MQTT and HTTP protocols

Owned by Aaron Allsbrook
Last updated: Feb 21, 2024 by Jeff Slavin
2 min read

ClearBlade IoT Core supports device MQTT and HTTP connection and communication protocols. Devices communicate with ClearBlade IoT Core across the MQTT or HTTP bridge. The MQTT/HTTP bridge is a central ClearBlade IoT Core component.

When you create a device registry, you select protocols to enable MQTT, HTTP, or both.

  • MQTT is a standard publish/subscribe protocol frequently used and supported by embedded devices and is also common in machine-to-machine interactions.

  • HTTP is a connectionless protocol: devices do not maintain a connection to ClearBlade IoT Core with the HTTP bridge. Instead, they send requests and receive responses. ClearBlade IoT Core supports HTTP 1.1 only.

How the protocols work in ClearBlade IoT Core:

MQTT bridge

HTTP bridge

MQTT bridge

HTTP bridge

Device connection is maintained

Connectionless (request/response)

Full-duplex TCP connection

Half-duplex TCP connection

JWT is sent in the CONNECT message’s password field

JWT is sent in the HTTP request’s Authorization header

Telemetry events are pushed to Cloud Pub/Sub

Telemetry events are pushed to Cloud Pub/Sub

Device connection status is reported

No device connection status reported

Device configurations are propagated via subscriptions

Device configurations must be explicitly requested (via polling)

Devices always receive the most recent configuration (whether newer or not) on subscription

Devices can specify that only newer configurations should be received

Device configurations are acknowledged (ACKed) when using QoS 1

No explicit ACK for device configurations

Last device heartbeat time is retained

No device heartbeat data

Protocol features:

MQTT

HTTP

MQTT

HTTP

  • Lower bandwidth usage

  • Lower latency

  • Higher throughput

  • Supports raw binary data

  • Lighter weight (easy to get started; simple curl commands)

  • Fewer firewall issues

  • Binary data must be base64-encoded, which requires more network and CPU resources

Both bridges use public key (asymmetric) device authentication and JSON Web Tokens (JWTs). For details, see the device security section.

If you need help determining which protocol is best for your use cases, start with HTTP to familiarize yourself with ClearBlade IoT Core. Then switch to MQTT if required.