Internet-Security.com TCP port 1883 details

TCP port 1883 is the default port for the MQTT publish/subscribe protocol.
Common MQTT brokers that listen on 1883 include Eclipse Mosquitto, EMQX, HiveMQ, and VerneMQ.
Home automation uses it widely: Home Assistant’s Mosquitto add-on, openHAB’s MQTT binding, Node-RED MQTT nodes, and Zigbee2MQTT typically connect to a local broker on 1883.
Cloud MQTT services such as CloudMQTT (and some HiveMQ Cloud setups) offer non‑TLS MQTT endpoints on 1883 for development or private networks.
Device firmware/projects like Tasmota, ESPHome (ESP8266/ESP32), and Shelly devices in MQTT mode default to brokers on 1883 unless changed.
Industrial deployments (e.g., Inductive Automation Ignition with Cirrus Link Sparkplug B modules) use MQTT to brokers like Mosquitto/EMQX on 1883 inside plant networks.
Security: exposed, unauthenticated MQTT brokers on 1883 are commonly abused—attackers can subscribe/publish, exfiltrate telemetry, or send control commands; such incidents often stem from misconfiguration or exploitable broker setups.
Many managed IoT clouds require TLS MQTT on 8883 for internet access but interoperate with on-prem 1883 brokers.

TCP 1883