MQTT Explorer – “Disconnected from Server”

Course Module: EHEv1 – Module 10: Introduction to IoT
Tool Affected: MQTT Explorer
Error Message: "Disconnected from server"

🧩 Description

While attempting to connect to test.mosquitto.org using MQTT Explorer, students may encounter the error:

Disconnected from server

This issue prevents users from completing the MQTT connection portion of the lab.

🧠 Root Cause

The issue is typically caused by a temporary outage or rate limit on the public MQTT broker test.mosquitto.org. As this is a third-party public service, it may occasionally be unresponsive due to high traffic, maintenance, or IP-based limits beyond EC-Council’s control.

✅ Resolution Steps

1. Wait a few minutes and try again. A temporary issue may resolve itself.

2. Relaunch the lab to start a fresh session and attempt the connection again.

3. Try a different public MQTT broker (using the same port and encryption settings):

   • mqtt.eclipseprojects.io

   • broker.hivemq.com

4. Ensure you are using Port 1883 and that encryption is disabled, per lab instructions.