Azure Iot Hub

Azure IoT Hub is the enterprise-grade IoT connectivity layer — designed for millions of devices sending telemetry at scale. Key capabilities for agents: (1) Device Registry: query registered devices, check connection status. (2) Device Twin: update desired properties to push configuration to devices; read reported properties. (3) Direct Methods: invoke RPC-style calls on connected devices. (4) Cloud-to-Device messaging. Free tier (F1: 8000 messages/day). Confidence is docs-derived.

REST API at {iot-hub-name}.azure-devices.net. Resources: devices, device twins, direct methods, jobs. GET /devices/{id} retrieves device info. GET /twins/{id} retrieves device twin. PATCH /twins/{id} updates desired properties. POST /twins/{id}/methods invokes a direct method. GET /devices?top=100 lists devices. POST /messages/devicebound sends C2D message. IoT Hub built-in endpoint reads telemetry (Event Hub-compatible API). Response: JSON.

SAS token auth (primary): generate SharedAccessSignature from connection string. Azure AD (service principal) also supported. Per-policy scopes: service (send C2D, read D2C), registry (manage devices), device (connect devices). SAS tokens are time-limited; automate renewal. HTTPS for REST; MQTT/AMQP for device connections. TLS enforced. Managed Identity support for Azure-hosted services.

401 for invalid SAS token (expired or malformed), 404 for unregistered device, 409 for ETag conflict. Direct method: returns device-reported status; 408 if device doesn't respond within timeout. SAS token expiry is a common operational issue — automate renewal. IoT Hub SLA: 99.9% for basic/standard tiers. Throttling: 429 with retry-after. Bulk operations via jobs API.

docs.microsoft.com/azure/iot-hub is comprehensive Microsoft Learn documentation — quickstarts, tutorials, architecture guides. Device SDKs: Python (azure-iot-device), Node.js (azure-iothub), Java, .NET, C. Service SDK for cloud-side operations. Getting started: create IoT Hub in Azure Portal (free tier F1), register a device, send first telemetry in under 15 minutes. Azure IoT CLI extension for device management.