FLATSMS GATEWAY
An enterprise-grade cloud control plane and real-time WebSocket gateway transforming commodity Android devices with domestic SIM cards into programmable, API-addressable 2-way SMS telecommunication infrastructure.
DEMOCRATIZING ENTERPRISE SMS WITH PHYSICAL CELLULAR BRIDGES
Traditional CPaaS vendors (Twilio, MessageBird, Sinch) charge exorbitant rates—often exceeding $0.015 per message segment plus arbitrary carrier pass-through fees and onerous regulatory hurdles like A2P 10DLC registrations. For startups, bootstrapped SaaS products, and local enterprises, transactional SMS costs escalate uncontrollably. FlatSMS circumvents these costs by transforming affordable Android devices with unlimited carrier SMS plans into private, API-driven cellular gateway bridges.
Strict cryptographic tenant isolation ensures each organization operates within an independent sandbox with isolated API keys, encrypted message stores, dedicated queues, and device pulse telemetry.
HIGH-THROUGHPUT DISPATCH & REAL-TIME AUDIT TRAIL
Every message flows through a sub-second lifecycle: HTTP client ingestion → Redis BullMQ durability buffer → active WebSocket client push → native Android SmsManagercarrier transmission → asynchronous delivery report callback. The web console surfaces instantaneous status transitions with zero page refreshes.
SCOPED REST CREDENTIALS & SECURE MODAL WORKFLOW
Security was engineered with zero compromises. API keys use high-entropy generation with SHA-256 cryptographic hashing at rest. Plaintext secret keys are revealed strictly once upon creation inside an isolated, focused modal dialog, while the management console exposes only masked prefix identifiers.
fs_live_...) are shown exclusively once. Instant revocation terminates active connections immediately across all microservices.DEVELOPER-FIRST DOCUMENTATION & MULTI-LANGUAGE ENGINE
Adoption is determined by developer ergonomics. FlatSMS provides an interactive, in-app documentation playground featuring live copyable snippets across cURL, Axios, Node.js, PHP, and Python, complete with schema definitions and Bearer authentication guidance.
EVENT PROPAGATION & DETERMINISTIC RELIABILITY MATRIX
Two pillars underpin FlatSMS's production resilience: an HMAC-SHA256 signed webhook delivery pipeline that notifies external systems in real time, and an exhaustive, deterministic HTTP status catalog that eliminates ambiguous integration errors.
HMAC-SHA256 Webhook Verification
Configurable callback endpoints signed with secret tokens. Includes an embedded local test listener (/api/v1/webhooks/test-receiver) and cryptographic signature verifier.
Deterministic Error Matrix
Exhaustive HTTP response codes (400, 401, 404, 410, 429, 500) paired with strict machine-readable error enums (VALIDATION_ERROR, RATE_LIMIT_EXCEEDED) and structured JSON payloads.
THE COMPLETE TELECOMMUNICATION CONTROL SUITE
FlatSMS synthesizes modern cloud architecture, mobile system daemons, and cryptographic security into a singular, cohesive developer platform. From single OTP verifications to high-volume bulk dispatch pipelines, the entire infrastructure operates with complete autonomy.
Cloud Control Plane
Node.js ESM & Express 5 backend written in strict TypeScript. Implements Zod payload validations, JWT/API key authentication, and centralized WebSocket gateway streaming.
Native Android Daemon
Kotlin Android application running an unkillable Foreground Service. Integrates Android SmsManager for dispatch and a system BroadcastReceiver for inbound SMS interception.
Durable Queue Engine
Redis BullMQ cluster decoupling client HTTP latency from physical cellular radios. Features automatic retry backoffs (2s to 30s) and dead-letter handling.
React 19 Dashboard
Vite + React 19 + Tailwind CSS 4 web frontend. Real-time device pulse monitoring, QR device pairing, interactive documentation, and webhook signature verification studio.
BUILDING SCALABLE CLOUD SAAS OR REAL-TIME SYSTEMS?
Whether you require high-throughput WebSocket microservices, custom cellular gateways, or modern React/Node.js enterprise architectures, let's build production-grade software together.