Legacy MQTT.fx downloads and MQTT testing guides
Understand MQTT brokers and test them with a desktop client.
An MQTT broker accepts client connections, receives published messages, matches topic filters, and forwards messages to subscribed clients.
Common ports are 1883 for MQTT over plain TCP and 8883 for MQTT over TLS. Some platforms also expose MQTT over WebSocket for browser-based clients.
Use a desktop client such as MQTT.fx, MQTTX, or MQTT Explorer. Connect with the broker host and port, subscribe to a topic, publish a payload, and verify delivery.
For production systems, test authentication, TLS certificates, retained messages, QoS behavior, offline sessions, and topic permission rules separately.
An MQTT broker is the server that receives messages from publishing clients and forwards them to clients subscribed to matching topics.
Port 1883 is the common default port for MQTT over plain TCP. TLS-secured MQTT commonly uses port 8883.
It can store retained messages and session state depending on configuration. Long-term message storage depends on the broker product and persistence settings.