1883
Lightweight publish-subscribe messaging for IoT devices (MQTT)
Message Queuing Telemetry Transport
What is port 1883?
MQTT on port 1883 is a lightweight publish-subscribe messaging protocol designed for IoT devices with limited power and bandwidth. It is used by smart home devices, industrial sensors, and telemetry systems. The connection is unencrypted — use MQTT over TLS (port 8883) for any internet-facing deployment. Thousands of open MQTT brokers on the internet inadvertently expose sensitive IoT data including sensor readings and control commands.
Quick checks
$
nc -zv example.com 1883
$
nmap -p 1883 example.com
$
telnet example.com 1883