Azure IoT Hub

Connectivity Issues

This section covers common problems related to devices connecting to or maintaining a connection with Azure IoT Hub.

Device Cannot Connect

If your device is unable to establish an initial connection to IoT Hub, consider the following:

• Network Configuration: Ensure the device has proper network access to the IoT Hub endpoint. Check firewalls, proxies, and DNS settings.
• Connection String: Verify the device connection string is correct and hasn't expired or been revoked.
• TLS/SSL Certificates: Ensure your device's operating system or firmware has the necessary root certificates to establish a secure TLS connection.
• IoT Hub Status: Check the Azure Status page for any ongoing issues with IoT Hub in your region.

Intermittent Disconnections

Frequent disconnections can be caused by several factors:

• Network Instability: Unreliable network connections on the device side.
• Heartbeat Timeout: The device may not be sending keep-alive messages regularly enough, causing IoT Hub to close the connection.
• Resource Constraints: The device might be running out of memory or CPU, leading to application instability and disconnections.
• Throttling: If your hub is experiencing high load or exceeding quotas, connections might be affected.

Authentication Failures

Problems authenticating your device with IoT Hub.

Invalid Credentials

Authentication failures often stem from incorrect credentials.

• Shared Access Signature (SAS) Tokens: Ensure the SAS token is correctly generated, signed with the correct key, and has an appropriate expiry time.
• X.509 Certificates: Verify that the device's certificate is valid, trusted by IoT Hub, and hasn't expired. Ensure the private key is securely stored.
• Symmetric Keys: Double-check that you are using the correct primary or secondary symmetric key.

Certificate Validation Errors

If using X.509 certificate authentication, you might encounter errors if:

• The device certificate is not trusted by your IoT Hub.
• The certificate has expired or is not yet valid.
• The certificate's subject name or Subject Alternative Name (SAN) does not match the IoT Hub hostname.

Message Delivery Problems

Issues with messages sent from devices to IoT Hub or vice-versa.

Device-to-Cloud (D2C) Messages Not Appearing

If your device sends messages but they don't appear in IoT Hub:

• Message Acknowledgement (Ack): Check if your SDK is configured to request message acknowledgements. This helps verify delivery to IoT Hub.
• Routing Rules: Ensure your message routing rules are correctly configured to send messages to the intended endpoints (e.g., Storage, Service Bus, Event Hubs).
• Message Properties: Verify that messages have the correct content type, encoding, and any required custom properties.
• IoT Hub Quotas: Monitor your IoT Hub's message quotas. Exceeding them can lead to messages being dropped.

// Example of sending a D2C message with acknowledged delivery (concept)
client.sendEvent(message, (err, res) => {
    if (err) console.log('Error sending message: ' + err.toString());
    else console.log('Message sent. Status: ' + res.constructor.name);
});

Cloud-to-Device (C2D) Messages Not Received by Device

If C2D messages are sent from IoT Hub but not processed by the device:

• Device Online Status: Ensure the device is connected and online when the message is sent. C2D messages can be queued if the device is offline, but there are limits.
• Device SDK Implementation: Verify that your device application is actively listening for and processing incoming C2D messages.
• Message Acknowledgement (Ack): The device needs to acknowledge receipt and processing of the C2D message back to IoT Hub.
• Service Endpoints: If using Service Bus or Event Hubs for C2D, check their status and configuration.

Device Management Errors

Troubleshooting issues related to device twins, direct methods, and reported properties.

Device Twin Updates Not Reflecting

If desired properties set in the cloud are not being updated on the device, or reported properties from the device are not visible in the cloud:

• Device Connectivity: The device must be connected to receive desired property updates and send reported properties.
• Device SDK: Ensure the device application correctly handles twin synchronization events.
• Update Logic: Review the code that updates desired properties on the device and reports properties back.
• Throttling: Excessive twin updates can be throttled.

Direct Method Calls Failing

Problems executing direct methods on devices:

• Device Online: The device must be connected to receive and execute direct method calls.
• Method Name Mismatch: Ensure the method name invoked from the cloud exactly matches the name the device is listening for.
• Payload Format: Check the JSON payload for correctness.
• Device Response: The device must respond to the direct method call with a success or error status.

Azure IoT SDK Specific Errors

Common errors encountered when using Azure IoT SDKs.

• SDK Version Compatibility: Ensure you are using a supported and compatible version of the SDK for your platform.
• Dependency Issues: Check that all required libraries and dependencies are correctly installed.
• Configuration Parameters: Verify that all SDK configuration parameters (like connection string, retry policies) are set correctly.
• Memory Leaks: In long-running applications, check for potential memory leaks within the SDK or your application code.

Performance Bottlenecks

Addressing slow performance or high latency with IoT Hub.

• IoT Hub Tier: The selected IoT Hub tier (e.g., Free, Basic, Standard) impacts throughput and connection limits. Consider scaling up if you are hitting limits.
• Device Processing Load: If devices are slow to process messages or perform operations, it can impact the overall system.
• Network Latency: Physical distance between devices and IoT Hub, or network congestion, can contribute to latency.
• Efficient Telemetry: Optimize telemetry data by sending only essential information and using efficient serialization formats.
• Batching: Send telemetry data in batches where appropriate to reduce the number of individual requests.

Understanding Throttling Errors

IoT Hub has quotas and limits to ensure service availability. Exceeding these can result in throttling.

• Device-to-cloud (D2C) message limits: Per device and per hub.
• Cloud-to-device (C2D) message limits: Per device.
• Direct method call limits: Per hub.
• Device twin operations: Updates and reads.

When throttled, you will typically receive HTTP status codes like 429 Too Many Requests.