MQTT and HTTP protocols

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
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
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.