Azure IoT Hub Troubleshooting

Common issues and solutions for your IoT deployments.

Troubleshooting Common Azure IoT Hub Issues

This section provides guidance on diagnosing and resolving common problems encountered when working with Azure IoT Hub. We cover connectivity, device management, messaging, and security issues.

Connectivity Problems

Device Not Connecting

Symptoms: Devices report connection failures, or the device status in the IoT Hub portal shows as disconnected.

  • Check Credentials: Ensure the device connection string or SAS token is correct and hasn't expired.
  • Network Accessibility: Verify that the device can reach the IoT Hub endpoint (your-iot-hub.azure-devices.net) over the required ports (e.g., 443 for MQTT/HTTPS, 8883 for AMQP).
  • Firewall/Proxy: Check if any firewalls or proxies are blocking outbound connections.
  • Device Time: Ensure the device's clock is synchronized, as time drift can cause authentication issues.
  • IoT Hub Quotas: Review your IoT Hub's message limits and connection limits to ensure you haven't exceeded them.

Tools: Use tcping or telnet to test network connectivity. Check Azure Monitor logs for detailed error messages.

Intermittent Disconnections

Symptoms: Devices connect successfully but disconnect frequently.

  • Keep-Alive Settings: Ensure the device SDK's keep-alive intervals are appropriately configured for your network environment.
  • Device Resource Constraints: Low memory or CPU on the device can lead to dropped connections.
  • Network Instability: Unreliable network connectivity between the device and IoT Hub.
  • IoT Hub Throttling: If sending too many messages too quickly, IoT Hub might throttle connections.

Tools: Monitor device resource usage. Analyze network latency and packet loss.

Device Management Issues

Device Identity Not Found

Symptoms: Devices fail to authenticate, or the IoT Hub portal does not list the expected device.

  • Device Registration: Confirm that the device has been registered in IoT Hub with the correct Device ID.
  • Connection String Accuracy: Double-check the connection string used by the device matches the one for its registered identity.
  • Case Sensitivity: Device IDs are case-sensitive.

Tools: Use Azure CLI or Azure portal to verify device registration.

Twin Operations Failing

Symptoms: Desired properties are not updated on the device, or reported properties are not visible in IoT Hub.

  • Device SDK Version: Ensure you are using a compatible and up-to-date version of the IoT device SDK.
  • Device Connectivity: The device must be connected to IoT Hub to receive desired property updates or send reported properties.
  • Serialization Issues: Verify that twin property updates are correctly serialized (e.g., as JSON).

Tools: Inspect device logs for twin update acknowledgments or errors.

Messaging Problems

Messages Not Reaching IoT Hub

Symptoms: Telemetry data is not appearing in IoT Hub or downstream services.

  • Device SDK Event Sending: Ensure the device code is correctly calling the send telemetry function.
  • Message Format: Verify that messages adhere to the expected format and size limits.
  • Authentication/Authorization: The device must be authenticated to send messages.
  • IoT Hub Quotas: Check if message quotas have been reached.

Tools: Use device-side logging to confirm messages are being sent. Monitor IoT Hub metrics in Azure Monitor.

Command/C2D Message Not Received by Device

Symptoms: Commands sent from IoT Hub are not being processed by the device.

  • Device Connectivity: The device must be connected to receive C2D messages.
  • Device SDK Message Handling: Ensure the device application is properly registered to receive C2D messages and is handling them.
  • Message Delivery Policy: For persistent C2D messages, ensure the device acknowledges receipt.

Tools: Implement logging on the device to track incoming C2D messages.

Security Issues

Authentication Failures

Symptoms: Devices are repeatedly denied connection due to authentication errors.

  • Connection String/Key Validity: Ensure the primary or secondary keys used in the connection string are correct and haven't been rotated without updating the device.
  • X.509 Certificate Issues: If using X.509 certificates, verify the thumbprint, certificate chain, and expiration date. Ensure the device's certificate is trusted by IoT Hub.
  • SAS Token Expiration: If using SAS tokens, ensure they are generated with a valid expiry.

Tools: Check IoT Hub diagnostic logs for specific authentication error codes.

For more advanced troubleshooting, consult the Monitoring and Diagnostics guide.