ping

basic-402

Minimal Express TypeScript server with x402 402 paywall.

• Requires USDC payment to access GET /ping.
• Default network: base-sepolia.

Setup

cd basic-402
cp .env.example .env
# edit PAY_TO to your EVM address
npm i
npm run dev

Open http://localhost:3000/ping. Without payment, you should get 402 with payment requirements or a paywall page. After paying with an x402 client, response will be { "message": "pong" }.

cURL

• Request without payment (JSON):

curl -i -H "Accept: application/json" http://localhost:3000/ping

• Request with paywall HTML (browser-like Accept):

curl -i http://localhost:3000/ping

• After generating an x402 payment header, include it to get pong:

# Replace <BASE64_XPAYMENT> with the value produced by an x402 client (e.g., x402-axios)
curl -i -H 'X-PAYMENT: <BASE64_XPAYMENT>' http://localhost:3000/ping

• Pretty-print the 402 JSON response:

curl -s -H "Accept: application/json" http://localhost:3000/ping | jq .

On success, the response will include the X-PAYMENT-RESPONSE header and a JSON body { "message": "pong" }.

Generate X-PAYMENT header and call with curl

1. Configure payer credentials (testnet):

cp .env.example .env
# set PRIVATE_KEY to the payer EVM private key (Base Sepolia recommended)
# set TARGET_URL if different

2. Generate header:

npm run payment:header
# outputs a long Base64 string

3. Use the header with curl:

HEADER=$(npm run -s payment:header)
curl -i -H "X-PAYMENT: $HEADER" $TARGET_URL

Notes:

• The script first fetches /ping to read accepts from the 402 JSON, then signs an exact EVM payment using PRIVATE_KEY and prints the header.
• Works by default for base-sepolia.