Publishing

Send a message back from Publish at the bottom of the right panel.

1. Enter a Topic, select one in the tree, or right-click a row and choose Publish here.
2. Enter the Payload; Format JSON tidies valid JSON or reports Not JSON without changing it.
3. Choose QoS and Retain, then Send.

Send requires a connection. Queued to <topic> confirms queuing, not delivery; MQTT 5 broker rejections appear in the status bar. The message appears in the tree when the broker delivers it to a matching subscription.

Topics cannot be empty or contain + or #. Errors below the form explain rejected input, including messages over the packet limit.

MQTT 5 properties

Set Content type or choose Add user property for a key/value pair; the minus button removes a pair. These fields are hidden and ignored on MQTT 3.1.1.

Recent messages

Recent keeps up to 20 distinct queued messages within 64 KiB of text; larger entries are skipped. Choose one to restore its topic, payload, QoS, retain flag and properties.

Uncheck Remember publish history to keep it only until the app closes, or choose Clear history to empty it.

Clear retained messages

To clear a retained message, rstmqtt publishes an empty retained payload on its topic. While connected, right-click a topic and choose:

• Clear retained for that topic.
• Clear retained below… for that topic and its descendants, with a count and confirmation first.

The status bar reports what was queued.

Subtree clearing only includes topics this client has seen with a retained flag. On MQTT 3.1.1, retained publishes received after subscribing lack that flag and may be missed. Unsubscribed topics stay untouched.