Chapter 12. MQTT (experimental)

Table of Contents

MQTT is a protocol that is designed to allow IoT (Internet of Things) devices to communicate - for example smart light switches, sensors, and all sorts of home automation.

To communicate, these devices connect to a broker which acts as a hub / switchboard to relay messages. The FB2900 can operate as an MQTT broker, allowing your IoT devices to communicate in a typical home or office.

12.1. Limitations

As with any broker, there are limitations to the operation. As an embedded device, the FireBrick is designed to ensure reliable operation, and so has some specific limitations to its operation. However, as with any FireBrick feature, if these are a problem for your use case, please do let us know.

Maximum message size (2000 bytes).
Maximum connections (300), including connections which are idle but have state or retained messages.
Maximum messages in flight (10000), including retained and will messages.
Maximum subscriptions per connection (100).
Messages accepted and handshake for QoS 1/2, but are all demoted to QoS 0 for sending. As TCP is used messages are normally reliably sent, but this limitation greatly reduces complexity and state. Please let us know if this is an issue.
No retained state over reboot.


11.2. Definining PPPoE links		12.2. Features