Can a client subscribe to all topics available with broker?

Can a client subscribe to all topics available with broker?

Q- Can I get list of all topics on a broker? A- Not unless you subscribe to all topics and scan them.

How do I create a topic on MQTT?

Create a topic

1. To do so, click on the Topics tab, then click on the ‘+ New’ button.
2. Click on ‘Add’ to add the new topic.
3. In the topic list, click on the topic to view it.
4. You are now ready to put the STS MQTT service to work for you, creating additional clients and topics for your application!

How do I view MQTT messages?

In the Subscriptions list, choose my/topic to see the message. You should see the message appear in the MQTT client below the publish message payload window.

How do I check MQTT data?

Using the MQTT Monitor to view data to the MQTT Broker

1. Make a new connection with MQTT Lens.
2. Save your connection.
3. Subscribe to the “up” topic.
4. View the up-going data.
5. Subscribing to the “down” topic to see bidirectional MQTT, commands to your device.
6. The MQTT Monitor in use.

What is MQTT port?

TCP/IP port 1883 is reserved with IANA for use with MQTT. TCP/IP port 8883 is also registered, for using MQTT over SSL. You can pass a user name and password with an MQTT packet in V3. 1 of the protocol.

Can a device subscribe to multiple MQTT topics?

One of the strengths of MQTT is that a device can subscribe (or publish) to multiple topics. The broker will sort things out. Even though my first example only showed one, it is straight forward to get the Arduino PubSubClient library to subscribe to Multiple MQTT topics.

How does the MQTT broker decide which message to send?

As we have already mentioned, the MQTT broker uses the topic of a message to decide which client receives which message. We also look at SYS-topics, which are special topics that reveal information about the broker itself. Be sure to watch our video about MQTT topics at the end of this blog post. Let’s get started.

What are the different types of wildcards in MQTT?

There are two different kinds of wildcards: single-level and multi-level. As the name suggests, a single-level wildcard replaces one topic level. The plus symbol represents a single-level wildcard in a topic. Any topic matches a topic with single-level wildcard if it contains an arbitrary string instead of the wildcard.

Is the$ SYS topic read only in MQTT?

The $SYS topic This is a reserved topic and is used by most MQTT brokers to publish information about the broker. They are read-only topics for the MQTT clients. There is no standard for this topic structure but there is a guideline here that most broker implementations seem to follow.