On-Chain Payments

Accept cryptocurrency payments on EVM-compatible blockchains. FluxKit monitors the blockchain for incoming payments and automatically confirms them.

Configuration

pay({
  onchain: {
    rpcUrl: process.env.RPC_URL,
    receiverAddress: process.env.PAYMENT_WALLET,
    supportedTokens: ["USDC", "USDT", "ETH"],
    supportedChains: ["ethereum", "arbitrum", "base"],
    confirmations: 3,               // Required block confirmations
    pollInterval: 15_000,           // Check every 15 seconds
    tokenAddresses: {
      USDC: {
        ethereum: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
        arbitrum: "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
        base: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      },
      USDT: {
        ethereum: "0xdAC17F958D2ee523a2206206994597C13D831ec7",
        arbitrum: "0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9",
      },
    },
  },
});

Creating a Payment Request

Programmatic

const payment = await app.pay.onchain.createPayment({
  amount: "29.99",
  token: "USDC",
  chain: "arbitrum",
  metadata: {
    userId: "user-123",
    orderId: "order-456",
  },
  expiresIn: "30m",
});

console.log(payment._id);             // Payment ID
console.log(payment.receiverAddress);  // Wallet address to pay
console.log(payment.amount);           // "29990000" (in token decimals)
console.log(payment.token);            // "USDC"
console.log(payment.chain);            // "arbitrum"
console.log(payment.status);           // "pending"

REST API

curl -X POST http://localhost:3000/pay/onchain/payment \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer eyJhbGci..." \
  -d '{
    "amount": "29.99",
    "token": "USDC",
    "chain": "arbitrum"
  }'

Response (200):

{
  "_id": "65a1b2c3d4e5f6a7b8c9d0e1",
  "receiverAddress": "0x1234...5678",
  "amount": "29990000",
  "displayAmount": "29.99",
  "token": "USDC",
  "tokenAddress": "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
  "chain": "arbitrum",
  "status": "pending",
  "expiresAt": "2025-01-15T11:00:00.000Z"
}

Checking Payment Status

Programmatic

const status = await app.pay.onchain.getPayment(paymentId);

if (status.status === "completed") {
  console.log(`Payment confirmed in tx ${status.txHash}`);
}

REST API

curl http://localhost:3000/pay/onchain/payment/65a1b2c3d4e5f6a7b8c9d0e1 \
  -H "Authorization: Bearer eyJhbGci..."

Response (200) -- confirmed:

{
  "_id": "65a1b2c3d4e5f6a7b8c9d0e1",
  "status": "completed",
  "amount": "29990000",
  "token": "USDC",
  "chain": "arbitrum",
  "txHash": "0xabc123...",
  "blockNumber": 12345678,
  "confirmations": 5,
  "completedAt": "2025-01-15T10:35:00.000Z"
}

Payment Events

app.pay.onchain.on("payment.confirmed", async (payment) => {
  console.log(`Payment ${payment._id} confirmed`);
  // Fulfill the order
});

app.pay.onchain.on("payment.expired", async (payment) => {
  console.log(`Payment ${payment._id} expired`);
});

Supported Tokens

Token	Decimals	Chains
ETH	18	Ethereum, Arbitrum, Base
USDC	6	Ethereum, Arbitrum, Base
USDT	6	Ethereum, Arbitrum

Environment Variables

Variable	Default	Description
RPC_URL	--	Default EVM RPC endpoint
PAYMENT_WALLET	--	Receiver wallet address
ONCHAIN_CONFIRMATIONS	3	Required confirmations
ONCHAIN_POLL_INTERVAL	15000	Polling interval in ms