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Overview

The Terminal Gateway enables communication between your POS (Point of Sale) system and payment terminals. Choose between two protocols based on your integration needs:
  • HTTP API - Synchronous request/response pattern with long-polling for payments
  • WebSocket API - Real-time bidirectional communication with push notifications
Version 1.0 - This documentation covers the current Terminal Gateway API. Contact support@moduluslabs.io to obtain your endpoint URL and credentials.

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Protocol Comparison

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Choosing a Protocol

HTTP API

Choose HTTP if you need:
  • Simple request/response pattern
  • Serverless or stateless architecture
  • Minimal client-side complexity
  • Occasional terminal interactions

WebSocket API

Choose WebSocket if you need:
  • Real-time terminal status updates
  • Instant payment notifications
  • Multi-terminal management
  • Persistent connection with push events

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API Endpoints

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Quickstart

1

Obtain API credentials

Contact support@moduluslabs.io to request API credentials. You’ll receive an API key and API secret pair.
2

Choose your protocol

Select HTTP for simple integrations or WebSocket for real-time features. See the protocol comparison above.
3

Follow the quick start guide

HTTP Quickstart

Get started with HTTP API

WebSocket Quickstart

Get started with WebSocket API

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Core Concepts

Both protocols share these core concepts:

Single Device Enforcement

One active connection per API key for security

Reconnection Resilience

60-second grace period for terminal reconnections during payments

Authentication

API key provisioning and authentication methods

Data Types

Shared schemas for payments, terminals, and errors

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Documentation Structure

HTTP API

WebSocket API

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Support

For technical support or questions about the Terminal Gateway:
  • Email: support@moduluslabs.io
  • Documentation: Browse the pages in this section for detailed implementation guides