We set up a connection to Solana’s mainnet (the main Solana network). You can use a different endpoint for test networks if you prefer.

Step 3: Listen for Logs (Events) from the Program

Now, we’re going to listen for logs that come from our Solana program. Logs are like notifications or messages that the program sends when something happens.

We can use the onLogs() function to listen for logs in real-time. Here’s how we do it:

// Listen for logs from the specified program
connection.onLogs(PROGRAM_ID, async (logInfo) => {
  const logs = logInfo.logs;

  // Loop through each log to find specific events
  for (const log of logs) {
    console.log("Log Detected:", log);

    // Check if the log contains the specific event we are interested in
    if (log.includes("Instruction: <event-name>")) {
      const event = extractEventData(logs);
      console.log({ event });
    }
  }
});

console.log(`Listening for events from program: ${PROGRAM_ID.toString()}`);

What’s Happening Here?

onLogs(PROGRAM_ID, callback): This tells Solana, “Hey, please notify me whenever there’s a log related to my program.” The callback function will be called each time a new log comes in.
logInfo.logs: This is where all the logs are stored. We’ll go through each log to check if it contains the event we’re interested in.
log.includes("<event-name>"): Replace <event-name> with the actual name of the event you’re trying to listen for. If it matches, we process it further.

Step 4: Extract and Process the Event Data

Once we detect an event, we’ll need to process the data inside the log. This data could be things like transaction amounts, sender and receiver addresses, and more, depending on the event.

Let’s create a simple function to extract and log the event data. This is just a basic example of how you might start processing the event.

// Simple function to extract event data from the logs
function extractEventData(logs) {
  // This is a placeholder. You can parse the log based on the structure of your specific event.
  // For example, you might extract transaction details, token amounts, etc.
  const eventData = {
    logs,
    timestamp: new Date(),
  };
  return eventData;
}

What’s Happening Here?

extractEventData(logs): This function is where we’ll handle the log data. For now, it’s just a placeholder that returns the logs and the current timestamp, but you can expand it to extract specific information based on the event’s structure.

Step 5: Real-Time Event Handling

Now, the cool part – real-time event handling! Once you run this code, the program will continuously listen to the Solana blockchain for new logs. Whenever a new log (event) is detected, your program will immediately process it.

To run your script, use the following command in your terminal:

node listenForEvents.js

You should start seeing logs printed in the console every time an event happens on the program you’re listening to.

Recap of What We’ve Done

Set up the connection: We connected to the Solana network using the RPC endpoint.
Listened for logs: We used onLogs() to listen to logs from a specific Solana program (smart contract).
Filtered events: We filtered the logs to detect specific events we’re interested in.
Processed events: We set up a function to process and extract the event data.

Conclusion

And that’s it! You’ve just built a simple app that listens to events on the Solana blockchain in real-time. This is an exciting first step toward building more complex decentralized applications. Solana’s fast and scalable network makes it a great choice for real-time apps.

I hope this guide was helpful! If you have any questions or need further clarification, feel free to ask in the comments. Happy coding! 🚀