About X402 Express

Project Overview

This project demonstrates how to use X402 payment system with Express.js, allowing API endpoints to charge for access using Solana USDC payments.

Project Structure

Server (src/index.ts): Express.js server with X402-protected API routes
Client (src/client.ts): Example client that automatically pays when calling protected endpoints
Routes (src/routes/index.ts): API routes with X402 payment middleware
Config (src/config.ts): Centralized configuration for payment settings (network, asset, amount, payment address)

Protected Route

The /api/protected endpoint requires a payment of 100 USDC to access. It uses X402 middleware to automatically verify and process payments.

Configuration

Payment configuration is centralized in src/config.ts. The following environment variables can be set to customize the payment settings:

PAY_TO_ADDRESS: Solana address to receive payments (defaults to a test address)
NETWORK: Solana network (defaults to "mainnet-beta")
ASSET: Token asset to use for payments (defaults to "USDC")
AMOUNT: Payment amount per request (defaults to "100")

Client Usage

The client demonstrates how to automatically pay for API access using X402:

Load your Solana keypair
Create a payment handler with X402
Wrap fetch to automatically handle payments
Call the protected endpoint (payment happens automatically)

X402 Middleware

X402 middleware is configured using centralized settings in src/config.ts:

Network: Solana mainnet-beta (configurable via NETWORK env var)
Asset: USDC (configurable via ASSET env var)
Amount: 100 USDC per request (configurable via AMOUNT env var)
Payment Address: Set via PAY_TO_ADDRESS env var
Facilitator: Handles payment verification at https://facilitator.corbits.io

The middleware automatically:

Validates incoming payment signatures
Verifies payment amounts
Grants access only after successful payment

Development

For detailed setup instructions, deployment guides, and code examples, please refer to the GitHub repository README.