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Overview

This guide walks you through making your first HTTP API requests to discover terminals, initiate a payment, and check transaction status.

Prerequisites

Before you begin, ensure you have:

API Credentials

API key and API secret provided by Modulus Labs

HTTP Client

cURL, Postman, or HTTP client library for your language

JSON Parser

Ability to parse JSON responses

Network Access

Outbound HTTPS access to the API endpoint

Quickstart Flow

Step-by-Step Guide

1

Set up authentication

The HTTP API uses HMAC-SHA256 authentication. Each request requires three headers:See the Authentication page for detailed signature computation.
2

Discover available terminals

List all connected terminals in your group:
cURL
Response:
3

Initiate a payment

Send a payment request to a terminal. This endpoint uses long-polling and waits up to 90 seconds for the terminal to respond.
cURL
Successful Response (200 OK):
4

Check transaction status (optional)

If a payment times out or you need to verify status later:
cURL
Response:

Complete Code Examples

Error Handling

Handle common error scenarios:

Next Steps

Endpoints Reference

Complete HTTP endpoint documentation

Authentication

Detailed HMAC signature guide

Data Types

Shared data type reference

Core Concepts

Device enforcement and reconnection