Internet-Security.com TCP port 8883 details

TCP port 8883 is the standardized port for MQTT over TLS/SSL (often called MQTTS).
MQTT brokers such as Eclipse Mosquitto, HiveMQ, EMQX, and VerneMQ commonly expose their secure listener on 8883.
AWS IoT Core accepts device connections using MQTT over TLS on port 8883.
Microsoft Azure IoT Hub supports native MQTT clients over TLS on 8883 (with 443 as an alternative via WebSockets).
IBM Watson IoT Platform and Eclipse’s public Mosquitto test server (test.mosquitto.org) provide MQTT TLS access on 8883.
Home Assistant (Mosquitto add-on) and openHAB deployments use 8883 for encrypted MQTT traffic between devices and controllers.
Embedded/IoT devices (e.g., ESP32/ESP8266 using Eclipse Paho or AsyncMqttClient) often connect to brokers on 8883 when TLS is enabled.
Security note: attackers and botnets have been observed scanning and brute-forcing MQTT brokers on 1883/8883 to abuse weak or unauthenticated configurations.

TCP 8883