The REST & MQTT support uses the SLIP protocol over the serial port to enable the attached microcontroller to initiate outbound connections. The REST support lets the uC initiate simple HTTP requests while the MQTT support lets it communicate with an MQTT server bidirectionally at QoS 0 thru 2.

The MQTT support is in the form of a built-in client that connects to a server using parameters set below and stored in esp-link's flash settings. This allows esp-link to take care of connection parameters and disconnect/reconnect operations.

The MQTT client also supports sending periodic status messages about esp-link itself, including WiFi RSSI, and free heap memory.