Tendrl

Docs / Contact / sdks/overview

SDKs & Clients

Tendrl provides official SDKs and clients to connect your devices, services, and applications to the Contact platform. Each SDK handles authentication, message batching, offline resilience, and reconnection so you can focus on your application logic.

Choose Your SDK

SDK Language Best For Protocol
Python SDK Python 3.8+ Servers, Raspberry Pi, data pipelines HTTPS
Go SDK Go 1.21+ High-performance services, edge gateways HTTPS
JavaScript SDK JavaScript/Node.js 16+ Web apps, Node.js services, React dashboards HTTPS
MicroPython Client MicroPython ESP32, Pico W, embedded microcontrollers MQTT
Nano Agent Any (Unix socket) Language-agnostic local gateway, high-throughput HTTPS

Quick Comparison

Feature Matrix

Feature Python Go JavaScript MicroPython Nano Agent
Message publishing Yes Yes Yes Yes Yes
File transfer² Yes Yes Yes Yes No
Inbound routing Yes (@client.on()) Yes (client.On()) Yes (client.on()) Yes (@client.on()) Callback only
Inbound state Yes (@client.on_state(), poll) Yes (@client.on_state(), poll) Yes (client.onState(), poll) Yes (@client.on_state(), MQTT push) No
Dynamic batching Yes Yes Yes Yes Yes
Offline storage SQLite BoltDB IndexedDB BTree BoltDB
Automatic heartbeats Yes Yes No Yes Yes
Manual heartbeat method No Yes Yes No Yes
State table (write) REST¹ REST¹ Yes Yes Yes
State table (read) REST¹ REST¹ Yes REST¹ Yes
Tether decorator Yes Yes No Yes No
Video streaming No No No Yes No
On-device vision No No No Yes (OpenMV) No
Remote deployment (OTA)³ No No No Yes (add-on) No
React hooks No No Yes No No
Headless mode Yes Yes No No No

¹ REST = no SDK wrapper; call the /entities/status-table REST endpoints directly (GET to read, PATCH to merge, PUT to replace). The MicroPython client can _write_ state over MQTT (update_state/replace_state) but has no on-device read, so read it back over REST.

² File transfer = send_file / check_files / download_file (Go/JS use SendFile/CheckFiles/DownloadFile). Files are scanned by Surface before delivery and are deleted on download. See File Transfer.

³ Remote deployment (OTA) = pushing application code to a device from the dashboard with automatic rollback, via the updater add-on. Selected at provision time (on by default for Full). See Remote Deployments.

Heartbeats: "Automatic" means the client sends heartbeats on its own once started (no code needed). A "manual heartbeat method" lets you push a heartbeat with your own system metrics on demand. The JavaScript SDK has no system-metrics source, so it exposes only the manual sendHeartbeat method and does not send heartbeats automatically.

Operating Modes

Most SDKs support two modes:

The Nano Agent is a standalone binary that provides managed-mode features to any language via a local Unix socket. Use it when your language doesn't have an SDK or when you want a single process handling all Tendrl communication.

Common Concepts

All SDKs share the same core patterns:

Authentication

Every SDK authenticates with an API key tied to a Contact entity. You can pass it directly or set the TENDRL_KEY environment variable.

Publishing Messages

code

client.publish(data, tags)

Messages are JSON objects sent to Contact. Tags control how messages are routed to flows and connectors. All SDKs accept any JSON-serializable data.

Receiving Messages

Pass a callback when constructing the client, or use tag-based routing (@client.on() on MicroPython, client.On() on Go, client.on() on JavaScript). The SDK delivers incoming messages automatically; see each SDK's Getting Started page.

State Table

Each entity has a persistent key-value state table:

Not every client wraps all three. The JavaScript SDK and Nano Agent expose read/update/replace directly; MicroPython exposes update/replace only; Python and Go have no state-table wrappers. In every case you can manage state over the /entities/status-table REST endpoints (GET / PATCH / PUT). See the feature matrix above.

Offline Resilience

When the network is unavailable, messages are stored locally and retried automatically when connectivity returns. Each SDK uses a storage engine appropriate for its platform.

Next Steps

Pick the SDK that fits your stack and follow the Getting Started guide:

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